Above is a recent photo of a house in Belize that we rented for a few months back in 1983. This house is around 40 years old, and is still in good shape. It sits on a concrete slab, but the house itself contains no concrete and no lumber. (The only wood products used are a few light pieces of trim around the windows and doors.) The house is made of light-weight metal studs, some of which you can see protruding from the gable end on the left side. The roof is metal, the outside walls are thin cement-based composite board with an even thinner coating of stucco. The inside walls are gypsum drywall. The total package is strong, light, waterproof, and wind- and fire-resistant.
The situation in Haiti: hundreds of thousands of people are now homeless. The UN has decided, wisely, that providing tents for these people is a waste of money. Instead they're trying to provide them with metal roofing to construct makeshift shelters. Ultimately the answer may be structures like the one pictured above. A metal roof supported by a metal framework would provide durable shelter from the rains which will be starting by June, and would also be light enough not to present a threat in the event of another earthquake.
As long as the walls were firmly anchored, the floor could be an afterthought, installed later when the owner had enough time and resources to do so. Even the walls could be temporary, eventually replaced by a lath or hardboard covered by a type of tabby.
Given a workable design and a few basic materials, coupled with the average Haitian's ingenuity in scrounging scrap materials, which should be available in abundance, there's a chance that this type of construction might be the answer to Haiti's need for permanent, safe housing. Just a thought....