Our earthbag design team is busy creating home and shelter designs, as well as innovative building ideas for the reconstruction effort in Haiti. (See Kelly Hart’s Alternative Bond Beam and Lintel system, for one example.)
As you’re probably aware, conventional bond beams and foundations are made with reinforced concrete, but these are costly, labor intensive and the materials are particularly difficult to come by in Haiti since the earthquake. They also rank low on the scale for sustainability. What’s needed is a way to stiffen earthbag walls and create bond beams using more readily available and affordable materials.
This particular building detail was sparked by a discussion between Patti Stouter, her husband and I.
One option is to use corrugated metal and wood strapped together with earthbags. Corrugated metal is used widely throughout Haiti and most other countries, and is fairly ease to work with. Wood is scarce, but it can be salvaged from damaged buildings. Hopefully more of these supplies will arrive shortly.
If corrugated metal cannot twist, it is very strong at resisting pressure across the corrugations. Tightly sandwiched between layers of earthbags, it won’t be able to twist. It can keep a long straight wall from bowing out. Overlap ends about 12” and pin it well at corners and it can keep the walls from moving apart during a quake.
This kind of brace may be very helpful low in a building instead of a concrete foundation. It can be used higher in the wall for added strength, and possibly save money and labor by not building posts or buttresses.
In the same way, this type of sandwiched metal can be used for a bond beam. Because its strength is greatest if it cannot twist, it must be securely fastened between earthbags. Strong ties are an important part of this structural system. These must be protected from sun and moisture by being encased in a layer of plaster.
A corrugated metal bond beam and braces can be dismantled and reused if an emergency shelter is rebuilt or expanded. For instance, wall heights can be raised, and the materials reused without great difficulty.
One thing your forgetting is the incredible strength of bamboo. Call Earth advocates research center/farm and talk to Adam. He will teach you about building with bamboo and how it has been successfully used to replace rebar in engineering tests with concrete and other building methods. Thanks.
Jeff
We know about bamboo. Trouble is, there’s very little available in Haiti from what we’ve heard. Also, it would be very difficult if not impossible to drive it down through the bags as we’re planning. External pinning with bamboo lined up on opposites sides of walls and tied together through the wall is one possibility.