So I have a lot I'd like to build on, but it has expansive soil. A solution to it is to install micro-piers. These would be 20'-40' deep x ~4" holes drilled every ~8' under the foundation walls. They are then sleeved, rebar installed, and concrete poured into them.

I'm just wondering if anybody here has experience with this type of construction when using ICFs. We'll have a full basement. Is there differences in the construction of the ICF wall in this case?
Thanks all!

Have you consulted with a soils engineer? Lightweight structures are more at risk for damage from expansive soils. The heavier your build, the less it is a factor. ICF is heavier than stick construction and you may be able to engineer out the necessity for things like micropiers. They sound expensive.

I take it you're planning on drilling the holes yourself since you have the drilling equipment, right? Why do you need the sleeves? Isn't the soil stable enough to stay open until you pour the concrete? Since you're going to have a relatively light load and load is pure compressive I think you might be able to get by without rebar. Now that I think about it you could do these piers just like you install loops for geosource heat pumps, couldn't you? Install some rebar just like you do refrigerant tubing. I remember I was considering having you, or your company at least, come and drill the wells I was going to need when I was planning on using a direct exchange heat pump.

Don't discount using wood pilings. They're used every day in Louisiana, 20', 40', 60' deep, however many it takes to get the required load bearing capacity based on driving friction. I'm sure the piles would be cheaper but don't know how the cost of driving would compare with you doing your own drilling.

You can drive wood piles, screw in helical piers (some of which pull in concrete) or build a frost protected thickened edge slab, possibly post tensioned, that creates a bearing area so large that the soil will support it. I'd lean towards the FPSF but of course your engineer is the best source.

Posted By tuffluckdriller on 25 Oct 2013 01:46 PM
So I have a lot I'd like to build on, but it has expansive soil. A solution to it is to install micro-piers. These would be 20'-40' deep x ~4" holes drilled every ~8' under the foundation walls. They are then sleeved, rebar installed, and concrete poured into them.

I'm just wondering if anybody here has experience with this type of construction when using ICFs. We'll have a full basement. Is there differences in the construction of the ICF wall in this case?
Thanks all!

We have use minis in commercial construction but in our case we used 5" heavy wall pipe down to bedrock (between 17 and 30 feet) and filled them with grout. The pipe is the strength and the grout prevents bending. I don't think this will work unless you have bottom bearing.

If you use piles, what will you do to prevent the floor from moving?