What makes elastomeric coating different from regular masonry paint?

Elastomeric coating is much thicker and more flexible than standard paint. Its rubber-like elongation lets it stretch over hairline cracks as the wall moves, rather than cracking with the substrate. Standard masonry paint is too thin and rigid to bridge surface cracks.

Will elastomeric coating stop water leaks in my block or brick wall?

Elastomeric coating effectively stops incidental rainwater penetration through porous surfaces and hairline cracks on above-grade walls. It is not a solution for walls with hydrostatic groundwater pressure, active efflorescence from internal moisture, or structural cracks that continue to move. Those problems need drainage and structural correction first.

How long does elastomeric coating last?

Most quality acrylic elastomeric coatings last 10–15 years in normal residential applications. UV exposure, temperature extremes, and surface prep quality affect longevity. Signs of end of life include chalking, peeling, cracking, and loss of the rubbery feel.

Can elastomeric coating be applied over old paint?

It can be applied over intact, well-adhered existing paint, but loose, peeling, or chalking paint must be removed first. If old paint is not bonded well, the elastomeric top coat will pull it off. A test patch is recommended to check adhesion before committing to a full application.

Does elastomeric coating trap moisture in the wall?

Quality vapor-permeable acrylic elastomeric coatings are designed to resist liquid water from outside while allowing water vapor to escape from the wall. However, if the interior side of the wall has moisture drive pushing out, even a permeable coating can trap some moisture. Diagnosing moisture direction is important before coating any wall that shows active water problems.

Elastomeric Coating — Masonry Waterproof Paint Explained

An elastomeric coating is a thick, rubber-like paint or membrane applied to masonry walls that stretches across hairline cracks and forms a continuous waterproof skin to resist water penetration.

Elastomeric Coating diagram — labeled parts and installation context

What It Is

Unlike conventional masonry paint, elastomeric coatings are formulated with acrylic or polyurethane polymers that give the cured film significant elongation — typically 200 to 500 percent stretch before failure. This elasticity allows the coating to bridge hairline cracks up to about 1/16 inch wide as the masonry expands and contracts with temperature and moisture. If a small crack opens slightly during a thermal cycle, the coating stretches across it rather than tearing, maintaining the waterproof barrier.

Elastomeric coatings are applied in thick build coats — usually 10 to 20 mils dry film thickness per coat versus 2 to 4 mils for standard exterior paint. At the recommended two-coat application, the total dry film thickness reaches 20 to 40 mils. The thickness contributes both to crack-bridging ability and to the coating's bulk water resistance. Most products require a primer coat — typically an acrylic block filler or masonry conditioner — on the substrate to improve adhesion and seal high-porosity surfaces. Coverage rates are lower than standard paint, typically 75 to 100 square feet per gallon compared to 350 to 400 square feet per gallon for conventional exterior latex.

Elastomeric coatings are not the same as a waterproofing membrane. They are a surface-applied system that manages incidental water and hairline cracking. They do not substitute for proper drainage, flashing, or control joints in walls that carry significant hydrostatic pressure from below-grade moisture.

Types

Acrylic elastomeric coating is water-based, vapor-permeable, and the most common choice for residential masonry. It allows the wall to breathe — with permeance ratings typically between 8 and 15 perms — while still resisting liquid water on the exterior face. Acrylic formulations clean up with water and produce low VOC emissions, making them suitable for occupied buildings.

Polyurethane elastomeric coating offers higher elongation — often exceeding 600 percent — and better UV resistance, making it well-suited for commercial applications or highly exposed facades that receive intense direct sunlight. Polyurethane coatings are solvent-based and require more careful application and ventilation.

Silicone-modified elastomeric combines silicone water repellency with an elastomeric base for enhanced hydrophobicity. These coatings cause water to bead and run off rather than absorbing into the film surface, extending the time between maintenance cycles in high-rain climates.

Where It Is Used

Elastomeric coatings are applied to exterior brick-veneer, stucco, CMU (concrete masonry unit), split-face block, and poured concrete walls. They are common on older homes with minor surface cracking, on block walls prone to capillary moisture wicking through the masonry, and on stucco that has been repaired but shows fine map cracking. Commercial buildings, parking structures, and institutional facilities use elastomeric coatings on above-grade concrete and masonry walls where appearance and weather resistance are both important.

How to Identify One

An elastomeric coating looks like thick paint with a slightly rubbery or textured surface. The film is visibly thicker than standard paint — running a fingernail across the edge of a chipped area reveals a measurable film buildup. Pressing a fingernail into a coated surface and releasing it will sometimes leave a temporary indent that recovers, unlike rigid paint that would chip or show a permanent mark. The coating may show a slight sheen, a low-sheen texture finish, or a matte appearance depending on the product formulation.

Replacement

Elastomeric coatings typically last 10 to 15 years before chalking, peeling, or losing elongation. Signs of end-of-life include a chalky residue that rubs off on clothing, visible peeling at edges and corners, loss of the rubbery feel when pressed, and hairline cracks in the coating itself that indicate the film can no longer stretch with the substrate.

Recoating requires pressure-washing the surface to remove dirt and chalk, repairing any cracks wider than the coating can bridge with elastomeric caulk or patching compound, applying primer if the old coat is degraded or bare masonry is exposed, and applying two new elastomeric finish coats at the manufacturer's recommended spread rate. Peeling areas must be scraped and sanded smooth before recoating, or the new coat will pull off with the old one. A full recoat on a typical two-story home costs 3 to 6 dollars per square foot applied, including surface preparation.