Poly (polyethylene vapour barrier) and rigid styrofoam (EPS or XPS foam board) are two related products that together do most of the work of keeping a foundation dry, warm, and protected. They go in after damp proofing and before backfill - usually on the same site visit, often as part of the same crew day.
Rigid foam board on the exterior of a foundation wall does several things at once. It adds thermal resistance, which matters a great deal for finished basements. It protects the damp-proofing membrane from being torn during backfill (rocks, roots, the bucket of an excavator). And it helps keep the wall temperature stable, which reduces the condensation that drives interior moisture problems. We install 2-inch EPS or XPS depending on what the project calls for, with staggered seams and a finish protection at grade.
Poly vapour barrier is the other half of the system - under slabs (where it prevents ground moisture from wicking up through the concrete) and on the warm side of interior framed walls in finished basements. Continuity matters: every seam taped, every penetration sealed, no skipped corners.
We do poly and styrofoam installs across Surrey, Vancouver, and Burnaby - almost always alongside rebar and damp proofing on the same project. Bundling makes everyone's job easier and brings the price down. Call and we will quote the whole below-grade package.
