My contractor wants to stick build my back basement wall as its a walk out basement.  He will build a 4' frost wall to code then come up one course of ICF block and stick build the rest of the wall.  I really dont want to get into a thermal mass discussion.  my question has to do with the stick built wall on top of the single course of ICF and were and how he wants to center the wall.  8" wall icf with form is 12.5"  using a 2X10 the actual dimension is 9-1/4".  He wants to put the Wall frame off center on the concrete section of the ICF wall so the 2X10 framed wall plus the sheathing is flush with the foam of the outside of the ICF.  I am building a modular and the modular company also says that the exterior dimension have to be perfect 27'4" X 48"  so the only way to do this is to off center the stick built wall on the concrete.

So if my math is correct the 8" concrete and the outer 2 1/4" of foam of the ICF equals 10 1/4"  and a 2X10 (actual 9 1/4") and 7/16" OSB sheathing equals 9 11/16"

So this means on the concrete portion of the ICF 9/16" of the concrete will not have the wall studs on top of it but the entire out foam will.  I dont really know what I am doing but this seams like the wall is off ballanced.  Should he use 2X12 will have the same off ballance but at lease all of the concrete section of the wall will be convered?

has anyone done this please dont say just build the back wall with ICF I know that is an option.

sligar38 - Off centering a small load like this is not going to be an issue. Basement walls have been frame off center for years. In a cast in place basement the wall would have been 8 or 9 inches thick with the wood wall framed up from the outside. That would leave a much larger portion of the concrete uncovered. That is why in many home you see a ledge on the inside of basement walls. If the wall was 16" thick there would be no need to cover the whole 16".

In your case your concern should be if there is weight on the foam, which of course the will be very little. Assuming this in on the long wall of the modular, the joist of the home will be sitting on the 2 x 10 top plate which will transfer the load through the studs to the concrete.

Assuming this is a single storey modular and the basement is not more than 9' high, in reality a 2 x 4 wall with the lead edge over the front edge of the concrete core, would carry the load so it depends on what you reason for using the 2x10 was. From an insulation point of view, I would put 2" of eps on the outside and reduce the framing to 2x8 or 2x6.

One solution would be to use a Taper Top ICF form so you have a larger concrete surface to work off.

All your calculations are for perfect world.
But the world is not perfect.
My ICF walls are half inch longer than my calculations if they are are more than 25ft.
ICF walls are becoming longer after pour.
Using Taper form will help.

Thank FBBP the 2X10 if for insulation purposes I wanted to make sure I got a high R value but want to be able to add on to the home in a couple years so the contractor is using wood instead of ICF the home is a two story and yes the contractor told me there would be a ledge on the inside wall which I am fine with.

I appreciate you putting me at ease with this the off center wall to the concrete scared me I am not a builder but I know when you use child building blocks and you off center them when you stack them they fall over.

How do I know if there will be a load on the foam as the 2 X 10 will cover it?

Posted By sligar38 on 03 Sep 2013 12:34 PM
Thank FBBP the 2X10 if for insulation purposes I wanted to make sure I got a high R value but want to be able to add on to the home in a couple years so the contractor is using wood instead of ICF the home is a two story and yes the contractor told me there would be a ledge on the inside wall which I am fine with.

I appreciate you putting me at ease with this the off center wall to the concrete scared me I am not a builder but I know when you use child building blocks and you off center them when you stack them they fall over.

How do I know if there will be a load on the foam as the 2 X 10 will cover it?

In this case the the foam will simply crush a little and letting the concrete take all the load.