There’s obviously a great deal of concern about the recent earthquake in Haiti. Disasters like this are all too common, and so we’re working hard to develop at least two low cost, easy to build earthquake-resistant earthbag house designs.
We hope to be better prepared in the future with plans ‘ready to go.’ But in the meantime, we are making good progress. Kelly Hart and I have roughed out some basic design details. Adobe engineer Bill Druc has offered to help with the calculations and designer Patti Stouter has offered to do some drawings. Also, numerous organizations have expressed interest in raising donations, sending building materials and trainers, and constructing houses in Haiti. For the latest news, see Comments at Responding to Catastrophe.
Earthbag buildings tend to flex and distort during an earthquake rather than suddenly collapse as wood framed, adobe, brick and concrete block structures do. Barbed wire and plaster mesh hold the bags together in case of collapse, thus greatly reducing risk of people getting crushed.
Key building details for earthquake-resistant earthbag houses in Haiti:
– Use compact shapes for greater seismic resistance: round, curved, hexagonal, octagonal shapes or domes when culturally appropriate.
– Avoid long unsupported walls.
– Foundation: gravel-filled earthbag foundation (double-bagged for strength) on rubble trench. Best to have at least two continuous courses of earthbags below door threshold.
– Barbed wire: two strands of 4-point barbed wire between courses
– Limit the size and number of doors and windows: these may be available from collapsed buildings or acquired locally to save shipping space. No glass in windows, only shutters that can be locked. Concrete breeze block or screened openings can reduce number of windows required.
– Steel-reinforced concrete bond beam: 6” high x 16” wide
– Truss anchors in the bond beam: embed L shaped rebar anchors or truss anchors at 24″ on center and weld or bolt to rafters/trusses
– Lightweight roof: about 3:12 pitch, metal roofing for roofwater catchment
– Plaster mesh: poly fishnet is the lowest cost, won’t rust and can easily be stuffed into barrels full of building materials. (Barrels are later used for roofwater collection.) Add fishnet to both sides of earthbag walls and connect with poly twine.
– Plaster: cement or lime plaster on exterior; earth plaster on interior
Virtually no structure can withstand a direct hit from a major earthquake, but by combining the building details listed above there is a very good chance the structure will hold together even if the walls should topple. While not perfect, this strategy could save countless lives over the current building methods used in Haiti.