Foundation & Basement Waterproofing
When a waterproofing paint isn’t enough, you need a membrane. Rubberseal Black rolls onto damp (not wet) concrete and cures into a seamless barrier built for continuous ground contact — the same approach commercial waterproofers take, in a bucket you can carry.
Paint vs. membrane: why it matters below grade
Waterproofing paints are thin and rigid; against the constant pressure of wet soil, they crack and let water find a way in. A membrane is different — a thick, flexible, seamless layer that moves with the wall and bridges the shrinkage and settlement cracks that let basements leak. Rubberseal Black builds a true membrane at a real film thickness, not a paint-grade coat.
Why Black for foundations
Below-grade walls are in continuous contact with damp soil and ground water — the definition of a standing-water job. That’s Rubberseal Black’s specialty: our strongest, true-waterproofing membrane, made in the USA and built for exactly this kind of constant water contact. White and Gray are for roofs and exterior surfaces above grade; for foundations and basements, use Black.
Where to use it
- Exterior foundation walls (below-grade waterproofing)
- Basement and cellar walls
- Retaining-wall backs
- Footings, grade beams, and planter walls that hold back soil and water
- Concrete and masonry structures in continuous ground contact
Built for damp concrete
Foundations are rarely bone-dry. Rubberseal Black is formulated to bond to damp (not wet) concrete and masonry with proper preparation, so you’re not waiting days for a wall to dry out. It can even be applied to green concrete once forms are removed and the surface is surface-dry — see the application guide for details.
How to build the barrier
Clean and repair the surface, seal or divert any running water, then apply Rubberseal Black in multiple coats with a 3/8-inch nap roller or trowel between 50–95 °F. Reinforce cracks, cold joints, corners, and pipe penetrations with Rubberseal Geotextile fabric embedded between coats. For below-grade waterproofing, build to at least 60 mils dry film; for damp-proofing, at least 30 mils. Full cure is about 72 hours at 70 °F.
Coverage: about 32 sq ft per gallon at 40 mils. Estimate your project with the coverage calculator.
Surface preparation matters
The wall must be structurally sound and free of dust, oil, grease, curing compounds, and loose material. Complete structural repairs first, then reinforce detail areas with geotextile. Good prep is what separates a barrier that lasts from a coating that peels.
Common questions
Can I apply it to a damp basement wall?
Yes — Rubberseal Black bonds to damp (not wet) concrete with proper prep. Stop or divert any active water flow first and complete structural repairs.
How thick should the membrane be?
At least 60 mils dry film for waterproofing below grade, or 30 mils for damp-proofing — built up in multiple coats.
Is this better than waterproofing paint?
For continuous ground contact, yes: a flexible membrane bridges cracks and resists standing water in a way a thin, rigid paint cannot.
Not sure it’s the right fit? Talk to technical support at 866-607-6826.