Nothing can be simpler than mud. It’s been around forever and can be found everywhere on the globe. In fact adobe bricks, which are essentially sun dried blocks stacked and cemented together with mortar, are then either left alone or covered over with an earthen plaster (so that’s mud to the power of three). Adobe huts have been around 5000-6000 B.C. in areas such as Egypt and Iraq. Obviously the common denominator here is a dry, hot geography essential to air drying the bricks, although mud has come a long way and is in use all over the world. Originally perceived as a poor man’s home the concept has evolved to include gorgeous monasteries, mosques and residences.
Perhaps the most obvious vulnerability of this building material is its lack of resistance to water. In arid parts of the world this may not be a problem, but for those of us who like April showers because they bring May flowers…it is. Waterproofing adobe walls from streams of water, free standing water or seepage from underground becomes imperative no matter which foundation you ultimately go with, although here in the western world poured concrete is generally the one of choice.
Adobe bricks can be made to whatever size you want them to be bearing in mind one thing…are you planning to hire a crew or DIY? If you make them huge (10x14x4 inches and 35 lbs) you better have body builders as friends because you aren’t hefting a single brick, you are handling thousands to build a structure, and this limits who can get involved.
Adobe bricks are made from mud containing a ratio of approx. 20% clay and 80% sand, although building codes in your area may require a higher percentage of clay as it acts as the binder. Of course getting the ratio right is important in that too little clay and you’ve got cracking whereas too much sand and the bricks become brittle and less resistant to weathering. If the big bad wolf can blow the mud house down then what would be the point? There is a way of testing your subsoil to see if it is suitable for making your own bricks (refer to Steve Berlant’s book-Vol.1 The Natural Builder for details) or you can simply purchase the soil from a local supplier. You can start using air dried bricks after about two weeks although they don’t reach full strength for a month under optimal conditions. You know when a brick is dried all the way through by breaking it in half and seeing if the color is uniform throughout.
There are many variations on how to make adobe bricks. Some people add chopped straw as it creates a lighter brick to handle. Others use an asphalt emulsion (oil by-product) which makes them water proof. However this contains some serious chemicals that smell and are potentially harmful which are seen by many as unnecessary when outside walls can be plastered to protect from moisture instead. Some people further south (Mexico) fire the bricks in a kiln for two days which makes them harder than the air dried variety, but they also absorb more moisture which can accumulate inside the brick and flake during contraction and expansion. Pressed earth blocks made by machines (with a little cement added) may lack the charm of individual hand made bricks, but on the practical side they can compress a really strong block, of a consistent size, for use almost instantly in both wet and colder climates.
Of course no matter which blocks you use they will need to be ‘cemented’ together with an earthen mortar made from the same mud as the bricks minus the little stones and organic matter. Did you know it is an old Persian custom to toss some coins into the mortar for workers to find so they will sift through all the mortar more thoroughly?! Personally I think that was a sign that they should have asked for a bloody raise.
Here’s a weird little variation on adobe building called ceramic houses. They are made of adobe bricks and mortar as well, however after the house is built the whole thing is fired like a kiln using a gas heater in effect baking the place from the inside out. Clever eh?
To protect the walls from weathering, the final stage of any adobe project is plastering. Earth plasters resemble mortar except they have more clay, and since wind and rain will wear it down it becomes an annual ritual to check for cracks and do maintenance. Lime plasters on the other hand are far more resistant to weather although if the idea of making maintenance an annual tradition turns you off you can always apply a sealant of your choice. Cement stucco may seem like a good idea on the surface, however, as with most organic structures it restricts the walls ability to ‘breath’, thus moisture gets trapped inside damaging your home even in dry climates. Check out Steve Berlants’ book – ‘The Natural Builder’ Vol. 3: Earth and Mineral Plasters for more on that.
For those of us in the Great White North (colder climates) installing rigid foam insulation to the outside wall to isolate the thermal mass from the environment is recommended. The foam is then covered with felt paper, chicken wire, and stucco. Of course you could also opt out to build a double wall with a space in between which is then filled with insulation…but that feels like doing twice the work to me. Here’s the thing. Adobe on its own doesn’t have much in the way of insulation, however, depending on where you live it does have great thermal mass properties. If you are losing too much heat through the walls, build thicker walls. So what about adobe? Good, bad, or ugly in large part depends on where you live.
Advantages of Adobe:
- Widely available building material that could provide housing for many, especially in third world nations
- Adobe has been around forever. Building codes exist for it.
- Adobe walls are fireproof. In fact fire hardens it.
- Adobe can be used to build a variety of styles/designs.
- Adobe can be re-cycled. Broken bricks can be wetted and repaired, and intact bricks from demolitions can be re-used.
- Adobe is a good sound insulator so expect a quiet night sleep.
- Adobe buildings stay warm in winter and cool in summer in arid dry climates with cool nights
- Adobe’s thermal properties make it awesome for homes heated via passive solar energy
- Local manufacturers of mud bricks = local economy
- Minimum skill is involved for making adobe bricks. Perfect for the DIY
- If made on-site or nearby, adobe bricks have low embodied energy
- No pollution
- Bricks can be made by hand, by machine or can be purchased.
Disadvantages of Adobe:
- The perception of poverty surrounding this abundant building material which could house millions, but due to the love affair with Western culture and its modern techniques is being abandoned.
- Making bricks and building walls is labor intensive and costly if you hire out
- This construction is straight up hard work.
- Traditional adobe brick making can only be done in dry/hot climates, not cold/humid areas.
- Bugs and Critters can burrow through the walls (although plaster reduces this)
The Natural Builder, Vol.1, 2, & 3 by Steve Berlant
The Adobe Story- Paul McHenry
Adobe: Build it yourself- Paul Graham McHenry Jr.
Ceramic Houses and Earth Architecture by Nader Khalili (1996)
YouTube offering: http://www.youtube.com/watch?v=qCEdDM-c7RQ&feature=fvw
Adobe/Rammed Earth Builders and Associations:
Image Credits: Tricia Simpson, Wikimedia, Kevstan, Soare, neil cummings, Proyectohornero, Friedrich Kircher