Dr. Joe Lstiburek Discusses How to Insulate Foundations and Protect Exposed Exterior Foam
rockies63
| Posted in General Questions on
A lot of people wonder about how to protect the exposed exterior foam on their foundation wall (between the surface of the soil and the first floor framing).
Other have questions about insulating slab on grade foundations and crawlspaces. This article has some practical solutions.
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Search and download construction details
Replies
Well that's funny.
I just posted that my GC tarred my foundation 100% and I couldn't find a product solution to make this black look like paraging. The creative solution recommended here was aluminum to cover up the tar. This is his solution for protecting the foundation.
I take issue with his authority that some, not all fiber cement board makers are against ground contact. In fact, all US fiber cement board makers are against ground contact, except for one company in the US and they only sell through themselves...So they either that one company that advertises as the only ground contact rated cement board maker in the US knows magic that Hardie and USG don't know...or...
I used that shiny pebble grain fiberglass sheet you see in industrial kitchens and public bathrooms.....only backwards so the dull side faces out. Available in gray at The Despot. Like 5 years plus and so far so good. Caveat: house is surrounded by gravel so no weed whacking or lawn mower wheels running into it, no driveway next to it or any other reason it would get beat up. Adhesives and the weight of soil are holding it on, so a couple places it has slipped down, so I need to fix that. Probably should have driven some anchors below ground level.
The design of my house is such that the foundation is deliberately proud of the walls, but on a 'normal' house you would probably not notice it was not concrete if your attention was not drawn to the seams.
When we built ours I had a stainless flashing bent that went under the exterior stud wall and 12" down the foam on the outside to protect it. and then backfilled up to that. It's caulked to the concrete and caulked to the sill seal. It does double duty protecting the foam and as a termite barrier. Little spendy but it worked well and should last for years.
For an ICF wall on a slab on grade construction. For below grade, I've seen them use synthetic stucco on the outside ICF wall all the way down to the footing. The synthetic stucco protects the ICF EPS foam and it is also waterproof so it also provides a moisture barrier. For termites, I would also recommend a termite treatment in the soil around the perimeter of the foundation. They last around 15 years and can be retreated if needed.