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Concrete, as the most used building material worldwide has a huge impact on our cities, societies and environment. Much of our research is based on the idea to create an alternative solution for conventional methods of building, such as building with concrete. In this article, we will tackle basic and relevant knowledge and information about concrete, to understand why it is important to think about alternative solutions for the future of our building habits. This write-up will be part of a series of small papers related to meaningful knowledge, to understand why it’s urgent to rethink our conventional building approaches.

Concrete, cement & mortar – definitions

To give a brief overview of what we are talking about in specific, we will first define the most important terminologies that we will need to understand the whole topic around concrete.
Four important terms you should know about and understand their exact definitions: 

Typical composition of concrete

cement  // səˈment

Cement is the key ingredient to mix concrete. This product is mainly made out of crushed limestone mixed with shales and slates, shredded to a fine powder and heated up to approximately 1450°C. The heat causes a chemical reaction, also known as calcination.[1] That reaction along with the heating process causes a high amount of carbon-dioxide emissions, which makes cement production a big driver of greenhouse gas emissions. The entire process happens in a giant mixer, called a cement kiln. [2] The most popular kind of cement is portland cement, developed in England in the early 19th century. [3]

concrete // ˈkänˌkrēt

Concrete is an artificial building material, which consists of a binding agent like cement or lime, in addition to water and aggregates (sand and gravel) as well as potential  additives (like fly ash or plasticizers). The cementitious part gets liquified with water. By adding water to the cement a chemical reaction is caused and the process of crystallization begins. In the next step some additives such as gravel and sand are added. These aggregates are held together by the liquified cement. Once the whole mixture is cured, this process will finish with a solidified product, called concrete.

mortar // ˈmôrdər

Mortar is a workable paste, used to bind bricks, stones or to fill gaps and holes. The basis is made out of a binding agent (such as slaked lime, ash or, most commonly nowadays, cement) added with water and a fine aggregate, mainly sand. 

Mortar is one of the oldest building materials, used for many thousand years. For a long time, slaked lime, volcanic ashes or clay worked as a binding agent. During the nineteenth century portland cement was invented. From that time cementitious mortar rose in popularity and replaced the old binding products.

These two kinds of mortar differ in two ways. On the one hand cementitious mortars usually are more workable due to faster curing, higher water resistance and less cracking, on the other hand non-cementitious mortars significantly cut greenhouse emissions while processing. It even can absorb CO2, which appears to happen when lime mortar cracks, so that air (especially CO2) can be absorbed. By absorbing CO2, lime mortar is even molding and gets even stronger.[4] To put it plainly:  it’s an environmentally friendly and more sustainable alternative.

reinforced concrete // ˈˌrēinˈfôrst ˈkänˌkrēt

In most cases concrete is combined with steel rebars, to compensate for the low tensile strength. The capability of concrete to react on compressive load is ten times bigger than the capability to bear tension loads.[5]

A more advanced and further developed version of conventionally reinforced concrete is prestressed concrete. To make concrete structures more durable against tensile forces, tendons, a high performing kind of rebar gets tensioned. Mainly these tendons are wires or threaded rebars. When applying in the casted concrete, the concrete part gets compressed, which gives the structure a higher performance, while being in service. [6]

Why is cement concrete so popular?

There are many reasons for its popularity: its liquid stone characteristics were revolutionary and created the possibility to make nearly every form out of concrete.

Cement concrete structures can be segmented and precast, making it suitable for big construction projects; and once solidified, it is a very strong material with the ability to bear high amounts of load. Designers adopted the versatile material, and nowadays we find furniture and accessories made of this material, in every kind of shape.

The use of concrete can be dated back to the ancient times. Romans mastered the use of hydraulic lime as a binding agent, called “opus caementicium”. After the fall of the Roman empire, the use of concrete faded, till it got resurrected in the early 19th century. Instead of using hydraulic lime, portland cement, a further development of the ancient version, was invented and led to a big rise in popularity of concrete in building industries. The first buildings during this time were bridges, foundations and harbours, facilitated by the compressive strength and workability of the new material.[7] 

In the late 19th century iron rods, and later steel rebars, were added to poured concrete to increase tensile strength. It was mainly developed by the French Joseph Monier [8]  – an invention which is ubiquitous in building industries nowadays. This invention led to a big rise in popularity in the residential and social housing sector. In comparison to conventional houses in those days, new concrete based housing projects were more durable, termite and fire resistant. The workability of concrete made it fast and easy to use on site. Pre-castable and serial development of construction elements cut costs significantly. In the 50s of the last century, concrete played a major role in evolving the architectural style of Brutalism, a socio-aesthetically driven architecture movement of showing raw, honest constructions often used for big scale civic and public projects. This architectural style was a dominating force during the next two decades. [9]

In addition, the raw materials of concrete are available in large quantities around the globe, which makes concrete cheap to produce. Limestone, sand and gravel are quite cheap. The main processing costs are caused by the cement production. 

What quantity of resources are needed to produce cement concrete?

There are four main components of cement concrete (cement, water, sand and gravel). For reinforced concrete, there is an additional component – steel. Besides these materials, there are more raw resources needed to produce the main ingredients. To produce one tonne of cement, approximately two tonnes of raw limestone are necessary. [10] The production of cement is a high energy consuming process. One ton of cement takes about 120 kWh of energy in process heating. This energy is mainly obtained from fossil fuels and burning waste. [11]

The cement concrete recipe

There are several different recipes for making concrete. The recipes mainly differ in the ratio of cement and the added aggregates. Concrete can be mixed with different ratios to get a higher load bearing capacity or to get a higher ability to withstand different exposures, such as seawater, moisture or frost.

The following recipes just give you a basic overview about how a classic mixture of concrete could look like:
A standard concrete mix consists of 1 part water (7,7%), 2 parts cement (15,4%) , 4 parts sand (30,7%) and 6 parts gravel (46,1%). [12] 

The higher the load the more cement you’ll need (f.e. a concrete column, foundation needs 1 part water (11,1%), 2 parts cement (22,2%), 2 parts sand (22,2%) and 4 parts gravel (44,4%) ).
Around 70% of the built concrete constructions are reinforced with steel, so you would usually have to add a certain percentage of steel rebars to the produced concrete (60-80 kg/m3 of concrete).[13]

That means a ton of average concrete consists of:

77 kg of water (7,7%)154 kg of cement (15,4%)307 kg of sand (30,7%)461 kg of gravel (46,1%)

Components of 1 tonne of concrete

Where is concrete used?

The use of cement concrete has various fields of application in construction and design. Since it was developed in the early XIXth century as a powerful structural material, it can be found in several constructive elements. The constructive elements made out of concrete can be summed up in three main categories:

massive built horizontal and vertical load bearing elements such as foundations and walls, used for small to middle scale buildings, such as residential housing.filigree skeleton construction elements, such as pillars and beams, mainly found in high rise buildings and large scale commercial buildingsspecial construction elements for infrastructural and exceptional building typologies, such as bridges, tunnels, dams or bunkers.

Where is concrete useful?

Nowadays concrete is used in many different ways. All constructive elements can be made in concrete and in most cases they are realized with this material.
But is it really necessary to replace other common construction methods with concrete?
It makes sense to use concrete in constructions, where load bearing elements have to bear big compressive strengths. A high rise a few hundred meters high? A tunnel? A dam? For sure! – There are fields of application, where no other material performs as well as concrete but in many cases concrete is used in small scale projects, where it is unnecessary and over proportioned.

How sustainable is cement concrete?

Concrete is certainly one of the building materials which gives a nearly unlimited range of use. As mentioned before, there are many upsides to using concrete. But there are always two sides of the coin.

A general definition for sustainability is meeting the needs of the present without compromising the ability of future generations to meet their needs. Sustainability is often discussed in environmental terms. It can also be related to two other important topics: society and economy.

Obvious and hidden impacts on our environment

Pie chart comparison between countries CO2 emissions and cement production

The impact on our environment caused by the cement industry and by building with concrete is enormous. The production of cement is a high energy consuming process. This energy is mainly obtained from fossil fuels or burning waste [14] In addition the chemical process of producing cement releases one molecule of carbon-dioxide per each molecule of calcium silicate hydrate. For each ton of produced cement, one ton of CO2 is emitted just by chemically processing it [15] Besides the vast amount of carbon dioxide emitted, many other hazardous air pollutants such as NOX or PM10 are emitted during the process. [16]

Cement is just one part of concrete. The added aggregates, such as gravel and sand, are mined in humongous amounts to cover the demand of concrete industries. Many environmental systems are suffering from negative effects such as land loss by erosion, destruction of natural habitats, sealing and contamination of soil. Some of these aggregates, especially sand, have to be shipped around the world to service demands. [17] Just to give a short glimpse of one of the biggest cruxes in world of the concrete industries – new developing middle-east states, such as the United Arab Emirates or Qatar have to import big amounts of sand to service their huge demand in building industries, despite the fact that cities like Dubai or Qatar are located in the middle of sandy deserts. [18] However, not all of the sand we can find on the globe is suitable for concrete production; desert sand is too fine and round to be used as an aggregate. [19]
Furthermore, concrete production is a thirsty industry. It needs almost 10% of annual industrial water withdrawal, and 75% of the concrete production takes place in regions which are already facing water stress and drought. [20]

Beside this, the impact on society has to be emphasized. The internationalization of architecture and modern building technologies have a negative influence on vernacular building technologies and local architecture. New buildings tend to be built in a modern way with modern materials, such as concrete. Cost efficiency, the establishment of new building technologies and the time aspect are reasons for a significant decrease of traditionally built projects. 

Impact of globalization and industrialisation on building traditions.

Comparison between the use of concrete and other building materials

One of the main issues caused by that situation is the loss of building knowledge and traditions. Traditional building techniques are being replaced by modern approaches. Around the world, houses and cities have been built according to local tradition for centuries. Now, knowledge that was gained in a long and enduring process is about to get lost in a few decades. 

Main drivers for the loss of vernacular architecture are caused by the growing globalization and industrialization of the world. Innovations in building technologies can be spread easily around a fully connected world. Rare materials not locally available can be easily shipped from anywhere – and they get transferred in humongous amounts around the planet. 

Downcycling cement concrete

The economic sustainability of concrete is always mentioned as a big pro. Nonetheless there are a few facts which are not properly taken into consideration. The production of concrete is cheap in comparison to other materials. A main reason for this, is that the aggregates you need to mix concrete are available in large quantities almost everywhere around the planet. But in recent times the local availability of certain components, such as sand are diminishing. [21] Our resources on the planet are finite, so using and monetizing resources as if they are infinite is unsustainable. To address this, the concrete industry tries to emphasize their product as recyclable, but to make it clear – concrete is not recyclableRecycling means, returning a material into a previous stage of a cyclic process. In case of the mentioned material, this is not completely possible. During calcination, the processing of the raw resource of limestone comes to a point of no return. Once cement is made, the process is irreversible. There is no commercially viable process to recycle it.[22] Recent reusing methods of concrete consist of shredding it and mainly using it as gritting material for infrastructural projects. In some cases this crushed concrete can be used as an aggregate to partly substitute gravel in concrete. Nevertheless these substitutes are small in numbers and in the end new concrete still requires additional water, cement, sand and gravel [23] Technically, the recent approaches to recycling concrete can be better named downcycling processes or a kind of mitigation. Many experts criticize the bigger potential of reusing shredded concrete for new concrete projects, [24] an effort which should be broadened in the future. 

Contradictive durability of concrete structures

Many proponents often mention concretes’ durability as a big pro. The use of concrete without adding any other materials (such as rebars, made out of metal) technically creates a very durable building material. Despite, most of the applied concrete is reinforced to be able to react on tensile stress. But the application of reinforced concrete in terms of durability is a contradiction in terms. Here nature inevitably can shorten the life span of buildings built out of reinforced concrete. Due to different thermal expansions and the inevitable inheritation of oxidation of the used steel rebars, concrete constructions suffer fast deterioration during their lifespan. Recent studies have shown that there is a 50% chance of reinforced concrete structures to not fulfill their service in terms of load bearing after just 35 years of use. [25]

What can be used instead of cement based concrete?

Concrete as a kind of fluid stone has found use in all fields of construction. But is it always necessary to use concrete? There are new materials and also tried and trusted methods of building which have mostly been replaced by concrete solutions. The replacement of conventional portland cement based concrete can cut greenhouse gas emissions and other environmental impacts significantly. Basically there are two main ways to avoid a humongous use of classic portland cement based concrete. The first one is to substitute or avoid the most polluting ingredient of classic concrete, portland cement. In a second scenario different building approaches with alternating materials or other building techniques can be applied.

Cement substitutes

First of all, portland cement based concrete mostly can be substituted by pulverized fly ash (PFA), which is a side product of coal burning processes. Another substitute with a big potential is Ground Granulated Blast-furnace Slag (GGBS), which is able to replace portland cement up to 90%. GGBS substituted concrete sets more slowly than concrete made with ordinary portland cement. The higher the amount of GGBS in the cement mix the longer it takes to cure. Besides this, a positive side effect of using GGBS substituted concrete is that it continues to gain strength over a longer period leading to improved overall durability and life expectancy. [26] Nevertheless the mentioned substitutes are by-products of other industries, such as coal, steel or aluminium production, which also have an enormous negative impact on our environment.

Green concrete

During the last decade several scientists started working on green alternatives for concrete. The most advanced approaches use micro organisms such as algae, bacteria or fungi for biocement production (CaCO3) by using the metabolic activity of these microorganisms. [27,28] Some of these bioproducts achieve similar specifics as classic portland cement and present a feasible and viable alternative to conventional portland cement based concrete.

lternative construction methods

Besides an ingredient-related replacement of conventional concrete, there are many tried and trusted construction methods which were applied in vernacular building styles and local architecture traditions. There is no convincing evidence that justifies concrete as the ultimate building material for most building tasks.

This table aims to present a series of more ecologically friendly solutions for common uses of cement concrete:

construction elementclassic building material
to be replaced / substitutedeco friendly alternative (not exhaustive)foundationsreinforced concretetyre foundation (for point foundations) [29]
gabion foundations [30]pillarsreinforced concrete
steelwooden constructions (bamboo, pine, GLT – glue laminated timber)
cardboard tubeswalls(reinforced) concrete
bricks
steel sandwich panelswooden constructions (CLT – cross laminated timber, framework constructions)
rammed earth (clay)
hempcrete
bricksflooringcement based screedclay 
wooden planks roofsreinforced concrete (flat roofs)
steel sandwich panelswooden constructions
thatched roofs
green roofs
hempcretepathingcement based pavement
asphaltnatural stone :
cobblestone, granite plastergypsum based plaster
cement based plastercardboard + lime plaster [31]
hempcrete plaster
straw clay based plaster

Conclusion

Concrete plays a major role in building industries. The further development of newly industrializing economies with huge demands on concrete are driving the ongoing trend of a growing concrete industry. Beside its advantages and big popularity, concrete brings a lot of negative impacts on global warming, environmental systems, building culture and social city development. It is important to mention that concrete lacks recyclability. The present system around the concrete industry can be summed up as a cradle-to-grave system. Resources are extracted, used and then wasted and dumped or downcycled in the best case scenario. Due to the chemical process, cement, the most important ingredient of conventional concrete, will never be recyclable, which underlines the unsustainability of a whole industry. Its fast and wide availability and low costs in production make it popular for many large scale projects. 

Nevertheless there are recent approaches to develop more sustainable alternatives to the classic portland cement-based concrete by trying to avoid or minimize the use of cementitious components, aiming for a better reusability and recyclability of resources. 

In addition, investigating forgotten vernacular solutions reopens fields of research to move forward to a more environmentally respectful architecture. Stay tuned on our continuous research, on social media and if you can and feel like supporting the initiative, make a small donation on our Patreon! 

Sources

[1] https://www.sciencedirect.com/science/article/pii/B978008034720250023X , opened 12.08.2020

[2] https://www.britannica.com/technology/cement-building-material/Extraction-and-processing , opened 12.08.2020

[3] https://www.screedscientist.com/portland-cement-a-brief-history/ , opened 18.08.2020

[4]  Quantitative Analysis of CO2 Uptake and Mechanical … – MDPIwww.mdpi.com › pdf , opened 23.09.2020

[5] https://diglib.tugraz.at/download.php?id=576a7195cc9f9&location=browse , opened 11.08.2020

[6] 372R-13 Guide to Design and Construction of Circular Wire-and-Strand-Wrapped Prestressed Concrete Structures , 2013

[7] Historic Concrete in Scotland Part 1: history and Developmentpub-prod-sdk.azurewebsites.net › api , opened 13.08.2020

[8] https://www.britannica.com/biography/Joseph-Monier , opened 13.08.2020

[9] https://www.architectureanddesign.com.au/features/list/a-look-at-brutalist-architecture , opened 20.08.2020

[10] http://ecosmartconcrete.com/?page_id=208 , opened 12.08.2020

[11] https://global-recycling.info/pdf/GLOBAL-RECYCLING_2-2019 , opened 11.08.2020

[12] https://www.marshalls.co.uk/gardens-and-driveways/blog/how-to-mix-cement-to-make-mortar-or-concrete

[13] https://diglib.tugraz.at/download.php?id=576a7195cc9f9&location=browse , opened 26.07.2020

[14] https://global-recycling.info/pdf/GLOBAL-RECYCLING_2-2019 , opened 11.08.2020

[15] http://ecosmartconcrete.com/?page_id=208 , opened 12.08.2020

[16] http://ecosmartconcrete.com/?page_id=208 , opened 13.08.2020[1] http://ecosmartconcrete.com/?page_id=208 , opened 13.08.2020

[17] https://www.globalconstructionreview.com/news/shifting-sands-concrete-hungry-singapore-orders-mi/ , opened 28.07.2020

[18] https://www.bbc.com/worklife/article/20160502-even-desert-city-dubai-imports-its-sand-this-is-why , opened 19.08.2020

[19] https://www.bbc.com/worklife/article/20160502-even-desert-city-dubai-imports-its-sand-this-is-why , opened 19.08.2020

[20] https://www.nature.com/articles/s41893-017-0009-5.epdf , opened 26.07.2020

[21] https://www.globalconstructionreview.com/news/shifting-sands-concrete-hungry-singapore-orders-mi/ , opened 29.07.2020

[22] CSI-RecyclingConcrete-FullReport.pdf , opened 29.07.2020

[23] https://www.archdaily.com/933616/is-it-possible-to-recycle-concrete, opened 30.07.2020

[24] https://eu-recycling.com/Archive/22163 , opened 30.07.2020

[25] https://www.structuremag.org/?p=9459 , opened 18.08.2020

[26] https://www.greenspec.co.uk/building-design/concrete-cement-substitutes/ , opened 25.08.2020

[27] https://www.mdpi.com/2071-1050/10/11/4079#abstract , opened 25.08.2020

[28] https://www.sciencedirect.com/science/article/pii/S2215017X18302923 , opened 25.08.2020

[29] https://criticalconcrete.com/tyre-foundations/ , opened 25.08.2020

[30] http://bristolgreenhouse.co.uk/site/foundations.html , opened 25.08.2020

[31] https://criticalconcrete.com/out-of-the-box-vol-3/ , opened 25.08.2020

The post The reality of concrete first appeared on Critical Concrete.
Did you miss our previous article…
https://concretedoctorsolutions.net/?p=164

Agriculture nowadays is one of the most harmful industries in the world. It is estimated that around one quarter of the world’s emissions is coming from this sector (1). If we were able to transform today’s techniques into a mindset and strategy that rather than exploiting the environment even has a positive impact on nature, we would be able to start regenerative processes on a big scale.

“We have disconnected ourselves from life on the planet, thinking that we are the intelligent ones.
But can’t see that we are just part of an intelligent system.”
from Ernst Götsch

Food…what?

A food forest, also called an edible forest garden, is a cultivation method that is inspired by a natural forest system and inhabits a large number of plants, ranging from vegetables and berry bushes to big fruit trees. Food forests benefit from the symbiotic interplay of the different plants and thus offer a large variety of crops without the need for intensive maintenance.

Pictures from Silver Leaf Farm, Skala, Greece
© Southern Lights Project

What is a food forest?

Conventional cultivation and gardening methods are exactly the opposite of what make the forest system work. In order to make the harvest easily accessible with large machines, only one species is cultivated in separate rows in each field. All dead organic matter is cleaned up and the missing nutrients are added through fertilizer or chemicals.

Plants disposition in a monoculture orange field
© Southern Lights Project

In a natural forest, plants automatically take up the space that is most suitable for them to receive the resources they need. Doing so, they also create or improve the habitat for other plants. The result is a deeply interwoven network of very different and complementary species benefiting from each other. Organic matter deriving from the plants and the plant’s fruit plays a crucial role in this circle. Left on the ground, it stores humidity and prevents the soil from drying out while it decomposes to nutrient-rich soil. In ideal circumstances, no human measures like additional nutrition or irrigation are required to keep this system working. The idea of ​​a food forest is not to reproduce a natural forest exactly but to have it as a guiding model for creating a resilient and productive structure that is adapted to our needs. This concept shows how the basics of the forestial system can be applied to agriculture. It mimics the main principles of a forest and consists of perennial trees and plants that provide food. They are planted in such a way that the layer they occupy in their original habitat is respected, providing the ideal conditions in regards to sunlight (2). Every operation is done in order to reach an energetic positive balance in the system, so the system regulates itself.

Pictures from Silver Leaf Farm, Skala, Greece
© Southern Lights Project

What are the impacts of a food forest?

On the one hand, a food forest rewards its creators with many advantages. Similar to natural forests, human intervention can be reduced to a minimum because the system is mainly self-regulating. With a well-designed system also the harvesting process is not necessarily more time-intensive than in monoculture. On a smaller scale, where a food forest is mainly used for self-sufficiency, the variety of products supports a healthy and balanced diet. On a larger scale, this variety of products spreads the financial risk across many types of income opportunities by breaking the dependency on one crop only. In addition, the positive impact of cultivation led by food forest principles goes far beyond personal advantages. It does not just enrich the local biodiversity of plants, but by creating a natural habitat it also increases the diversity of animals, especially insects. Farming in a food forest way can kick-start and facilitate processes to save and recreate endangered ecosystems. Furthermore, as the enriched soil, the organic matter, and the plants keep humidity and bring shade, a food forest has an enormous impact on balancing the microclimate. Thinking big, the wide-spread use of food forest principles in agriculture could lead to a considerable effect on the climate.

Lizard Eggs
Pictures from Silver Leaf Farm, Skala, Greece
© Southern Lights Project

The key principles of the food forest

Disposition of plants

The design of a food forest garden requires a long-term mindset with the attitude to look patiently into the future. In fact, the natural system takes some time to strike a balance between the species, the final forms of the plants and their proper growth. Nevertheless, it is possible to get fresh fruit and quick results from the smaller plants since the beginning of the process, as those take a short time to adapt and grow. These plants also help prepare the good soil and habits for larger plants.

A food forest garden is usually made up of layers of different plants that strategically help each other throughout their life. In good conditions, the plants themselves occupy the layer to which they naturally belong. In an agroforestry system, eight layers of plants usually have to be organized:

The Emergent layer is the tree layer that overtops the other trees, forming its crown above them. This shows us that they need maximum sunlight and do not tolerate shade. Usually, trees of this layer have only a few branches on the trunk, concentrating its growth on the crown where the sunlight is. Typical for this layer are the date palm, walnut, and pear trees.

The Canopy Layer is composed of large fruit trees, nut trees and leguminous species with large crowns that are providing a good amount of shade during the dry and hot period. Plants are not in competition for reaching good soil, but only for capturing sunlight: trees are actually able to adapt their shape and to grow in harmony with other species to reach the best light spot. Examples for plants of this layer are mulberry, olive, fig or apricot trees.

The Understory Layer consists of small fruit trees and nut trees. Species of this layer prefer a good amount of sunlight but tolerate some shade. Examples for this layer are almond, orange, plum, nectarines, pomegranates, and apple.

The Shrubs Layer is composed of trees that need to be protected from direct sun. Plants of this layer are hazelnut, most berry shrubs and bananas.

The Herbs Layer is composed of short herbaceous plants, often annual.

The Groundcover Layer contains grasses, creepers, and low growing plants that protect topsoil from erosion and drought. This layer slows the speed of raindrops to lessen their impact and protects the soil’s dedicated network of roots, sand, organic matter, and hyphae (fungal roots).

The Vertical Layer is composed of climber plants that grow up trunks and branches of the bigger trees.

The Roots Layer is really important because it pulls up minerals trapped in rocks to the plants: it is composed of tubers, rhizomes and bulbs.

Typical disposition of plants in a food forest system
Infographic: Critical Concrete

Thanks to the layered diversity of species, food-forest projects provide diversification of products over monoculture cultivations: each layer is in fact offering a specific variety of food in different seasons, from fruits and berries to tubers and mushrooms. In contrast to a monoculture, that requires the fixed distance between plants, agroforestry allows us to reach a much higher density of cultivation, as plants overlap in layers.

Pruning & organic matter

As mentioned before, food forests are designed to reproduce a sustainable and working forest system in which external help and additional human activities are limited, except one: pruning. “Chop and drop” is the key activity that provides the quantity of organic matter that becomes compost to fertilize the soil, extremely important to increase root activities and feed the plants. Pruning plants is also essential to help plants to breath, grow more and reach a good amount of sunlight, encouraging chlorophyll photosynthesis. The photosynthesis is pushing the mycorrhizae, a symbiotic association between a fungus and a plant, playing an important role in plant nutrition, soil biology and soil chemistry.

Pictures from Silver Leaf Farm, Skala, Greece
© Southern Lights Project

The fertilization of the soil is constantly influenced by the production of new organic substances: the pruned branches that remained on the ground become water collectors in the rainy season and release moisture and water in dry periods. Following food forest principles is a good way to fight the soil exhaustion on a small or large scale. In fact, the use of different plants determines a symbiotic interplay in the use of the soil and is balancing nutrition resources. Every kind of soil could be defined as a “good” one: what matters is the amount of organic matter that determines the continuous fertilization of the soil. The soil is, also, acting as a sponge being a water and minerals container. Understanding of the importance of organic matter for the water management of the system can be found in the following numbers: If the amount of organic matter in the soil is increased by only 1%, an additional of 175.000 liters per hectare of water can be stored in the soil.

Comparison between an arid soil (left) and good one (right) rich of organic matter
© Southern Lights Project

Interview with Sheila from The Southern Lights Project

Food Forest had been proven a successful phenomenon on a smaller scale on a personal as well as on a commercial base. An amazing example for a prosperous sustainable business is the food forest farm The Southern Lights in Skala, Greece. Based on the organic farm of her father, Sheila introduced food forest features into her place, now cultivating more than 80 crops from which the farm and its employees can have a reliable income.

What do I need to start a food forest?

“There is no minimum size, you can start a food forest on a spot as little as one square meter. It is helpful to have or gather some knowledge of the plants you want to put, especially their layer. And finally, you need to add a lot of organic matter..”

Are there any plants that are not so suitable for food forest?

Some plants might be not so easy to work with, like for example grains or rice and you will not get too much crop from this. But it is important to know your plants and things that might work out in some other conditions might not work out for yours.“

Should I be afraid of invasive species?

“If a species is invasive in your place, that means something is missing. Actually, those so-called “invasive” or pioneer species prepare the soil with their organic matter for other plants that have higher demands on the soil.”

Can I combine a food forest with animals?

“Animals can be very helpful for your food forest. They help to decompose the organic matter as they eat it and literally poop fertilizer. But I would rather keep my place welcoming to every species that feels comfortable in my place instead of bringing animals from outside.”

How can I know if my soil is good soil?

“Your soil should look like the soil in a forest, meaning you find a lot of organic matter on the ground, even if the very surface is dry, it is humid within deeper layers. And if you can find worms, mycelium and mushrooms it is a very good sign.”

What is the difference between “permaculture” and “food forest”?

Permaculture is a design technique, which can be applied to any kind of context. Its main ideas are Earth Care, People Care and Fair Share achieved through many principles, for example, to observe and interact or integrate rather than segregate. A food forest is a good example showing this principle being applied.”

Extract from her lecture, to see the whole presentation check our YouTube Channel

How to bring these principles to a larger scale?

A common prejudice concerning the adoption of the food forest concept to a larger scale might be the assumption that due to its unregulated structure, a forest-inspired agriculture might not be workable with large machines. But projects started and inspired by Ernst Götsch, a swiss botanist working in Brazil, had shown that large scale agriculture and the principles of a forest can go astonishingly well together.

He developed the concept of syntropic farming [Gr. syn, together with, trepein, to turn.]: usually, a minimum of 30 different species will be planted, taking into consideration their suitability to the local conditions, their ecophysiological function, their lifetime as well as the farmer’s productive goals. To make it workable with bigger machines and tools, most of the plants are cultivated in rows. In contrast to traditional farming, these rows not only consist of one single species, set apart for a few meters but follow the principles of agroforestry and food forests. These means, companion plants and trees from different layers are densely combined together to facilitate the supporting networks. Mostly fast-growing support species (like eucalyptus or mulberry) are mixed with income-generating fruit-bearing plants and trees. Natural processes are accelerated through heavy pruning of the support species in order to generate vast amounts of organic matter which will decompose to nutritious soil for the fruit trees and plants.

What all of them have in common is that the harvest is a side-effect of ecosystem regeneration, and vice versa – ecosystem regeneration is a side-effect of the efforts to produce a harvest.”
from Ernst Götsch

Bringing food forest to urban contexts

In view of the many advantages of a food forest, the question arises, how this principle could be brought into the urban context. Similar to existing gardening projects, food forests can contribute to make cities greener, bring communities together and reduce food transportation. The benefit of a food forest is that also perennial species are used. This means, once the structure of the food forest is in place, less work will be required than it may be the case with the replanting of annual vegetables. “Upgrade” existing urban gardening projects is a good start to bring the principles of a food forest into the urban environment, but also introducing it to the yards and gardens of school and kindergartens has been proven to be a good starting point so far.

But the most practical way to bring a food forest into the city is by starting one of our own! Thanks to the introduction to the concept and the following workshop from Sheila Darmos from The Southern Lights, our very own little food forest is growing in our workshop’s backyard.

Critical Concrete Food Forest, Porto, January 2020In this video she will guide you through the planting of the different layers to set up your own edible forest.

Sources

(1) [Hannah Ritchie, Max Roser] “Environmental impacts of food production”, January 2020, online available at: http://ijsetr.org/wp-content/uploads/2017/10/IJSETR-VOL-6-ISSUE-10-1364-1369. (Last accessed in June 2020).

[Sheila Darmos] “The Southern Lights Project”, lectures and workshop, January 2020, online available at: http://thesouthernlights.org/. (Last accessed in June 2020).

[Ernst Götsch] “Syntropic Farm Project”, online available at: https://agendagotsch.com/en/. (Last accessed in June 2020).

The post (Urban) Food Forest first appeared on Critical Concrete.
Did you miss our previous article…
https://concretedoctorsolutions.net/?p=159

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DISCLAIMER

[This article shows the development of the first step of a new prototype experimented in Critical Concrete. During the conception of the green roof, the structure was checked by a civil engineer who also advised us in the development of our wildest prototypes.]

Check out the video to see how we experimented with scrap tyres and compressed earth&gravel for a low-impact and concrete free building! 

Introduction 

In the progress of developing our green roof prototype we have been confronted with foundations in different ways. Seeking for alternatives it turned out that the old granite walls of the building, once reinforced by wooden beams, would be strong enough to carry the load of the new roof. You can read all about the refurbishment and reinforcing of the walls for the roof in our previous articles (walls-refurbishment 1.0, walls-refurbishment 1.1, how to build a stone wall).

The size of the new roof however, stretches out further than the fully loadable walls. For that reason, part of the roof needs a different kind of foundation.

Section of the green roof highlighting the parts supported by tyre foundations

Our Research

Throughout our research for alternatives to concrete, we stumbled over the tyre foundation. For us, it was very interesting since it is a low-tech solution which is composed only of scrap tyres filled with compressed gravel. Both components are easily accessible almost everywhere in the world.

Indeed, when tyres worn out, they become a waste which is not easy to handle. Recently, more processes that aim at recycling have been developed from which rubber, steel and textile fibers are obtained. Another solution is to reuse the tyres directly in a different context, thus avoiding more energy consumption for the transformation of the product.

Pile of trashed tyres

Worn out tyre reused in a new contextScrap tyres have already been tested in various cases in the construction field, for example to make the roadbed of the streets and referred to as mechanical concrete, a method widely used in the USA. One of the most known cases is the Earthship Biotecture concept autonomous houses developed by architect Michael Reynolds, in which earth-rammed automobile tyres are used for building the main retaining wall of the house. This technique is presented as the most appropriate method for its strength, economy and low need of technical skills.

Pictures by mechanicalconcrete.com (pictures on the left) and by earthship_biotecture (licensed under CC BY-NC-ND 2.0) (picture on the right)

The flexibility of the tyre can also offer durable protection in a seismic area. These foundations can indeed reduce the effect of seismic vibrations on the building on top of them and it can be used in every stable soil, even clay soil (for more information click here). Yet we couldn’t find any applications that fits exactly our needs. Many cases used the tyres to build walls, or wall-like foundations where the structure was resting without anchoring. Other examples used conventional concrete to fix some kind of anchoring sockets. As far as we know, our case, a structure with several punctual load bearing columns, has not been well documented yet.

Interested in using this technology in your project?

Critical Studio can help!

Learn More!

Our Approach

In our particular case, we designed two single stepped footings for two columns of the green roof.

Section and plan of the two single stepped footings for two columns of the green roof

One part of the green roof structure lies on a massive, structurally stable granite wall built in the 19th century, and the other part will lay on the new foundation. Since it is a prototype and it is not well known how the foundations will react to the heavy load, we decided to make the new part (15m2) independent of the rest of the roof previously built (120m2). This assembly required us to insert an expansion joint which allows movement due to ground settlement or other variations, expansion or contraction of building materials. It will also assist the observation of potential changes and reduce the risk of damaging the whole roof in the worst case scenario. Indeed, this technique has been used in England for at least 15 years. Research and experiments of the Holy Trinity Church Tulse Hill showed that they tyre stacks will hold a minimum of 1000 kN/m2 of load with no detected movement on the expansion but a compressive variation of only 3mm (to watch the video click here). The IUT of Grenoble made tests of loading tyre foundations from the Flexagone office: They applied the weight of pressure of 72 tons on the foundation, without any damage or detectable movement (for more information click here).

Additionally we consulted several engineers to check our structural conceptions. As we explained in former articles, the heavy loads on the roof – composed of the drainage layer, earth and plants – impacts the renovation process by its load of 600 kg/m2– 5.88kN/m2, including the dynamic load. Based on this information and our needs, we developed the concept of single stepped footings for columns. We calculated that each pillar should carry about 2400kg approximately. The foundation includes a socket which joins it with the wooden column.

Section of the Tyre Foundation

This connection is especially important while setting up the tyre and aligning the structure. Once the roof is finished, its own weight will hold its place. Below the foundation is a metal plate. On one hand, it distributes the forces on the soil and on the other hand it connects the foundation to the holding socket of the column. On top of the metal plate lay the tyres. We chose two tyres to make the foundation strong enough for the load. One truck tyre (95cm ø) and a smaller car tyre (65cm ø). The holding socket for the column is layed on the upper tyre and connected to the foundation through threaded rods which are welded to the base plate. The socket itself also holds the column in the right position.

Our workexplained step-by-step

This guide is an overview of every step we took in building our prototype of the tyre foundation. Since it was our first attempt, not all of our processes are optimized and need further development. However, this should serve as an inspiration for anyone with a similar situation and is open for discussion and improvement.

Beforehand a list of tools we used
in the progress:

welding machine,crowbar,grinder,hammer,wheelbarrow,bench drill,shovel,cutter.

Throughout each phase, we remind you that it’s important to protect yourself using appropriate safety equipment.

For this, you will need:

helmets,protective goggles,appropriate protective gloves,security shoes,reusable dust masks.

Preparation of the ground

The first and most important step before starting any foundation is the analysis of the ground. The soil has to have a sufficient bearing capacity. If the soil is not suitable there are different possibilities like reinforcing the soil, digging deeper, or adapting the foundation type to a wider tyre for example. In our case, we needed to dig until +/- 70 cm under the floor level to find a proper soil. We decided to put a layer of 5 cm of compressed gravel, frequently used under footings to have a correct level.

Estimated time: 6 to 8 hours per pit,
depending on the toughness of the ground

Leveling the ground of the pit

The base metal plate

The metal plate is the base of the foundation and serves as a solid surface for the tyres. We chose a thickness of 2 cm. To have the plate and also the column connected to the foundation we welded 4 threaded rods to the plate. The socket will be attached to these rods later on. Before putting the plate in the pit we put a breathable and waterproof membrane supposed to protect the plate from humidity in the ground. An EPDM membrane might have been a more suitable choice to increase the durability of the protection. We tried to wrap the plate as well as possible. Additionally, we painted the base plate and especially the weld joints with anti-corrosive paint. We still don’t know how this will react with the time, neither if it is going to be efficient enough to protect the welds. Our main objective is to take all the necessary precautions to avoid that water eventually permeates and settles at the bottom of the foundation. In our next tyre foundation build, we would consider drilling some holes in the metal plate to allow for the draining of water infiltration. The use of this metal plate was advised by our engineer to level the ground on which the foundation itself would set, but we didn’t find any other project using a similar precaution. It was also helpful for us to link the column to the foundation on a robust way.

Metal plate wrapped with membrane

Estimated time: 2 to 6 hours,
depending on accessible tools to cut the plate on the good dimensions

Metal plate on the ground of the pit

Preparation of the columns

The columns we used are made out of two 12×24 cm construction plywood beams. To join the two pieces we glued and screwed them together. The section is therefore 24×24 cm. To protect the wood from fire, water and pests we applied a layer of wood ash on the tyre, as well as protected the wooden column with a layer of borax, known as a protection against mold and repellent against insects. For a specific protection to prevent a specific termite attack, we paint the column with a mix of essential orange oil (5%) and linseed oil (95%). We will soon dedicate a detailed article to wood protection from fire, water and pests.

Estimated time: 2 hours.

Preparation of the socket

We used a steel socket to fix the column with the foundation. The socket is connected to the foundation with four threaded rods. It is fundamental to align properly the rods after putting the base plate, so that the columns would be aligned to each other. We used a wooden guide to secure the rods’ position while filling the tires. This guide is composed of two pieces that represent the two plates, with the holes for the threaded rods, and a long bar that helps to maintain them aligned and in place.

Metal plate on the ground of the pit

Estimated time: 4 to 6 hours,
depending on accessible tools to cut the steel and drill the holes.

Checking the alignment

Filling of the tyres

In its rawest form, the tyres can only be filled with earth. Lots of case studies for earth filled tyre foundations are in relatively dry climates where the temperature doesn’t go below 0°C. It is preferable to use an other sub-grade as gravel or other material to encourage drainage and allow for water expansion, and then avoiding some major instability in the ground caused by frost. We decided to choose gravel made of local accessible granite, from the North of Portugal. We had the choice of three sizes of gravel. After some discussions with our engineer, we decided to order the smallest to have better cohesion. We also added some sand to create a mix with better bonding and leave no empty space between the gravel. We used the ratio of two parts gravel to one part of sand (2:1). The mix in the tyres has to be then as compressed as possible. At first, the tyre can be filled with a shovel and by hands. When it is not possible to get any more of the mix in, a crowbar and a piece of wood can be used to open the tyre (see how they did at the Holy Trinity Church Tulse Hill). Once held open, a second person can continue to fill up the space with the mix. A piece of wood can be used to shove the mix in as deep as possible and a hammer to compress it. This needs to be done until the tyre is inflated and no more mix can be added. The foundation is now ready for the socket.

Estimated time: 6 hours for two people to fill the 2 tyres for one foundation
(a truck and a car tyre).

Installation of the socket

The steel socket which is holding the column is made out of three pieces of steel. The objective is to obtain a socket that correctly holds the column. We thought about different forms and finally settled with a “U”-form, that could maintain the feet of the columns and be correctly fixed to the lower part of the foundation.

Base plate

The first part being the base plate (30x30cm), which has four holes to be fixed with the threaded rods of the foundation. The holes of the plate have to line up with the position of the threaded rods and should be 1mm bigger than the diameter of the rods to facilitate their insertion. Our rods were 12mm diameter. The second part being the two steel brackets (15x20cm), which are welded to the plate and hold the column with two horizontal threaded rods. The individual steps of this process are explained below.

(1) The holes in both of the brackets, which should be shifted, can be drilled and should be at least 2-3mm bigger than the rods.

(2) Afterward, the first bracket can be welded on the base plate.

(3) The piece, that results from this step can be used to mark the position of the holes on the wood of the column. For this, half of the steel socket can just be laid on the column.

Image

(4) It might be necessary to cut a little edge of the column so there is some space for the weld. After marking the holes, they can be drilled also 2-3mm bigger than the rod. The bigger the holes are, the more room there is to adjust and compensate for potential inaccuracies.

(5) The next step is to find the right position for the second bracket. For this, the socket can be laid on the floor, and the column can be put on it. The rods can be stuck through the holes of the first bracket, the column and the second bracket, which is not fixed yet. Also, the bolts can be put on and tightened.

Column steel base plate sketch

(6) The second bracket should now touch the base plate and there should be no gap. If it doesn’t, any holes can be drilled bigger to make it fit properly. If it fits, it can be fixed by welding on 4-5 small points. Afterward, the column can be removed. The second bracket should be in the right position and can now be welded on completely.

Estimated time: 5 hoursto install the socket: drill, weld and adjust.

Installation of the columns

Once the socket is welded together in the “U”-form and the holes are drilled, the foundation is ready to receive the columns which have a section of 24×24 cm.Having an even level foundation is crucial and is something to pay extra attention to, during all the process. First, we used the spirit level to check the level of the lower plate, to ensure that the tyre will be placed on level ground. Indeed, it is important to keep in mind that the column will apply a heavy load that needs to be properly transferred to the foundation. For the next steps, the laying of the tyres and the fixation of the socket, make sure to always keep checking the level and the alignment of each foundation.

Checking the level of the metal plate

Estimated time: 2 hours.

Preparing the columns

The retaining wall

In our case, one of the foundations is positioned under the level of the earth, in an outside environment, that forced us to find a solution for the rainwater not entering inside the workshop space. A retaining wall has been constructed to withstand lateral pressure of soil, due to earth and rainwater. There are a lot of different retaining walls, used for different situations for example the gabion retaining wall or the cantilever retaining wall.

Building the retaining wall

In our case, we built a gravity retaining wall that depends on its self-weight only to resist lateral earth pressure. Commonly, this needs to be of large proportions because it requires a significant gravity load. We constructed the wall from granite stones that we had acquired from previous deconstruction of old walls. To protect the column from water infiltration, we bonded the stones with a lime mortar mix.

Furthermore, we plan to realize a drain which prevents rainwater from entering the basement. Parallel to the retaining wall, it will collect excess water and runs it through a pipe into a sump away.

Cost and Time Comparison

Since we are using the tyre foundation instead of a concrete foundation, the comparison of cost is a crucial point. For this reason we compare only the part of the foundation which is replaceable. The socket and the column are therefore not part of the comparison, since they are the same for both versions. We already pointed out the factor of sustainability, which is our driver in this matter. But what does this mean from an economical point of view? A tyre foundation in its simplest form is only made from dirt and scrap tyres and is therefore basically free. This method is suited for retaining walls and foundations that don’t require anchoring. Our Approach of a highly stressed single step footing which includes anchoring cost approximately 125€ compared to the concrete version of approximately 28€. As the calculation shows, the major cost factor is the metal plate which is also an open question for us. Its necessity is not completely clarified wherefore we are looking for alternatives which even out differences in price and make the single step foundation an economically competitive alternative.

It is to be added that the concrete should be mixed homogeneously by a cement mixer rather than by hand, and that welding the steel reinforcement takes some time as well and electricity, and quite a few welding electrodes. In terms of time, the concrete takes at least 7 days to set sufficiently for a foundation in order to set-up the column, but is faster to make, comparatively.

Conclusion

In the process of finishing the green roof, the application of the tyre foundation has been challenging but successful so far. It is carrying the roof structure but needs further observation as to how it will react under the full load of the green roof including soil and vegetation. To be able to observe any kind of movement we installed a measuring unit that we will control regularly.

Movement measurement

Sustainable Satisfaction? 

Concrete is an extremely popular material for construction and can be found in most parts of the world. Today concrete is the primary material used for foundations because of its many positive attributes: it is strong in compression, it is flexible as it can be poured into adapted forms and sizes, it can be applied in situ, it has good fire resistant qualities. However, the production of Portland cement, an essential constituent of concrete, leads to the release of significant amounts of CO2 and other greenhouse gases. Because of limited natural resources, such as sand, and the output of greenhouse gases, concrete production is not sustainable and therefore requires alternatives in the construction field. A possibility is to use recycled materials which have low energy costs, high durability and low maintenance requirements and therefore a small impact on the environment.

The single step footing foundation represent a viable and affordable alternative method we are looking forward to developing and using in further projects.

You want to see more? Check out the video to see how we experimented with scrap tyres and compressed earth&gravel for a low-impact and concrete free building! 

Sources

[Ar. Bindu agarwal, Ar. Aanchal Sharma] “Reuse of Waste Materials: A case study of Earthships”, in: International Journal of Science, Engineering and Technology Research (IJSETR) Volume 6, Issue 10, October 2017, [Online] available at: http://ijsetr.org/wp-content/uploads/2017/10/IJSETR-VOL-6-ISSUE-10-1364-1369.pdf (Last accessed in December 2019).

[Architecture 2030] “Buildings generate nearly 40% of annual global GHG emissions”, [Online] available at architecture2030.org/buildings_problem_why/ (Last accessed in December 2019).

[Andrew, Robbie M.] “Global CO2 emissions from cement production, 1928–2018”, CICERO Center for International Climate Research, [Online] available at: https://www.earth-syst-sci-data-discuss.net/essd-2019-152/essd-2019-152.pdf (Last accessed December 2019).

[Decorex Pro] “Technology for the construction of the foundation of tires”, [Online] available at: /en.decorexpro.com/fundament/iz-pokryshek/ (Last accessed in December 2019).

[Department for Business, Innovation and Skills London] “Estimating the Amount of CO2 Emissions that the construction industry can influence”, [Online] available at: https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/31737/10-1316-estimating-co2-emissions-supporting-low-carbon-igt-report.pdf (Last accessed in December 2019).

[Deva Racusin, Jacob; McArleton, Ace] “The Natural Building Companion: A Comprehensive Guide to Integrative Design and Construction”, 2012

[Flexagon Office] “Fondations et plots”, in: La Maison Ecologique 67 – fevrier et mars 2012, [Online] available at: http://yourtes.net/fichiers/Fondations%20et%20plots%20-%20La%20Maison%20Ecologique%2067%20-%20fevrier%20et
%20mars%202012.pdf (Last accessed in December 2019)

[Holy Trinity Tulse Hill on YouTube] “Packing Car Tyre Foundations (Car Tyre Foundations #4)”, [Online] available at: https://www.youtube.com/watch?v=0YV2TG5aypw (Last accessed in December 2019)

[Holy Trinity Tulse Hill on YouTube] “Car Tyre Foundations Plate Test”, [Online] available at: https://www.youtube.com/watch?v=K8Vlz6qNCfU (Last accessed in December 2019)

[König, H., Weissenfeld, P.] “Entretien écologique du bois”, ed. La plage, 2008.

[Lowimpact] “Why cement should never be used with natural buildings”, [Online] available at: https://www.lowimpact.org/why-cement-should-never-be-used-on-straw-bale-houses/ (Last accessed in December 2019).

[Mechanical Concrete] “Award Winning, Economical, Green, Industrial Strength, Construction Technology”, [Online] available at: http://www.mechanicalconcrete.com/ (Last accessed in December 2019]

[Miteco] “Descarbonatac fabrical”, [Online] available at: https://www.miteco.gob.es/es/calidad-y-evaluacion-ambiental/temas/sistema-espanol-de-inventario-sei-/040614-descarbonatac-fabric-cal_tcm30-429852.pdf [Last accessed in December 2019)

[Miteco] “Combust fabricamento”, [Online] available at: https://www.miteco.gob.es/es/calidad-y-evaluacion-ambiental/temas/sistema-espanol-de-inventario-sei-/030311-combust-fabric-cemento_tcm30-430164.pdf (Last accessed in December 2019)

[Naik, Tarun R.] “Sustainability of Concrete Construction”, [Online] available at: https://ascelibrary.org/doi/abs/10.1061/%28ASCE%291084-0680%282008%2913%3A2%2898%29 (Last accessed in December 2019).

[Russian Patents] “Module-type anti-seismic protective unit for buildings and structures”, [Online] available at: https://russianpatents.com/patent/225/2250308.html (Last accessed in December 2019]

[World Green Building Council] “New report: the building and construction sector can reach net zero carbon emissions by 2050”, [Online] available at: ww.worldgbc.org/news-media/WorldGBC-embodied-carbon-report-published (Last accessed in December 2019).

The post Tyre Foundations first appeared on Critical Concrete.

Cooperative housing is discussed in one module of our Sustainable-Sustainable Architecture postgraduate course; if the topics discussed in this article pique your interest, you may be a wonderful candidate. Learn more here.

Introduction

Living in a single-family unit, either in a house or apartment building has become the living standard, but it isn’t the only possibility. Many houses are equipped with appliances and rooms that are used rarely or on a weekly basis, which suggests that there may be a more functional system out there. On the other hand, many houses in urban settings are cramped and unhealthy due to the rising cost of living in cities and urban migration. This inequity is only growing with urban migration patterns and gentrification. 

The single-family housing model is not a viable paradigm for the future. Not only is it an inefficient use of space, but it is also isolating and fails to nurture community. It tends to be cramped for the poor and leaves vulnerable groups to fend for themselves. On a deeper level, these aspects are the exact opposite of what allowed early humans to create society.

Architects, theorists, and dreamers have all wondered how our dwellings can be reshaped for better quality of life and higher affordability, but to solve these issues, they don’t need to strive for the most complicated answer. Two possibilities already exist to challenge the housing paradigm. Housing cooperatives have existed for over a century and challenge the notion of housing as a commodity. Cohousing is a method of living with others to maximize space, resources, and community. These ideas have potential to not only remedy urban housing challenges, but also to home in on environmental sustainability in domestic spaces.

a basic comparison

Cooperative Housing

Housing cooperatives, or co-ops, have existed throughout history, yet in most places they are not recognized as mainstream housing possibilities. In fact, they’ve gone so far under the radar that you might be wondering what in the world a housing cooperative is. Let’s rewind.

A housing cooperative is a housing business which has shared ownership by its residents.[1] The goal of this collective ownership is affordability rather than profit.[2] Aside from collective ownership, there is one feature that is almost always present in coops: democratic processes.[3] Residents get to vote on the major decisions of the cooperative, such as who can replace a former resident, or whether solar panels should be purchased for the building. Other important elements of cooperative housing are commitment to social goals, security in community, decent housing, personal growth, and transparency in management.[4]

The modern history of housing cooperatives in Europe began in the 1800s in Berlin with Victor Aimé Huber’s cooperative dwellings.[5] The practice evolved and expanded, becoming an opportunity for decent affordable housing and as a possibility for people to have more control over their living conditions. 

Kalkbreite Cooperative in Zurich

Differences between Cooperatives

As the practice of founding co-ops spread and grew more prevalent, many differences arose. There are limited-equity coops, often for low and moderate income shareholders, market-value ownership coops, which do not require affordability; rental co-ops which have more secure tenure and have mixed-income tenants; and mutual aid co-ops which are based on solidarity and self help and are usually self-built.[6] Depending on the country and its policies, funding a new housing cooperative could rely on government, banks, or private investors. Cooperatives can be rural or urban, high rise or groups of single family housing.[7] Some co-ops began as ventures to create exclusive and wealthy multi-family housing whereas others were intended to create housing for the poor.

The most pronounced differences between cooperatives comes down to financing and legal constraints, both of which are influenced by the government where a cooperative is located. Cooperatives around the world vary subtly because of governmental constraints in their respective countries, so these are a few examples to show the possibilities.

In Austria, a country with a strong social housing sector, housing cooperatives which are below market-rate are exempt from corporation tax.[8] The government offers subsidies through public housing schemes via low-interest grants or mortgages that cover some of the construction costs.[9] In Egypt, cooperatives are exempt from many taxes, from industry profit taxes to custom taxes and importing fees, some fees including building license fees and publishing fees, and interest of deposits in banks.[10] They receive a 25% discount on state owned land which can be increased to 50%.[11] 

FCH Housing Project in Egypt

Portugal’s government reduces the VAT from 20% to 5% for cooperatives, and they also provide tax exemptions on land acquisitions and subsidize interest rates for cooperatives with low-income target groups.[12] Pakistan has a unique system for cooperative development: the state provides land to cooperatives, but cooperative shareholders are responsible for the construction of their residence on the plot they are assigned.[13] Interestingly enough, in Germany, although housing cooperatives do receive tax relief, they do not receive money from social housing funds; co-ops are not part of social housing there.[14]

The presence of housing cooperatives often hinges on politics. Since cooperatives greatly benefit from the aforementioned subsidies, tax relief, government loans, and other governmental support, proliferation of new co-ops can fluctuate with political changes. Furthermore, governments can incentivise cooperatives through policy, but they can also place limits on the founding of new cooperatives. For instance, Poland banned cooperatives in 1990, a marked difference from the years they had spent becoming mainstream during the socialist regime.[15] On the contrary, Portugal experienced an increase in co-ops after an authoritarian government which opposed the values of cooperatives was replaced.[16] In Pakistan, a corruption scandal from a cooperative paused registration of new housing cooperatives.[17]

Membership practices in cooperatives mean that even in rental cooperatives, residents are less passive inhabitants than in typical multi-family housing. Democratic foundations within cooperatives mean residents vote on management, changes, and governing structures. Each shareholder can have one vote, but in some co-ops the number of votes is equal to the number of shares. Some cooperatives require all decisions to be voted on by everyone, whereas others allow members the option of voting. Whichever way the voting system plays out, members of cooperatives have a stronger sense of ownership and participation, and can motivate one another to create a greener, healthier housing cooperative.

Student Cooperative in California via tsakett on Flickr

Cohousing

Cooperative housing shouldn’t be confused with cohousing, a modern iteration of intentional living developed in Denmark.[18] Cohousing can be implemented within cooperative housing; the two are separate systems which have potential to work together. Cohousing challenges the single family home in favor of sharing space and creating a stronger community.

Although the idea of living with others isn’t new, the term “cohousing” only arose in 1988 after two architects from the United States observed the phenomenon in Denmark, where it had gained traction.[19] Exactly twenty years prior, architect Jan Gudmand-Hoyer had spent several months discussing housing alternatives with a group of friends, developing plans for 12 houses gathered around a common space.[20] Although the project never took form, he published an influential article on the project entitled “The Missing Link between Utopia and the Dated One-Family House” which elicited responses from many families eager to live in such a situation.[21] Another article, “Children Should Have One Hundred Parents” by Bodil Graae, garnered further interest in the concept.[22] After the articles were published, families came together to purchase sites and construct two projects by 1973, which formed the blueprint for cohousing in Denmark.[23]

Rudolph Schindler House in Los Angeles via Lian Chang on Flickr

The ideas are far from new. While Gudmand-Hoyer and Graae were writing these articles, the hippie movement in the sixties was awash with communes and ideas challenging single-family living. But unlike cohousing, many hippie communes were infamous for being financially and socially unsustainable. Additionally, with roots in the early 1900’s, the intentional communities called kibbutz are well known examples shared living from Israel. In California, the Austrian architect Rudolph Schindler built one of the first ever modernist houses, designed for two families to live cooperatively and share one common kitchen.[24] All this is to say that cohousing is not a particularly unique idea, although its less radical stance is possibly what makes it such a viable housing option.

However, what differentiates cohousing from similar ideas like kibbutzim or ecovillages is that cohousing is primarily an architectural design which fosters community alongside a social agreement to live cooperatively. It does not have ideological connotations and can manifest in various ways. Cohousing can be rural or urban, meaning unlike other kinds of intentional communities, it can respond to the global urban influx. Additionally, cohousing may be equipped to handle the challenges of  urban living, such as elder- and childcare along with social isolation. Some cohousing situations share chores in common spaces such as cooking, which tends to free up time for those with busy schedules. 

Spreefeld Berlin Via MitOst on Flickr

Sustainability in Cohousing

Cohousing has some inherent advantages for sustainability. First, dense dwellings groups are more efficient to heat or cool. If the kitchen and living areas are shared, less furniture is needed and kitchen appliances only need to be purchased once for multiple families. By living in close proximity, people can share their skills, which means residents can help each other with tasks like repairing broken items instead of wasting them and buying new things. Additional benefits include purchasing food in bulk, which is better for transportation and uses less packaging. Shared garden spaces mean some food can also be cultivated in a community garden. Having a garden also provides a space to incorporate a compost bin, a challenging feature for typical urban housing.

Cohousing also has the benefit of community learning and social practices, which helps propagate care for the environment and ecological values.[25] By living with many people, there can be less car dependence. Tasks like grocery shopping can be divided and commuting to work can be done with fewer cars.[26] Finally, shared meals can result in lower food waste.[27]

Vauban Cohousing in Freiburg

Housing More Sustainably

There is potential for even more sustainability in cohousing projects. The fact that many cohousing projects are cooperatively owned, purchased before construction is complete, or even designed with input from the future residents is something that allows for even more ecological interventions. If cohousing projects are designed with sustainability in mind, they can be more energy efficient and prioritize passive sustainable strategies. For instance, common areas can incorporate daylighting and efficient ventilation. The design can include a root cellar to store vegetables for long periods in winter without the use of a fridge. Natural materials such as hempcrete, mycelium, cork, rammed earth and many more could all be used as building materials. Since some cohousing projects include aspects of self-building or auto-construction, materials and techniques are employed with easy repairability and designs that factor in longevity. Some features of sustainable design, like solar panels, come at a premium, but if a project is cooperatively owned, these additional costs are spread out among all the owners.

Occupant ownership via the housing cooperative model also means that there can be experimental sustainable practices that wouldn’t usually be possible in conventional multi-family housing. A garden could be designed to have a phytodepuration wastewater treatment system, which would simultaneously provide a beautiful marsh landscape in the common area. There could be compost toilets, green roofs, or food forests, too. With an ecological group of residents, there is also potential for the use and maintenance of a biodigester to produce biogas for cooking. The possibilities are endless, especially with lots of community minded people with various skills willing to contribute to communal projects.

Conclusion

Cohousing and cooperatives are two approaches to financial and ecological housing issues. They provide a peek into what housing would look like if we didn’t approach it from a single-family perspective. When the concepts are combined, they create feasible models for better living conditions, affordable housing, and stronger communities. Moving away from profit and towards collective action gives an added opportunity for a more ecological way of living. Existing cohousing cooperatives are great launch pads for pushing the possibilities of environmentally sustainable multi-family housing, while budding cohousing cooperatives have the opportunity to design healthy living spaces for both people and the planet. 

[1] https://4bfebv17goxj464grl4a02gz-wpengine.netdna-ssl.com/wp-content/uploads/drupal/Profiles%20of%20a%20movement%20final%20web%20ISBN.pdf

[2] Note: There are some cooperatives which are not intended to be affordable housing, but the collective ownership does improve the affordability, even in those cases.

[3] https://www.ica.coop/en/events/cooperative-housing-key-model-sustainable-housing-europe

[4]https://4bfebv17goxj464grl4a02gz-wpengine.netdna-ssl.com/wp-content/uploads/drupal/Profiles%20of%20a%20movement%20final%20web%20ISBN.pdf

[5] https://www.housingeurope.eu/event-183/cooperative-housing

[6] https://www.housinginternational.coop/sdgs-2/cooperative-housing-models/

[7] https://4bfebv17goxj464grl4a02gz-wpengine.netdna-ssl.com/wp-content/uploads/drupal/Profiles%20of%20a%20movement%20final%20web%20ISBN.pdf

[8] https://4bfebv17goxj464grl4a02gz-wpengine.netdna-ssl.com/wp-content/uploads/drupal/Profiles%20of%20a%20movement%20final%20web%20ISBN.pdf

[9] Ibid.

[10] Ibid.

[11] Ibid.

[12] Ibid.

[13] Ibid.

[14] Ibid.

[15] Ibid.

[16] Ibid.

[17] Ibid.

[18]  https://www.cohousing.ca/about-cohousing/history-of-cohousing/

[19] http://www.cohousingco.com/cohousing

[20] https://www.cohousing.ca/about-cohousing/history-of-cohousing/

[21] Ibid.

[22] Ibid.

[23] Ibid.

[24] https://www.archdaily.com/783384/ad-classics-kings-road-house-rudolf-schindler

[25] https://www.iberdrola.com/social-commitment/cohousing

[26]  https://www.moneycrashers.com/communal-living-cohousing-types-benefits-intentional-communities/

[27]  https://www.moneycrashers.com/communal-living-cohousing-types-benefits-intentional-communities/

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