We have yet to try it on a full-scale dome project, but we've collected loads of free asphalt shingles and hammered them into the mud-plastered surface of the Honey House dome. They are easy to anchor, and stagger to conform to the curve of the roof. They can be installed very thickly with an overlap of one inch (2.5 cm) or less creating a thick, thatched appearance. Earthbag domes can carry a substantial load. With shingles set this thick they could last a lifetime, and we may have developed safe and effective ways to recycle them by the time they need to be replaced.
Since asphalt shingles do not breathe, a cupola might be in order. This may be built in such a way that any moisture vapor that builds up under the shingles can travel upward, perhaps along channels sculpted into a base coat of earthen plaster, and vent out the cupola. The eaves can be extended to rest on a wrap-around portico of earthbag arches or a post and beam porch.
Wood shakes and shingles are a natural, breathable alternative to asphalt or fiberglass shingles, and can be applied directly over well-executed bag work without any base coat of plaster. In essence, any kind of roof tile from slate to terra cotta to slab stone can be easily supported by a properly constructed earthbag dome. Experiment, explore, heighten, and discover! (Fig. 13.8).
13.8: Shingles applied directly over an earthbag dome with built-in extended eaves to protect walls.
168 EARTHBAG BUILDING
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