The Elmwood Franklin School had been experiencing continuing settlement for several years. The school engaged McMahon & Mann to explore the causes for the settlement and to recommend remedial options to arrest the settlement. The settlement is limited to the portion of the building with a crawl space.

The cast-in-place first floor is supported by footings constructed on a clay subgrade. As shown in the above photograph, the subgrade has dried over time from actively ventilating the crawl space.

McMahon & Mann drilled borings inside the existing crawl space and outside of the school to collect samples for moisture content analysis. We observed that the soil below the interior footings had dried to below the bottom of the borings. We recommended that the school maintenance department hydrate the subgrade and have its surveyor establish a series of observation points on the structure to monitor the structure’s response to the subgrade hydration. The survey data show that the clay swelled after it hydrated and that the floor heaved and the cracks in the walls closed.