Our property is sloping, and is just the right grade for a walk-out basement, which is our plan. I've looked into conventional poured walls, and Superior wall, which is pre-cast off-site and then assembled. One thing I was cautioned about is the unequal pressure on the foundation walls, since the uphill side will be fully buried, and the downhill side fully exposed. In a fully buried basement, the idea is that the load is equal, and the flooring handles the compression load. Superior won't do more than a 30' wide uphill wall unless it either has a jog in it, or added shear wall(s). How will ICF do in this application? The soil is clay-based, but not considered excessively expansive. I'll be backfilling with gravel to drain water away to the perimeter drain. Are there any changes done to ICF for this application? Is it wise to go to a thicker block? Thanks for any input.

The length of straight wall is dictated in the building code and has several variables, one being type of soils and height of soils.

In regards to the 'unequal' pressure, this can be compensated with a larger footing, thicker ICF wall (say 8" vs. 6"), etc.

I recommend you seek the advice and design of a local engineer who understands the local area which you are building in.

I very common occurrence here, since almost all houses have basements and most are walkouts. The engineers or 2006 IRC that MN uses makes no difference with a walkout. Use code or ICF manufacturers engineering and you should have no problem.

I think the problem is making a long wall out of segments of precast concrete, not the "unbalanced" foundation  The precast to precast joints do not resist moment and the wall will deflect unless there is a big beam across the top.  They must not be confident that the diaphragm created by the floor has sufficient stiffness.

Should be no problem with any type of cast in situ concrete.  In any case, involve an experienced engineer.

Bruce

I readily agree with Bruce's comments.  I have learned my lesson after losing just one precast bolted together wall.  In my humble opinion, a site cast wall would not have failed.  My client had to pay to replace the precast wall with a cast-in-place wall.

I second that. In my 18 years of consulting, now only part time, I have never seen a poured concrete wall, cast in place, or site cast damaged due to back-fill or hydrostatic pressure. It was almost always CMU and a few wood foundations. Thankfully wood foundations are done and Superior walls haven't done a lot around here.

What you are planning is what we just did in (warmer) Virginia but in similar soils.  We used a styrofoam/concrete block product called Tech Block, with lots of seams.  We were worried about pressure and leaks.  Just to be safe on this count we did two things.  We used a product called Form a Drain to create drainage around both sides of the footers and then had an engineer design a system using a buffer zone of rock and an additional footer tile drain 3' out from the wall on the buried side.  While this cost a little more, the design pressure at the bottom of an 8' tall wall was greatly reduced.  So far it has survived pressures caused by the rain dumped by two hurricanes that passed through.  It also does not leak anywhere. 

We have sold and or installed many ICF basements that where walk outs of the same catagory. As long as the floor deck is installed before backfill most walk outs would not be a problem. Give us a layout so we can determine your situation.

Dave