helical vs concrete piers (cost effectiveness)

[renRosen]

Hello,

I'm starting the process of having built for me a home (2700 sf) on a hillside outside of San Francisco. The slope is pretty severe (1(rise)/2(run)). Bedrock is around 10 feet down. Foundations here are very expensive ($100K-$200K) and almost always use concrete piers and gradebeams. I've heard that helical piers are ofen less expensive and quite effective, but they don't seem to be used very often here. I'm trying to figure out whether helical piers can be used on a job like this and whether they tend to be more cost effective. Any insights (including thoughts on other foundation systems which could be explored) would be greatly appreciated.

Thanks,

Larry Rosen

 

[GeoPaveTraffic]

I would stick with concrete piers and grade beams. They have the advantage of being a stiff system, whereas most of the helical piers are not very stiff. Another consideration is that concrete piers can be ground partway into the surface of the bedrock, the helical piers cannot be.

Given the potential for earthquake loads and slope/mud slides in the area, I would go with as stiff a system as possible well tied together. That way if one pier fails, the others can take the load and keep the house from moving.