I may be working on an small single story house underpinning project in the future (if the deal goes through). I've worked on a few different underpinning projects (mainly some big houses in TX my dad owned years ago) and am familiar with the procedure and safety/structural concerns. This particular home is only 800 sq ft, not much weight but enough to take precautions and do things the right way. The soil is undisturbed clay, and is very dense/hard to dig. The project is lowering the crawl space floor a bit.
As I see it, the piers I'll be forming & pouring would be about 4' tall, 3' wide and 12" thick (and thicker in places). The existing red brick foundation is 4" thick and 12" thick at various intervals (where interior walls meet the rim joist). I'll also be setting some drain tile below (beside) the piers, to wick off any water that may otherwise settle behind the piers.
The piers would need to be joined together with rebar. With these being taller than I've poured in the past I'm not sure what the general rule is for setting rebar in the forms. Is there a standard rule to follow per thickness of pier/form?
I was thinking of running 3 lines through every pier, each about 12" on top of the other. Figure 3 would be plenty to keep the piers attached and acting as a single unit. Or should I go with 2 every foot (6 per pier)?
Last edited by montana_bound; 09-18-2012 at 11:12 PM.