Let’s compare two different house designs in light of economy: a dome and a typical Panamanian block house. First, the 30 foot diameter, four-frequency (each triangle of the basic icosahedron is divided into four levels consisting of 16 interior triangles), three-quarter sphere dome: Using The Dome Book to calculate lengths, fabricate the 360 or so framing struts, which are 2½’ to 4′ long. They could be cut from about 1000′ of metal 2″x2″ framing joists, or could be fashioned from metal pieces (such as aluminum channel) salvaged from a scrap yard. If hubs are used, fabricate these also. Nuts and bolts you must purchase new (cheaper in the Free Zone!). Assemble the struts into a dome superstructure consisting of 240 triangles, wrap this frame with a layer of burlap and paint or spray this burlap skin with a thin slurry of cement, thus creating a surprisingly strong, light shell, like an egg. This idea is adapted from a similar one in Ken Kern’s Owner-built Home.
As you can imagine, cement would be a very minor expense for a dome surface area of around 2000 sq. ft. (after subtracting for door and windows). You could build this shell for $1300, before plastering. Assume that the conventional concrete foundation and sub-floor, plus plumbing, would be the same for both houses (cost not yet included). But there is a way to radically reduce cement usage here also, using the same burlap reinforcement technique for the floor. Combine this sub-floor with ten concrete piers as a foundation around the perimeter of the dome. Doing the floor/foundation this way could add as little as $200 to the cost, for a total of $1500 (assuming 2005 Panamanian prices).
A conventional Panamanian concrete block house with the same floor space as the dome would measure 37′x 37′ and be 8′ high inside. Using 4″ wide (half-size) concrete blocks for outside walls and a central bearing-wall would cost $450, or 30¢ X 1500 blocks (after subtracting for doors and windows). Add mortar for $300 for a total of $750, including delivery. Labor would cost $750, or $25/day for a mason and helper for 30 days (pre-paid, they could do it in ten, but I’d be suspicious of the quality of the work). The roof would measure 46′x46′, about 2000 sq. ft. Metal roof beams and framing would cost the most and I am guessing from just one report that it would cost $3000 for materials and labor. Add corrugated galvanized metal roofing for $1000, including labor; finish with a simple drop-ceiling for $500, including labor.
There you have it, an unplastered block house, without rooms, such as can be seen scattered all over the suburban and rural landscapes. Cost: $6000 or around $4./sq.ft. Concrete foundation and floor plus plumbing are not yet included but in actuality must be completed first, so double the cost. This $12,000 figure would amount to two years’ earnings for a working class family. For rural peasants it’s more like 4-6 years’ earnings. In reality, most houses are only 1/3 to 1/6 of this size. Since there is no financing for most locals, it’s pay as you go, so it could take years to get this far on such a project. If you are way up on a mountain, far from the sources, then delivery costs could add a lot more to the cost of these materials, mostly because concrete is so very heavy.
I just got some figures for a friend’s finished concrete block house: $12 per square foot if you act as your own contractor and hire the craftsmen and laborers you need. The biggest expense by far is framing and pouring the steel-reinforced concrete foundations and floors, followed by roof materials. This $12 figure includes wiring, plumbing, septic system, finishing the outside and inside surfaces, plus doors, windows and fixtures The owner did some of these jobs himself. USA costs are eight to ten times that figure.
Did you ever build any domes in Panama?