This may be a dumb question, but is Tyvek or other weather shielding required or desirable over ICF? I'm going with fiber cement clapboards over furring for a drainage plane. I can't imagine water ever reaching the ICF, but I need to know what the best practice would be. Thanks!

I wouldn't recommend it - would make locating your furring strips pretty tough.

I'm not sure if there would be a point to it. Tyvek is for stopping air movement in the walls and preventing moisture from getting in. The foam already does that (arguably better, too).

Tyvek is sold as vapor-permeable water resistant drain plane material, not an air barrier.

While not inherently an air barrier, it's possible to detail it to be an air barrier when siding fastener penetrations will be few in number.

Even XPS rigid board isn't considered a suitable drain plane & weather resistant barrier unless detailed with appropriate tapes in a Z-flashing configuration on every horizontal seam, and a surface application on vertical seams. This just isn't gonna happen as a retrofit on ICF block seams, and SFAIK most builders don't. While EPS isn't an inherent water resistive drain-plane, but with a 3/4" rainscreen gap you probably wouldn't have much of an issue except at window & door penetrations where you can't properly lap the flashing to the drain plane.

The issue is most-often treated with purpose-designed window/door bucks to handle the bulk water loads that lap the EPS properly top & bottom, and flash the window to the buck. (This VERY important detail to get right.)

Using Tyvek as drain plane would allow flexibility for lapping the drain plane & window & door flashing at the tops of the windows/doors for long term & reliable redirection of bulk water to the exterior. Whether it's necessary or not may depend on how well the window bucks & windows went, but I suspect most builders would opt to skip it unless something was really askew. (I haven't worked with above-grade ICF enough to know how problems with those details get fixed in the field.)

I have seen Tyvek used just around doors and windows, probably to help with the flashing. Since I'm doing the work myself, I can take whatever pains are necessary to ensure proper flashing.

Rather that Tyvek, why not just use 6 mil polyethylene plastic sheeting?

I wouldn't recommend it - would make locating your furring strips pretty tough.

Housewrap has hash marks every 8". If you line them up with your strips when you apply it, there is no problem at all.

Is Tyvek commonly used in ICF homes to wrap around windows and doors?

Do you mean around the window and door openings? That's what everyone felt compelled to do on my build. In a home that is going to be fully caulked and sealed I didn't see the point, but I guess I didn't push hard enough and now, I am cutting all the extra flaps off to avoid having yet another piece of something passing from outside to inside. Looks to me like all it does is make it harder to get a good seal between the wall and window with backer rod and sealing foam.

Posted By ICFHybrid on 23 Jun 2012 09:06 PM

I wouldn't recommend it - would make locating your furring strips pretty tough.

Housewrap has hash marks every 8". If you line them up with your strips when you apply it, there is no problem at all.

Have to be careful to keep it perfectly level and straight.  Also - if you have 6" o/c webs this would not work as well (I guess every 3rd one will line up).

Have to be careful to keep it perfectly level and straight.

Ha Ha, yeah, ....so?

Also - if you have 6" o/c webs this would not work as well (I guess every 3rd one will line up).

I have routinely seen them remarked if the two systems aren't compatible. Not a big deal for someone who cares about the job and a good argument for keeping your strips lined up from top to bottom. WIth ARXX block, you can also feel the strips as they are on the surface.

All the major ICF manufacturers carry ICC approvals, if you read them they contain all the information needed to appease the building departments. They address the need for house wraps and vapour barriers as well as the performance of their products.

Generally speaking house wrap is not needed on ICF, however some jurisdictions still require for whatever reason, presumably they can't read the ICC reports properly or choose to ignore them or choose to give you restrictions simply because they can.

ICF is a great product and can be very cost effective compared to 'conventional' construction methods...provided it is built using the proper methods as it was designed for, however as soon as you start overbuilding it (not that there is anything wrong with that) you are spending money needlessly on additional products not required.

If you have a second storey over say a porch, how would you get your drain plane over your roof to wall flashing without using some type of housewrap? Same with windows that are not tucked under soffits. If water penetrates the cladding, all vertical icf joins will allow it to get behind the flashings.

There is a detail on cutting the foam and inserting a bent metal flashing for the areas you describe. Also your point is valid, but also keep in mind Tyvek is not waterproofing either, it's an air barrier. If you have water penetrating or getting behind the facade of the structure you have a bigger problem to address.