Residential Foundation Repair

Residential Foundation Repair, Virginia Beach, Virginia

Structural Engineer:  Glenn C. Otto, PE, A Structural Engineer, Virginia Beach, VA www.astructuralengineeronline.com

Problem:

Realtor listing house was concerned about multiple cracks in foundation. Inspection indicated that there was little settlement, but that the rear addition had experienced lateral movement. An independent (third party) Professional Engineer evaluated structure, concurred that there was little settlement, but that underpinning an area of the perimeter wall and stabilizing the slab would help to prevent future movement.  Other foundation repair companies had quoted 17 resistance piers or 11 resistance piers. A detailed survey of the house revealed that there was less than 2/10ths inch of difference in elevation across the same brick line around the entire perimeter of the house, which disqualified extensive settlement.

Previous attempts at foundation repair included tuckpointing (cosmetic masonry repairs) and concrete underpinning, which had been completed in the 1980s. The slab had originally been installed as a ground-level patio, and then enclosed. After the area was enclosed, the additional weight caused the slab to shift due to instability of the soil underneath, and the lack of a footer.  When the slab first shifted, the owner had someone pour additional concrete under the outside edge of the slab, which only made the structure heavier, and thus the problem worse.

Concrete underpinning (adding more concrete under the edge of a moving slab or foundation) is not usually a good foundation repair method. Particularly in this case, where the problem was due to instability of the underlying soils, adding more weight on top didn’t improve the situation.

Solution:

High density polyurethane foam injection for void filling under and slightly lifting the interior floor of the area. Underpinning with resistance piers to stabilize the perimeter walls.  2-pound high density polyurethane foam was installed, along with four ECP Model 250 concentric piers. Concentric piers were chosen to accommodate previous concrete underpinning work. The load calculations used to design the repair system took into account the excess weight applied to the structure by the previous concrete underpinning.

Results:

Concrete Jack underpinning and foam jacking crews worked together to stabilize and secure both the interior floor and the exterior walls using the most effective methods for each. The foundation repair work was completed over a period of two days. After the work was completed, owner was able to address cosmetic cracks in the brickwork and offer a repair with a transferrable, 25-year warranty to potential buyers.