Remediating Surface-Pour Foundation Issue

CA - Bay Area.

The Scenario:

This is a non-residential outbuilding on a residential property. ~40'x24'. When we purchased we were told the this building had a standard perimeter foundation. We expected that to mean that there was a standard subterranean footing.

Upon clearing some weeds and brushing back some dirt we found that this is not the case - it was a surface pour that at best extends 3" below the surface.

The foundation has not failed at any way. It's a pretty hefty pour and appears to have rebar in it. So that's good. The bad is that as a surface pour, water from rain will just flow under the building. This has made entire sections of the dirt right under the foundation powder soft. This worries me, a lot.

The Plan:

We simply do not have the money to jack the whole building up and do repours all at once. This would be the ideal solution, and really the only proper one. I fully understand this, but I'm working with what I can here.

The best we've come up with is to dig out "saddles" every 4 feet or so:

Railroad tie under building, bottle jacks and temporary support beam to take part of the weight off short sections of the foundation.

Dig 2'-3' wide (along foundation), 3'-4' deep, and a foot or so past (perpendicular to foundation)

Build rebar cages in these holes, drill & epoxy into the undersides of the old foundation.

Pour concrete and let set.

Repeat down the length of the foundation over the next several months. Then come back thru and repeat for the sections between the saddles, tying everything together with more rebar.

I know that joining two pieces of foundation together is never great no matter how well you clean and prep the previously-poured concrete, but I'm hoping that in this case it largely doesn't matter since all I'm interested in doing is creating a solid bed for the existing, still solid foundation to sit on top of.

Doing it piecemeal like this makes it more immediately affordable and I don't need to jack the whole building up to do this. It starts providing stability immediately (presumably) vs me saving for a few years to be able to do the whole job at once.

The Question(s):

Before we break ground, is if this worth doing - do I risk doing more harm than good? In what way(s)? Or should I "just" save for 2-years or so and do it right, risking failure due to water infiltration and/or earthquake in the interim?

First thing I am doing, regardless, is digging a french drain & adding gutters to try and help divert the water away from the building.

Submitted July 01, 2016 at 10:01PM by Revlis-TK421 http://ift.tt/29bcvUj