Unbalanced Fill – Structural Failure

slab bowing

All was going well with the inspection of this home built in 2005 until started on the garage. Upon inspection, I found a gap between the slab and the foundation wall.

This gap at the rear of the garage started at 1/8″ at the ends to 2″ + at the middle area of the rear wall. Garage slabs are poured after the foundation wall is back-filled, therefore the wall has moved since back-fill and the pouring of the garage slab.

Behind the garage is an exterior grade difference of 8′. Foundation walls should have no more than 30″ of unbalanced fill unless specifically designed as a retaining wall.

Based on the thickness of the foundation wall, the wall did not appear to be designed as a retaining wall. Another clue was that the adjacent wall in the basement was poured in a stepping down configuration, which would be consistent with the placement of back-fill material behind the garage.

The Purchaser contacted the architect-engineer for the home. It was confirmed that this garage wall was to be back-filled to within 30″ of the top of the garage slab. As constructed, this foundation wall would likely continue to fail. They are working on a solution to this construction defect.