01-15-2009, 04:10 AM
Our goal was to construct a house that is pretty much impervious to the Puna climate. Our house walls are single wall, contructed of ProTec SIP panels (distributed by Rob, www.castleblock.com) which are cement board panels sandwiching about four inches of styrofoam. They are 3'x9' and set vertically and joined with galvalume splines. For finish we were able to work with them exactly like sheetrock which made it relatively easy for us amateurs on both the exterior and interior. On both sides the vertical panel's edges were bridged with webbing identically to regular sheetrocking. For the exterior the webbing was a strong plastic (from Honsador) about 4 1/2" wide attached to the cement board with a rubbery substance used to seal concrete shower pans. Then we applied Thinset rather than typical stucco (which does not stick well to the smooth cement board) directly to the panels. The sticky Thinset was trowelled on identically to wallboard compound with which we already had some experience. We used two coats, the first a relatively inexpensive, sandy type and the second layer a high end, very fine-grained and smooth product. In our climate we avoid texturing surfaces as much as possible to reduce dust capture and mold. Finally, at Home Depot, we found a one coat stucco paint with a very thick texture that we rolled and brushed on. It really turned out to be one coat. The exterior took the two of us several weeks of part time work, but a crew should be able to accomplish this in a few days.