Replies

1. GBA Editor
   MIKE GUERTIN | Dec 21, 2009 10:45am | #1

   Capillary action of earth moisture takes place in every climate zone. The only case I can think of where capillary action would not take place is on homes with footings to permafrost.

   The slides were Pete's so he can comment on the specific location / climate zone. I would guess it was a northern climate zone 5 or 6. I've encountered wicking problems through concrete slabs in southern zones. Though slab-on-grade homes are a less likely to have wicking problems than below-grade slabs (basements, crawlspaces), the potential exists whenever there isn't a capillary break - either a space (think crushed stone) or barrier (plastic).

2. 
   Riversong | Dec 21, 2009 01:32pm | #2

   I didn't see whatever slide show you're refering to but, in addition to the permafrost example, a concrete foundation in a desert is unlikely to experience wicking problems.

   The theoretical vertical limit to concrete capillarity is 6 miles! A concrete slab or foundation must be isolated from ground moisture. Almost no builders bother to place a capillary break between a footing and a foundation wall, all but guaranteeing wicking into the wall even if it's well-sealed on the outside.

3. 
   Peter Yost | Dec 21, 2009 09:20pm | #3

   The slides on capillary breaks were from Atlanta.

   Deserts? One of my students in an online course with Boston Architectural College was from a Mideast country where even when they build in the desert, they can have problems with ground moisture and wicking. Surprised the heck out of me, but because capillary breaks are so hard to retrofit and so easy and inexpensive to do in the first place, err on including them.