Why Elastomeric Is the Right Call for Stucco and EIFS Buildings in BC

If you manage a stucco or EIFS-clad commercial building in Burnaby or anywhere in Metro Vancouver, you've probably seen the same failure pattern: paint that looks fine in year one, develops hairline cracks in year two, starts lifting at window perimeters and control joints in year three, and is peeling badly by year five. Then comes the call to repaint. The cause, almost every time, is the wrong coating specification for the substrate and the climate.

What Standard Exterior Latex Can't Do

Standard 100% acrylic exterior latex is a good product for many applications. On wood siding, it provides excellent adhesion and moisture resistance. On metal, with the right primer, it performs well. On stucco and EIFS in a BC coastal climate, it has a fundamental limitation: it doesn't move with the substrate.

Stucco and EIFS expand and contract with temperature changes. The stucco system on a south-facing wall in Burnaby might see surface temperatures ranging from -5°C in January to 55°C on a sunny July afternoon — a 60°C range. Standard latex has an elongation at break of around 50–100%. When the substrate moves outside that range, the paint cracks. Once it cracks, water gets in, freeze-thaw cycles make the cracks bigger, and the coating fails progressively.

How Elastomeric Coatings Work Differently

Elastomeric exterior coatings are formulated with a significantly higher rubber-like polymer content than standard latex. This gives them an elongation rate of 150–400% — meaning the cured film can stretch to four times its original length and return to its original dimensions without cracking. Applied at the correct wet-film thickness (typically 10–20 mils wet, yielding 5–10 mils DFT, versus 3–4 mils for standard latex), an elastomeric coating forms a continuous flexible membrane over the stucco surface rather than a rigid film.

The practical result: the coating bridges hairline cracks as they open and close with temperature cycling, rather than cracking through them. It also forms a Class A breathable waterproof membrane — water vapour from inside the building can pass outward through the film, but bulk liquid water can't penetrate inward. This is the correct behaviour for a stucco or EIFS exterior in a wet climate: breathable from inside, waterproof from outside.

The Products We Use

The primary elastomeric systems we specify for BC commercial exteriors are: Benjamin Moore MoorElastic (a water-based 100% acrylic elastomeric available in flat and low-sheen finishes), Sherwin-Williams Loxon Elastomeric (a leading commercial specification product in Western Canada), and ICI Dulux Weathershield Elastomeric (a strong performer on stucco in high-moisture exposure zones). All three are specified at 1.0–1.5 mils wet per coat with two coats minimum, over an elastomeric primer on prepared stucco surfaces.

The Cost Question

Elastomeric products cost roughly 20–40% more per litre than premium exterior latex, and they apply at lower coverage rates (due to higher application thickness), so the material cost per square foot is meaningfully higher. On a straightforward 3,000 sq ft stucco exterior, the product premium might add $800–1,500 to the total cost. Against a five- to ten-year performance advantage over standard latex on BC stucco — and the cost of a full repaint cycle that standard latex will require in five years rather than ten — the elastomeric specification is the correct economic choice on most BC commercial buildings. We make this recommendation on every stucco and EIFS exterior we quote, and we explain the reasoning.

Written by the Burnaby Commercial Painting Co Team. Related: Commercial Exterior Painting · Specialty Coatings