Elastomeric Paint vs. Exterior Latex: Which One Belongs on Your House?

Elastomeric paint is a thick, rubbery acrylic that goes on many times heavier than standard exterior latex and stretches to bridge hairline cracks. It's the better choice on stucco, block and other masonry. Standard exterior latex is thinner, breathes more easily, and is usually the safer pick for wood siding. Ceramic elastomeric coatings are a third, system-based option.

We get this question a lot in July, when homeowners around St. Louis and St. Charles are looking at sun-baked walls and wondering whether the next finish should be something heavier. The answer depends mostly on what your house is made of. Here's how the two compare, and where each one goes wrong.

What is the difference between elastomeric paint and exterior latex?

Both are water-based acrylics. The difference is how much solid material ends up on the wall and how far that film can stretch. Elastomeric paint is formulated to build a very thick, flexible film. Exterior latex builds a thin, harder one.

A conventional exterior paint job typically leaves a dry film of about 1 to 2 mils. Elastomeric products are applied far heavier, often several times that thickness, and the cured film can stretch and recover as the wall expands and contracts. That's what lets it span fine cracks instead of splitting along them.

When is elastomeric paint the right choice?

Use it on masonry surfaces that crack and let water in. Stucco, concrete block and tilt-up concrete are the classic cases, especially walls with a network of fine shrinkage cracks that keep reopening after each Missouri freeze-thaw season.

On those walls, a thin latex film just follows the crack and splits. A heavy elastomeric film can span it. It also sheds driving rain well, which helps on exposed west and south walls that take the worst of our summer storms. If you're comparing specific products, the Master Painters Institute keeps standards and approved product lists by category, elastomeric included.

Where is elastomeric paint the wrong choice?

It's often the wrong pick for wood siding and for any wall with an active moisture problem. Because the film is so thick and tight, many elastomeric masonry paints slow the movement of water vapor. If moisture gets into the wall from inside the house or from behind the siding, it can't escape easily.

On wood that leads to blistering, peeling and, worse, rot under a finish that still looks fine from the street. Plenty of paint manufacturers specifically say their elastomeric masonry products aren't for wood siding. Read the label.

Other situations where it causes trouble:

• Structural cracks. Elastomeric bridges hairline cracks. It won't hold a wall together that's still moving.
• Thin application. Rolled on like regular paint, it loses most of what makes it elastomeric.
• Hot, sunny walls. Some elastomerics stay a little soft in high heat and can pick up dirt.
• Poor prep. Chalky or dirty surfaces need cleaning and the right primer, or the heavy film won't stay put.

Timing matters in summer, too. Heavy-bodied coatings need time to cure, and applying them on a scorching wall in direct afternoon sun can cause problems. Good crews follow the sun around the house and watch the forecast for pop-up storms.

Is standard exterior latex good enough?

For a lot of houses, yes. A quality acrylic latex on sound wood, fiber cement or previously painted siding performs well when the prep is done right. It's the lower-cost option, it's easy to touch up, and it lets the siding dry out.

The limit is lifespan. A 1 to 2 mil film exposed to Missouri UV, humidity and hail breaks down, and most homeowners end up repainting every 5 to 7 years. Our guide to the best exterior paints goes through what to look for in a latex finish if that's the route you choose.

How is a ceramic elastomeric coating different?

A ceramic elastomeric coating is installed as a complete system, with prep and primer matched to each surface, rather than one heavy product rolled on everything. Rhino Shield uses ceramic microspheres in a specialized resin, goes on at 8 to 10 mils, and is backed by a 25-year transferable warranty.

The ceramic content is the difference you'll notice over time. It reflects UV, which helps color resist fading on sunny walls, and the coating is formulated to resist mold and mildew. Rhino Shield of Missouri applies it to brick, block, stucco and metal, and also to wood, cedar and fiber cement siding, using a prep sequence suited to each. We wrote about the general category in our earlier post on elastomeric paint coatings.

It costs about 2 to 2.5 times a traditional paint job up front. Whether that makes sense comes down to how long you're staying and how many repaint cycles you'd skip. On wood, ask any contractor proposing a heavy coating, including us, how their system handles moisture in the siding. You want a specific answer.

Clear answers are what most homeowners are after when they compare quotes. One customer told us what mattered to him:

That's the standard to hold any contractor to, whether they're quoting latex, elastomeric or a full exterior coating system.

Frequently Asked Questions

Can you put elastomeric paint over latex paint?

Often, yes, if the existing latex is well bonded, clean and not chalking. Loose or peeling paint has to come off first, and some products call for a primer. The bigger question is whether the surface underneath is one elastomeric suits, such as stucco or masonry rather than wood siding.

Can you use elastomeric paint on wood siding?

Most elastomeric masonry paints aren't recommended for wood siding because they can trap moisture and lead to blistering or rot. Check the manufacturer's label. Coating systems built for wood use their own prep and primer, so ask the contractor how their system handles moisture in wood.

How long does elastomeric paint last?

It varies a lot with the product, film thickness and prep. A properly applied elastomeric on masonry generally outlasts standard latex, but a thin coat over a dirty wall won't. Look at the manufacturer's warranty terms and the contractor's written scope for real numbers.

Is elastomeric paint waterproof?

It's highly water-resistant and sheds driving rain well, which is why it's popular on stucco and block. It isn't a fix for leaks from failed flashing, gutters or structural cracks. Those need repair before any coating goes on.

Not sure which finish fits your house?

We'll look at your siding and tell you what we'd put on it, and why. Request a free estimate or call 314-239-7947.