Waterproofing & Moisture Control

Build Dry From the Inside Out Finishing over damp concrete guarantees long-term problems. Before framing, inspect foundation walls for cracks and efflorescence. Apply a cementitious waterproof coating or vapor-permeable membrane to block liquid water but allow vapor diffusion. Follow with dimple drainage mats that channel any seepage down to a perimeter drain or sump pump....

Protect From the Outside In—and the Inside Out Long-term waterproofing begins before finishes. Start with an exterior drainage system whenever possible—footing drains wrapped in filter fabric, a gravel trench, and waterproof foundation coating. Where excavation isn’t feasible, interior retrofits combine vapor barriers, drainage mats, and sump systems to redirect water safely. Key Layers of Protection...

Treat the Well as a Mini Roof Drain An egress window well is a collection basin unless it has a controlled path for water to leave. Start by grading soil away from the foundation at 5% for at least 10 feet where possible, then build the well as a rigid collar (galvanized steel or concrete)...

Design the Assembly, Not Just the Tile A below-grade bath lives or dies by its assembly. Start with a continuous vapor/waterproofing membrane (sheet or liquid-applied) tied into a factory-formed drain with clamping flange. On slabs with dips, self-level first, then slope the shower area at 1/4″ per foot toward the drain. Use a bonded flange...

Design for Redundancy, Not Just Capacity NYC’s cloudbursts and utility blips mean a single pump is a single point of failure. Specify a sealed, gasketed sump basin with a clear cover (to limit humidity and odors) and dual pumps: a primary high-output AC pump and a secondary DC pump on an independent deep-cycle battery. Add...

Match the Solution to the Water Source Exterior waterproofing (excavation, footing drains, membranes) tackles bulk water before it reaches the wall—ideal for chronic seepage or hillside lots but costly where access is limited. Interior French drains with a sealed sump intercept water at the slab edge; they’re highly effective for hydrostatic pressure and can often...

Think Source, Path, and Pressure Effective basement moisture defense addresses the source (groundwater, surface water, humidity), the path (walls, slab, joints), and the pressure (hydrostatic and vapor). Start with exterior grading and downspout extensions to move roof water well away from the foundation. Add or rehabilitate footing drains where feasible; when exterior work is limited,...

Start with a Bulletproof Perimeter Eaves and roof-to-wall joints are the most common leak points in finished attics. Sequence drip edge over ice-and-water shield at eaves, then underlayment laps correctly up-slope; at sidewalls and dormer cheeks, use step flashing layered with WRB counterflashing, never face-sealed caulk alone. Extend self-adhered membrane at valleys and around penetrations,...

Design a Fully Contained Wet Zone In an attic ensuite, moisture loads are concentrated and close to the roof deck. Build the shower as a tank: slope the pan (1/4″ per foot) to a linear drain, wrap floors and walls with a bonded waterproofing membrane, and flood-test before tile. Use cement board (not green board)...

Flash First, Then Insulate and Seal Begin outside with manufacturer pan flashing kits, continuous underlayment, and correctly sequenced drip edge so wind-driven rain can’t back up. Verify slope requirements and avoid placing units where intersecting valleys complicate drainage. Once watertight outside, focus inside: build straight, smooth shafts and line them with continuous insulation (rigid or...