Earth has been used as a building material for thousands of years; Today, one third of human population resides in earthen houses. Earth is the most important natural building material and it’s available in most regions.
Newly developed, advanced earth building techniques demonstrate the value of earth not only in DIY building, but also for industrialised construction involving contractors.
Prejudices against earth as a building material
Owing to ignorance, prejudices are still widespread. Many people have difficulty conceiving that a natural building material such as earth need not be processed and that, in many cases, the excavation of the foundations provides a material that can be used directly in building.
The anxiety that mice or insects might live in earth walls is unfounded when these walls are SOLID. Insects can survive only provided there are gaps or cracks.
Also, insects can appear if the earth contains too many organic additives, as straw, with a density of less than 600 kg/m3.
About cleaning them, people may think they are hard to clean, but loam surfaces can be protected with paint that help its cleaning (the paint makes them non-abrasive), using additives as casein, lime-casein, linseed oil and other coatings.
Ironically, bathrooms with earth walls are more hygienic that those with glazed tiles, since earth absorbs high humidity quickly, thereby inhibiting fungus growth (another example that our perception could have been influenced by marketing or media promoting industrialised building materials … they “look” cleaner than earth, but they are not)
Having said that, loam has real “pros” and “cons” when compared with industrialised building materials.
Let’s start with the cons, bad news first
1 – Earth doesn’t withstand water, it’s not water proof
Loam must be sheltered against rain and frost, especially in its wet state. Earth walls can be protected by roof overhangs (eaves), damp proof courses, appropriate surface coatings, etc.
For mud plaster that is exposed to rain, it may need stabilisers (cement, lime, animal products, bitumen, soda waterglass, plant juices like oil and latex, etc.)
|Waterproofed earth wall in sink and shower area||Exterior surface protection like lime paint|
|Eaves (good hat)
Usually 1 m. minimum
|(1)||Stem walls (good boots)
Usually 20 – 50 cm.
2 – Earth is not a standard building material
Depending on the site where the loam (a mix of clay, silt, sand and larger rocks) is dug out, it will be composed of differing amounts and types of clay, silt, sand and rocks.
Its characteristics therefore, may differ from site to site, and the preparation of the correct mix will require some research on site, and the possible need to apply additives to get the mix you need.
3 – Loam mixtures shrink when drying
Due to evaporation of the water used to prepare the mixture (water is required to activate its binding strength and to achieve workability) shrinkage cracks will occur.
The linear shrinkage ratio is usually between 3% and 12% with wet mixtures (such as those used for mortar and mud bricks), and between 0.4% and 2% with drier mixtures (Rammed earth, compressed soil blocks).
Shrinkage can be minimized by reducing the clay or water content, optimizing the grain size distribution, and by using additives (thinning with more sand or larger aggregates, adding fibres as straw) or methods (shrinkage joints, reduce loam components distance/size, enhance drying time)
Now the pros!
1 – Earth is completely reusable, has minimal embodied energy and is usually highly available at a very low cost
Loam is always reusable, can be recycled and indefinite number of times over a long period, at a very low recycling energy cost (just break it down and add water). It NEVER becomes a waste material that harms the environment.
2 – Earth is safe and harmless to your skin, lungs and eyes (most industrial building materials are the opposite)
3 – Earth regulates humidity inside the building
Loam is able to absorb and desorb humidity faster and to a greater extent than any other building material, enabling it to balance indoor climate.
If we take into account that in moderate and cold climates people spend 90% of their time in enclosed spaces, indoor climate becomes a crucial factor in wellbeing.
Humidity of less that 40% and higher than 70% can cause many health problems.
4 – Loam stores heat
Using loam, helps with thermal balance, is ideal for passive solar design heat storing and could be also used as heat storage in a rocket stove mass heater system.
5 – Loam is ideal for do-it-yourself projects (and communal work)
Provided the building process is supervised by an experienced individual, earth construction techniques can be executed by non-professionals. Since the processes involved are labour-intensive and require only inexpensive tools and machines, they are ideal for DIY.
6 – Loam preservers timber and other organic materials
Due to its low equilibrium moisture content, and its high capillarity, loam conserves the timber elements that remain in contact with it keeping them DRY.
Normally fungi and insects will not damage that wood as they need 14% to 18% humidity to maintain life. Similarly, loam can preserve SMALL quantities of straw that are mixed into it.
7 – Loam absorbs pollutants
Is often maintained that earth walls help to clean polluted air, but this has yet to be proven scientifically.
But, it is a fact, that earth walls can absorb pollutants DISSOLVED in water (e.g. sewage treatment).
Want to learn how to use earth to build a home? Come and join us to our next Natural Building Course, it will be highly oriented to Light Earth building, hurry! not many places left!
Note: Content extracted and adapted from “Building With Earth – Gernot Minke – 2012”
References and acknowledgements:
(1) Picture taken from hummingbirdcommunity.org