Elastomeric vs Acrylic Paint on Stucco
By Lemoon's Painting
Elastomeric coating is a thick, stretchy film that can bridge hairline cracks and shed wind-driven rain, while a standard acrylic exterior paint is thinner, breathes more and keeps stucco texture crisp. For most San Diego stucco homes a quality acrylic is the right choice. Elastomeric earns its place on walls with widespread hairline cracking and no moisture coming from behind.
At some point in nearly every stucco repaint, someone mentions elastomeric. It is often presented as the premium option, the one that “waterproofs” the house and “seals the cracks”. Sometimes that is exactly right. Sometimes it is the wrong product for the wall, and the problems it causes show up a few years later as bubbles. Here is how the two really compare.
What is the difference, in plain terms?
Most of both are water-based coatings built on acrylic resins. A standard exterior acrylic paint goes on as a relatively thin film. Elastomeric is formulated to be applied far thicker, often several times the film thickness of ordinary paint, and to stretch and recover as the wall moves. That thickness and stretch are where its strengths and its risks both come from.
What elastomeric does well
It bridges hairline cracks. The fine web of cracking common on older San Diego stucco, the kind that radiates from window corners or covers a sun-baked wall, can be spanned by a thick, flexible film that moves with the wall instead of splitting.
It sheds water from the outside. A continuous, heavy film resists wind-driven rain well. On a wall exposed to winter storms, that can matter.
It hides minor surface wear. The heavier film can even out a weathered surface.
Where elastomeric goes wrong
It usually breathes less. Stucco is a porous material that takes on moisture and gives it back. A standard acrylic allows a good deal of that vapor to escape through the film. Many elastomerics allow less; some newer ones are formulated to let more through, so the product’s data sheet matters. If water gets into the wall from behind (a roof edge, a poorly flashed window, an irrigation head soaking the base of the wall) and the film will not let it out, it cannot leave through the face. It collects behind the coating and pushes it off in blisters.
It holds onto dirt. The film stays soft and slightly tacky in strong sun. On hot inland walls in El Cajon, Santee and Spring Valley, dust sticks to it more than to a harder acrylic film.
It can soften the texture. Applied at the thickness it needs to work, elastomeric fills in some of the detail of a fine sand or lace finish. On a heavily textured wall that hardly shows; on a fine finish it can look plasticky.
It changes the next repaint. Whatever goes over it later has to be compatible with it. That is a manageable step, but it is a commitment.
It uses a lot more material and time. A thick film means more coating per wall and more careful application. That is a cost driver worth knowing about when comparing estimates.
Side by side
| Standard exterior acrylic | Elastomeric | |
|---|---|---|
| Film | Thin to moderate | Thick, high-build |
| Hairline cracks | Will not bridge them for long | Can bridge fine cracks |
| Vapor escape from the wall | Good | Limited |
| Risk if water enters from behind | Lower | Blistering |
| Texture | Stays crisp | Can soften fine textures |
| Dirt pickup in heat | Lower | Higher |
| Next repaint | Straightforward | Must be compatible |
When elastomeric is a good choice
- Stucco with widespread hairline or map cracking, after any larger cracks are repaired.
- Walls exposed to driving rain, where the main threat comes from the outside.
- A wall that has been checked for moisture sources behind it, and none were found.
When a standard acrylic is the better choice
- Any wall with a known or suspected moisture problem from behind.
- Walls with heavy chalking or efflorescence that has not been dealt with at its source.
- Fine-textured stucco where you want the finish to stay sharp.
- Hot, dusty inland exposures where dirt pickup would show.
- Most San Diego stucco homes in reasonable condition, where a quality acrylic from Dunn-Edwards or Sherwin-Williams, over proper preparation, does the job well.
Preparation decides either way
Neither coating fixes what is underneath it. The wall is power washed, chalk is removed, cracks wider than a hairline are opened, filled and textured, loose or hollow stucco is dealt with, and bare patches are primed with a masonry primer suited to the coating. Elastomeric in particular has to go onto a clean, sound, dry surface, or its thickness only means a thicker layer of failure. How stucco cracks are repaired before painting.
Getting the choice right
The useful question is not “which coating is better” but “what is this wall doing”. A good painter checks where water could be getting in, how the stucco is cracking and how much sun the wall takes before recommending either one.
Ebenezer will look at your elevations and tell you which coating fits each one, and why, before you decide. Sometimes the answer is acrylic on the house and something heavier on one exposed wall. More on exterior painting and waterproofing, or on stucco homes in Chula Vista and Spring Valley.
Wondering whether elastomeric is right for your walls? Ask for a free estimate and get an answer based on your house rather than a sales pitch.
Common questions
Does elastomeric paint make stucco waterproof?
It makes the face of the wall much more resistant to rain, because the film is thick and continuous. It does not stop water that gets in from behind, through a roof leak, a window flashing or a sprinkler soaking the base of the wall. Water trapped behind a thick film is what causes elastomeric to blister.
Will elastomeric coating fix my stucco cracks?
It can bridge fine hairline cracks and keep them from showing for longer than ordinary paint. It does not fix cracks that are wider, that keep moving, or where stucco has come loose. Those still need to be opened, filled and textured before any coating goes on, elastomeric or not.
Can I go back to regular paint after elastomeric?
Yes, but with care. A later coat has to be compatible with the elastomeric film and applied over a clean, sound surface. Some products bond well to elastomeric and some do not, so the label matters. It is one more reason to choose elastomeric deliberately rather than by default.
Why does elastomeric sometimes look dirty sooner?
Elastomeric films are soft and slightly flexible, and in strong sun they can soften further. Dust and pollen stick to that surface more readily than to a harder acrylic film. On a hot inland wall that can mean a dingier look sooner, which is part of why it is not the automatic choice in El Cajon or Santee.