The alternative was to completely remove the failed subsurface drainage system on the outside and replace it with new washed drain rock and four-inch perforated drain pipe. While the dirt-side of the wall was exposed, we reapplied the ICF factory-recommended stick-on membrane system. In short, if we couldn’t make the wall waterproof, we’d keep water away from it.
The most difficult section was the wall adjacent to the garage. To access and install an effective drainage system, we had to saw-cut and remove a strip of the garage slab. This was no easy matter, considering there was only about nine-foot vertical clearance from slab to roof trusses. A miniature excavator was used, which saved a bunch of hand digging.
Now the structural issues. The contractor did such a poor job with the ICF, he wound up needing a heavily shimmed, triple mud sill at the top of the wall to ensure level floor joists. Anchor bolts were spaced six feet apart and did not penetrate all three mud sills. As a consequence, there was virtually no structural connection between the top of concrete wall and floor diaphragm.
A little theory: there are two types of poured-concrete retaining walls: cantilever and braced (or propped). Cantilever walls do not depend on a top-of-wall connection to a horizontal (floor or roof) diaphragm to keep the top of the wall from deflecting inward due to the pressure of soil. Braced walls do. Cantilever walls typically have much larger footings and more rebar than braced, so are more expensive. Basement walls are generally designed as braced because there is nearly always a floor diaphragm handy, and they’re cheaper.
The subject wall was no exception. But with the shoddy mud sills/anchor bolts, the soil’s inward thrust could not transfer to the floor diaphragm. So, in time, it is likely the top of the wall would have caved inward.
The remedy was to rotohammer and epoxy custom steel brackets to the top of the wall and then bolt them to the floor joists — a difficult, expensive and time consuming process.
In the bitter end, the contractor went bankrupt and the home owner wound up paying for the repairs himself. Tack on attorney and expert witness costs, and you wind up with a very ugly situation indeed.
As usual, everyone would have been much better off if the contractor understood what he was doing and had done it right the first time.
Tim K. Garrison, P.E., M.S.C.E., of ConstructionCalc.com, has authored a book and several short courses and lectures on topics relevant to builders. He can be reached by e-mail.
The views expressed in this article represent the personal views, statements and opinions of the author and do not necessarily represent the views, statements, opinions or policies of the National Association of Home Builders. NAHB does not necessarily endorse any of the views expressed by the author and NAHB is not responsible for any direct or indirect consequences arising out of the views expressed in this article.