Posted By galore on 06 Jun 2011 10:38 PM
While I realize that the styrofoam isn't 100% waterproof, it is almost waterproof. At least my cheap styrofoam cooler doesn't leak and styrofoam cups work well for coffee without leaking...
I agree. Before I built my house I took a portion of a Buildblock form and submerged it in water for 10 days to 2 weeks, as I recall. It increased no measurable amount in weight, using a 5 lb postage scale with a preciseness of 1/10 oz or 1 gram. On the other hand, I have seen floating boat docks settle lower and lower in the water over several years as the styro blocks underneath got waterlogged. Also, my brother's hot tub cover got water logged after about 10 years of use.
The extent you go to to assure no water gets into the ICF blocks depends in large part how severe the water presence will be against the block. I think a drain pipe on both sides of the footer, plus providing a clear pathway for water to drop down to it, is the best approach except for maybe the most extreme conditions.