Vapor Barrier Installation in Santa Cruz, CA

Local Context

A Santa Cruz Crawl Space Stays Damp Long After the Rain Stops

The moisture cycle under a Santa Cruz house has two halves and no gap between them. From November through April, around thirty inches of rain saturates the ground beneath a raised foundation. From June into September, the advection fog that pushes in off Monterey Bay most mornings holds humidity high even on dry days. Bare soil under a sub-area gives that moisture up into the crawl space continuously.

What it does up there is predictable. Subfloor joists and the sill plate take on moisture, which is what wood-decay fungi need to establish and what western subterranean termites (Reticulitermes hesperus) are looking for when they build tubes up the piers. Damp fiberglass batt between the joists slumps and stops insulating. In the low-lying parts of the city — the flats near the San Lorenzo River, the ground around Neary Lagoon — a shallow water table adds to it.

This is why a vapor barrier shows up as a Section 2 recommendation on so many Santa Cruz WDO reports. It corrects the condition that keeps producing Section 1 findings under a raised foundation, which is why inspectors write it up long before there is damage to repair.