I am about to build an ICF house on an island north of Scotland and wind driven rain is a major issue here. I am wondering whether to do the whole pour with waterproof / watertight concrete. Other than cost, can anybody see any disadvantages with this approach? The house will be covered with a waterproof render (stucco?) but I want to be extra sure that I don't have damp walls. The house will be fitted with a heat recovery ventilation system so there should be plenty of air moving through it. Thanks for your help. AA

i am an icf distributor/builder/rep in florida, living in an icf house with insuldeck concrete roofs and regular painted cementicious stucco on all walls.
we have been through several hurricanes and seasonal "horizontal rain" thunderstorms.
no leaks or moisture through the walls. regular 3000 psi concrete in the walls and on all roof surfaces, which, by the way are not yet sealed and some even have the usual hairline cracks.

we also have a 35 year old 5 story icf condo (no roof overhangs at all) in daytona beach, on the ocean, which was build and finished the same way described below, without any moisture problems.

to me the most important prevention of leaks is the caulking and painting of the transition of windows and doors with the walls. my windows are inset halfway into the opening and mounted directly to the concrete about halfway in the opening, with stainless steel tap-con screws (i'm on the ocean... suggest you dont use anything but stainless there!!!). the stucco is wrapped around and into the opening about 4-5" up to the window frame flange (aluminum..aluminium for you i think). that is were a good bead of caulk and paint are needed the most. window sills must be sloped to prevent standing water.

i have inspected icf houses where people had leaks thought to be coming from the usual wall/stucco cracks or floor/wall transition joint, only to find that they had not properly sealed the openings and utility penetratios on the exterior walls. some had screws sticking out of the window frames/mosquito screens/hurricane shutter tracks that had oversized frame holes around them (which were not caulked), were sheet flow of rain easily found its way to the inside of the house.

if you provide your email address i'll gladly send you some pictures in about a week...

[email protected]
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[email protected]

Hi Peter, Thanks for that. I have pm'd you my email address. I spoke to one of the ICF suppliers this morning (Beco) and they said the same as you, i.e sealing around the windows and doors is by far the most important thing to prevent leaks. Thanks again. AA

AA
we have built/supplied icf's to about 250+ projects in south florida, including many in the keys and some other caribbean islands in the past 15 years. about 50% use hardi board siding, the rest stucco... mostly cementicious, very few synthetic EIFS...
there has never been a leaking or moisture problem with any of these...
we've had our share of stucco cracks, which occur with stucco on ANYTHING....
but after caulking the cracks and maintaining the transitions with caulk and paint there were no problems...one guy even claimed his windows leaked.. i asked him to turn on his sprinkler system, and sure enough, 3 sprinkler heads were shooting staight at the windows...
peter

How bout dealing with freeze thaw situations re: concrete roof in cold climate like MN?

Mr. aa_uk,

Here's the answer. This is a crystaline compound that gets added to the mix. Once the concrete consolidates and water hits it- the compound expands and seals up all the pores/micropores which makes the wall waterproof. We have used it before - works like a charm :)

http://www.kryton.com

Hi Baldwin. That's the sort of thing that I was thinking about. Out of interest, what does it cost over there? Similar ad mixes here add about 35 GBP per cubic metre, so I guess that's about 44 USD per cubic yard.

What I am really trying to find out is whether there is any reason why I shouldn't do it. e.g. causes damp in internal walls, makes your hair drop out, that sort of thing.
AA

no side effects.... other than cost... it is really not needed for regular walls... i would use it anywhere where you think your walls could come in contact with liquid water...
cant quite recall the pricing... dosage - i think its about a kilogram to 2 per cubic meter...