Settling Garage Floor Slab – Causes

As with most slab settling issues, voids and poor soil compaction are at the root of the problem. This is certainly the case with sunken garage slabs. They are typically constructed by backfilling the area after the foundation is poured (or blocked) and pouring the concrete on top. Achieving proper and adequate compaction is often difficult and just not achieved in many cases. This, combined with time and freeze/thaw cycles creates voids under the garage slab. Concrete itself is heavy and can settle, but when we park vehicles on top of a garage slab that has voids under it? It is obviously a recipe for disaster!

Settling Garage Floor Slab – Solution

Alchemy-Spetec can refer you to a contractor for a thorough site evaluation. A qualified contractor takes the time to properly inspect the issue, which generally entails probing the slab to determine if there is indeed a void and/or unstable soil (and to what extent). Gathering this type of information is key to designing a proper repair plan and calculating the amount of polyurethane lifting material needed.

Depending on the conditions found during site evaluation, there are a couple of different techniques the contactor may use (and oftentimes both). If the soil under the garage slab is soft and unstable to a certain depth, they may opt for the Deep Lift® method. The expanding structural foam creates a squeeze effect in the loose soil, essentially forming added support footings under the slab. The other injection method, Slab Lifting, entails going through ⅜-inch holes drilled directly through the slab. The same structural foam described above is used. The expanding foam travels the path of least resistance, therefore, filling all void areas as well as compacting any loose soil. Once the soil is compact, the expansion of the foam creates the power to lift the slab. Our high-density polyurethane cures to 90% in fifteen minutes – which translates to the slab being traffic-ready by the time we are packing up our equipment.

Want more info on the Deep Lift® and Slab Lift methods?