Waterproofing
CSI Division 07, Thermal & Moisture Protection
Membrane or coating systems applied to building elements below grade (foundation walls, below-grade slabs) or in wet areas to create a continuous barrier against water intrusion, distinct from "damp-proofing," a lighter-duty treatment that resists moisture but isn't rated to hold back standing water or hydrostatic pressure.
Why it matters
Confusing waterproofing with damp-proofing is a common and costly mistake: a below-grade wall subject to real hydrostatic pressure (water actively pushing against it) needs a true waterproofing system, and a lighter damp-proofing treatment applied in that situation will eventually fail once groundwater conditions create real pressure against the wall.
On a real project
A building with an occupied basement below the water table uses a fully adhered waterproofing membrane on the foundation walls, rated specifically to resist hydrostatic pressure, rather than a lighter damp-proofing coating that wouldn't hold up under those groundwater conditions.
Who this matters most to
A specialty waterproofing crew, often working alongside a Concrete Worker, applies the membrane before the foundation is backfilled, since it's essentially impossible to fix once soil covers it. A Quality Control Manager inspects the waterproofing membrane for continuity and proper detailing at penetrations and corners before backfill is approved.
Where this goes wrong
A project substitutes a damp-proofing coating for the specified waterproofing membrane on a below-grade wall to save cost, reasoning that the site "doesn't seem that wet." A few years after occupancy, seasonal groundwater rises high enough to create real hydrostatic pressure against the wall, and water finds its way through the damp-proofing into the finished basement space below, a failure specifically avoidable by using the originally specified system.