Yes, generally you will need a waterproof coating of some kind on the below grade ICF. You don't use tar because it will attack the EPS foam. Just google ICF waterproofing or similar terms for more info.

Common practice around here is to use a 60 mil thick peel-n-stick rubberized asphalt membrane applied directly to the exterior foam or over a primer coat applied to the foam first. A rubberized mastic is then applied to all seams, joints, and terminations. Then some sort of backfill protection board or dimpled plastic membrane which allows water to flow down to your footing drains is applied over that.

Single ICF pours are typically limited to 12-14 feet in multiple 3-4' lifts of concrete. So, a main floor over a basement would require 2 pours. For an all ICF home with one floor over a basement, you will generally form up and pour the basement wall first. Then construct the floor system so that you have something to work on. Then form and pour the main floor. With this type of construction, you will typically have two cold joints; one at the interface between the concrete footing and the basement ICF wall and another between the basement wall and the main floor wall.

Photogman,

First, you need to understand that there is damp-proofing (DP) and water-proofing (WP). Most single family projects are NOT typically WP because of cost. I preference WP over DP simply because of the cost to remedy a leak and a foundation is such a large investment why would you jeopardize your investment. Also, I would look at the system being used and ask the questions about warranty and how long the company has been in business to support you in case there is an issue.

Second, a cold joint is inevitable with multiple levels. Remember it's the rebar/reinforcing that is tying the levels together. Concrete itself is used under compression only and has very little tensile strength so it's the rebar that is providing the strength under tension where you have a cold joint. You have nothing to be concerned about with a cold joint. I would consult with an engineer if you have concerns and they will support this explanation. I would be glad to discuss further if you have any other questions.

Sincerely,

Andrew Hobbs

I also recommend a minimum of two membranes, such as peel and stick and dimple board.

I too am interested in this topic. I am pouring an ICF stemwall for an insulated slab next week. The very cheapest waterproofing I can find is $35 for about 100 square feet and this is a spray on product
The peel and stick runs closer to $150 for 200 square foot of coverage.A rep for insulfoam told me that waterproofing is not really necessary for my application, and the foam will hold up just fine below grade without it. I was thinking about using 6 mil plastic then cement board and/or asphalt impregnated fiberboard before backfill. Any advice? (Thanks)

vb,
The use of peel and stick, or something similar, would be a good idea for any subsurface situation.
While waterproofing is not critical for your application, the barrier will also help keep underground critters from
digging into the foam.

vb -- i hope it's a retaining wall. If you have living space on the other side you will probably find that code requires at least a waterproof membrane for below grade. If you are in an area with no code i wouldn't "get away with it" unless i really didn't care about water penetration. Regards.

Texas ICF,
This is just a footing and stem wall for a slab. (not to be confused with the original poster "photogman" who is doing an ICF wall).
I called Arxx ICF yesterday and they are telling me that I need no waterproofing for my application. What I am getting from this is - If you have a living space behind the wall, waterproof. If you are backfilling both sides of the wall, the foam block is stable on its own and not waterproofing will help it to not retain water (unless you have a high water table then these rules change again). Taking wes's advice to heart, I may still use something to block the critters though. As a side note I have looked very hard for a peel and stick product locally and nobody has any thing in stock. (Seattle). One week out minimum.

The ICF coatings are very nice, I got some samples. One sample has a waterproofing that looks like it is the same as their base-coat for above grade. I like the idea of applying the base-coat from footing to roof and covering the above grade with a finish coat.

Posted By ICFconstruction on 14 Mar 2010 09:32 PM
The ICF coatings are very nice, I got some samples. One sample has a waterproofing that looks like it is the same as their base-coat for above grade. I like the idea of applying the base-coat from footing to roof and covering the above grade with a finish coat.

ICF construction, Where did you get the samples?