Protecting ICFs between grade and siding; parging etc
I should have sorted this out a long time ago, like before backfilling my foundations I guess, but never mind.
I have ICF foundation walls up to the subfloor level. I have a cedar band with the bottom roughly at subfloor level and then hardipanel above that. The ICFs are protected below grade with dimple-sheet and blueskin to cover the top of the sheet. Actually, due to some ‘misunderstandings’ the blueskin and occasionally even the dimple sheet go above grade. At the front of the house (the walkout basement part) the blueskin goes right up under the hardipanel.
I’m having trouble deciding what to do to protect the ICFs between grade and cedar band, and assorted googling hasn’t really found anything too exciting so far. Parging cement seems to be the default but I’m not sure I see it sticking to the blueskin too well, so maybe there is a problem there. I’ve seen strips of concrete board suggested, which might work I guess but surely I’d still have to use parging etc to seal the gaps; at least it should stick to concrete board! Someone posted a suggestion to use roll stock Al or even copper($$$) but that seems like it would be prone to dents and creases. Perhaps it could be cut and bent on a brake to make a built in drip-edge.
Something that concerns me about any of the sheet/board suggestions is the possibility of ants/termites/alien slugs with laser gun eyes crawling up behind it and not being detectable until too late.
Suggestions would be welcomed; low cost ones especially. You know how it is I’m sure – at the end of the building process you tend not to have a lot of money left over…
There’s a bunch of pictures that might illustrate my issue at www.rowledge.org/tim/building both in the progress slideshow and the blog pages.
Replies
Nearly a year later I'm back to having to think about this (small matters like floors and kitchens and deceased relatives delayed things a touch) and hoping someone has some experience to share
I'd peel down any waterproofing materials to grade level and use synthetic stucco to cover the exposed foam. Waterproofing is just not needed above grade.
I've been around a few dozen ICF houses and synthetic stucco is really what I see as the best bang for the buck since it's quick to apply and the foam surface is a perfect base. The products I'm familar with involve a thin coat (1/16"ish) followed by working a fiberglass mesh into that coat. When dry a second thin coat (1/16"ish) is troweled over that and you're done.
I've had tgraditional stucco guys try to justifiy simply using a lot of moose milk in a thin skim of stucco - and I've never seen that done in a way that doesn't crack and look like crap over time.
Hardiplank down to grade looks funny to me - same for metal flashing of any kind.
There are probably other products that can adhear to foam and provide a uniform surface that will resist cracking such as elastomeric paint, but joints in the foam block will telegraph through, which is why a troweled on product is ideal.
The only other option that I see as being a good idea is stone - either fake or real - and only if it helps the design of the house. It's much more expensive than synthetic stucco and is more involved to install.
Thanks Don,
about the synthetic stone thing - I was under theimpression that it wasn't supposed to go down to grade? I'd love to use it and it might even be affordable since there is just 250sqft to cover.
I could just about get away with 'fixing' the over-height waterproofing in some ares but there are places where it would be a nightmare job. I'm thinking maybe screwing metal lathing mesh to the ICF tabs in these areas.
It shouldn't go completely down to grade - if it does it will wick moisture from the ground, but stopping a few inches short still gives the same good look.
That's the same reason I don't care for the idea of running hardi backer down to grade - it will wick water.
The synthetic stucco I've used reminds me a lot of an exterior caulking mixed with granular material for the texture - it doesn't breath or allow moisture to wick - perfect over foam - but you don't want to use metal lath with this stuff - it goes on in very thin coats.
Pulling waterproofing membrane off of foam isn't normally all that hard above grade - normally it seems to fall off on it's own where backfill or something else doesn't keep pressure on it, but on a hot day or with a little help from a heat gun it normally comes off easily like an ice and water shield would.
Stuco light
As Don say synthetic stucco is the norm over ICF. Ussualy it is a ready mixed material you can purchase.
I used an idea from another guy that use to be on this site, but now is over at BTC. I call it stucco lite.
Just screw DuraRock to the ICF foam tabs. Then tape the seams and do a light scratch coat of regular stucco , followed by a finish coat with your choice of texture. The cement backer board provides a tougher base over the ICF foam than the synthetic stucco products. It is far less likely to be damaged by weed eaters, lawn mowers and other yard tools. Even with the cement board it still comes out a little cheaper than a properly installed synthetic stucco.
Thanks Dave,
I can see concrete board working pretty well so long as I get a type that is actually ok for below grade. Best not to use that left-over drywall I guess :-) Enough Durock to do the job would be a couple of hundred $, so not a lot.
Below?
No need to run it any lower than your finish grade. Maybe a couple of inches and that is all. DuraRock is tuff stuff. That is why it is use in wet loactions behind tile. Exterior exposure with a parge coat over it will last longer than the foam underneath it.
DW is making glass mosaic panels on durarock for our porch band boards and panels for the "baluster" in between the rails. Thinset, durarok, and glass all exposed to whatever mother nature send our way.
You can solve this technical problem on discussion with engineer or any expert in construction industry...
....hmm....where could we find these "construction experts" that make a living installing ICF foundations and doing these kinds of things?....hmmm..... :)
If only there were a good place to ask the pro's... I know, how about we set up one of them website-thingies and trry some of that new-fangled "social networking" stuff?
So I was wondering the same thing. Can you parge over blue skin/ how to parge over blue skin? Since no one actually has an answer on the internet anywhere I decided to make an account to share my experience and how to do it. You can parge over blue skin by using galvanized lath small tapcoms with fender washers or concrete screws to secure the lath the foundation. Then parge over top of the lath.
You're all welcome and good luck