The rain this year seems endless. A constant barrage on the building envelope, in the form of pounding rain, waterlogged soil, or evaporating moisture when (and if) the sun finally comes out. And then my thoughts turn to capillary breaks…
Is this the first step to a heart attack? No? Then why does there seem to be so much resistance to adopting this concept? Really, it is simple. The ground can hold moisture. Most building materials used in exterior walls can wick moisture. Buildings shouldn’t have moisture in their exterior walls – especially when the material is susceptible to things like rot or mold. So what do you do? Wood framing practices is to break the pattern of wicking with a non-permeable material - like a sill seal foam gasket. New concept? Not really. Look at these photos – one from Switzerland and the other from the mountains of North Carolina. My guess is they didn’t trade e-mails over 100 years ago to compare notes – but both figured out a solution against rising damp.
And what if the building material does NOT rot – like stone or concrete? The water still wicks up, and then it moves from wet to dry. This moisture could then collect on the paper backside of sheetrock, or into some wood work, or evaporate into the air (indoor or outdoor). And, like a science experiment – this wall will continue to wick up water and evaporate it into the driest medium. We may not hear as much about these problems, because the concrete itself won’t rot, and there may be a few cases where the path of the moisture won’t cause damage. But the problems may surface elsewhere and get blamed on the HVAC: excess moisture leading to carpet mold, swollen wood trim, wallpaper peeling.
What is the solution? Slab foundations should be disconnected from ground water in any case. For footings, slather on a waterproof coating before your place the stemwall/ basement wall. Anything with an acrylic component, or a rubberized membrane.
Prevent liability which may lead to heart-attacks – go for the capillary break.
Petit, Betsy. RR# 0509b Details for Avoidance of Mold—Foundations. www.buildingscience.com