Duplex Slab Support in Oxford, IA

Thursday, July 20th, 2017 by Melissa Kremer

Challenge

A ranch style, slab-on-grade duplex had a stable exterior foundation but poor slab support conditions on the interior. The worst slab settlement was measures at 2 ¾ inches near the center of one of the unites. Evidence of the movement was visually obvious, including cracked floor tiles, gaps between partition walls and the ceiling, and interior doors that didn’t open or close properly.

Solution

MidAmerica Basement Systems proposed a solution to use PolyLevel 400 (PL400) ridged polyurethane foam to lift and support the settled areas of the duplex slab. PolyLevel is a two component liquid urethane system that when combined expands into a lightweight, ridged material used to fill voids, stabilize slabs and lift concrete. When installed, PL 400 typically weight only five to seven pounds per cubic foot (pcf). Other slab lifting materials can weigh upwards of 120 pcf, which can contribute to further slab settlement over time. With a compressive strength over 10,000 pounds per square foot (psf), PL400 has the strength to support residential and most commercial slab loading conditions.

PL400 was injected through small, 5/8-inche holes drilled in the slab, starting with the lowest areas. As the fill and lift operation continued, door function returned to normal and the visible gaps between partition walls and the ceiling closed dramatically. The area of slab that had settled as much as 2 ¾ inches was returned to within 1/8-inch of its original elevation. After observing the successful results, the customer asked the crew to expand the scope of work to other areas of the duplex. The project was completed in 11 hours using 470 pounds of material.