What is polyurethane foam injection?

Polyurethane foam injection is a liquid sealant pumped directly into cracks, joints, and leaks in concrete and masonry. When injected, the material expands to fill gaps and voids, then hardens into a closed-cell foam that repels water while remaining flexible enough to move with the structure.

This method works best on active leaks and cracks that continue to shift, because the sealant accommodates minor wall movement without cracking or separating. Unlike rigid epoxy repairs, which can fail if the surrounding concrete moves, polyurethane foam's elasticity allows it to absorb slight structural stress.

Typical applications include active basement seepage, moving foundation cracks, control joint leaks, and gaps around penetrations. The foam expands to seal spaces that would be difficult to reach with conventional caulking or patching. Installers drill small access holes, inject the foam under controlled pressure, and monitor expansion to avoid pushing walls out of alignment.

Because polyurethane foam injection targets actively leaking areas rather than prevention, it is often used alongside other basement waterproofing strategies. The material is water-activated, meaning moisture in the crack actually triggers the expansion, which makes it particularly suited to basement environments where dampness is constant.