Elastomeric Roof Coating: What It Is and When It's Worth It
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An elastomeric roof coating is a thick, liquid-applied coating that cures into a flexible, continuous membrane over your existing roof. It stretches as the roof heats and cools, sheds water and reflects sunlight. It's worth it when the roof underneath is still dry and sound, often an aging flat or low-slope roof in St. Louis or Kirkwood.
Summer is winding down, and you've now seen how your roof handled a season of heat, pop-up thunderstorms and hail. If a garage roof in Florissant or a flat addition in Kirkwood started leaking at the seams, a coating may buy you years before a tear-off. Or it may be the wrong fix entirely.
What is an elastomeric roof coating?
It's a roof coating with rubber-like elasticity. Once cured, it can stretch with the roof as it expands in the heat and shrinks in the cold, then return to shape without cracking.
It's applied as a liquid, usually in multiple coats, over roofing that's already there: modified bitumen, built-up roofing, roll roofing, metal and some single-ply membranes. Because it goes on as a liquid, it flows over seams, laps and fastener heads and cures as one continuous layer with no seams of its own. It also takes the UV beating that slowly dries out and cracks the roofing underneath.
That's a different animal from paint. Paint is a thin, fairly stiff film meant to color a surface. If the idea sounds familiar from wall coatings, it should, because the principle is the same one behind elastomeric paint coatings on house walls.
What's the difference between acrylic, silicone and other roof coatings?
They're all elastomeric, but they're built on different resins, and each has strengths and weaknesses. In broad strokes, acrylics are the common water-based choice, silicones handle standing water better, and polyurethanes are the tough, abrasion-resistant option.
| Type | Strengths | Watch-outs |
|---|---|---|
| Acrylic | Water-based, easy to work with, good UV resistance, bright white options for reflectivity | Doesn't like water standing on it for long; needs warm, dry weather to cure |
| Silicone | Tolerates ponding water better, very UV resistant | Tends to hold dirt, slick when wet, and generally only silicone sticks to it later |
| Polyurethane | Tough and impact resistant, handles foot traffic, often used as a base coat | Usually solvent-based with more odor; typically priced higher |
The chemistry matters less than the match between product and roof. A coating that's ideal on a well-drained metal shop roof may be the wrong pick for a flat roof that holds water after every storm. ASTM International publishes specifications that liquid-applied roof coatings are tested against, including D6083 for acrylics and D6694 for silicones, so it's fair to ask a contractor which standard their product meets.
Super Shield, the roof system Rhino Shield of Missouri installs, is a ceramic elastomeric roof coating. Our Super Shield roof coating page covers the flat, sloped and white versions.
Can an elastomeric roof coating handle ponding water?
Some can, many can't. Water that's still sitting on a roof a couple of days after the rain stops is the hardest test any coating faces, and it's where coatings fail first.
Standing water keeps the coating wet for long stretches, collects dirt and debris, and in a Missouri winter it freezes and thaws over and over. Acrylics in particular can soften and lose their grip under long-term ponding. Silicones tolerate it better, which is a big part of why they exist.
The better fix is usually to deal with the water. Clear drains and scuppers, add tapered build-up or a small cricket to move water toward the drain, and fix sagging framing that created the low spot. Choosing a coating that tolerates ponding is a backup plan, not a substitute for drainage.
What condition does the existing roof need to be in?
Dry and sound. A coating seals the top of the roof, so anything wet underneath stays wet, and trapped moisture rots decking and ruins insulation from the inside.
Before a coating is even on the table, a good contractor checks for:
- Wet or saturated insulation under the membrane
- Soft or spongy decking
- Blisters, splits and open laps in the existing roofing
- Failed flashing at walls, curbs and penetrations
- Old coatings that are peeling or incompatible with the new product
- Low spots and slow drains
Small problem areas get cut out and repaired. If much of the roof is wet or the deck is going soft, coating it is a waste of your money, and you should hear that plainly.
What does a roof inspection before coating look like?
Expect someone to actually walk the roof, look closely at every edge and penetration, and give you a written scope. A quote written from the driveway isn't an inspection.
- Walk the full roof surface and probe for soft spots
- Check drains, scuppers and gutters, and look for water lines left by ponding
- Inspect flashing where the roof meets walls, chimneys and parapets
- Look at the underside or the ceiling below for staining
- Check how well the existing surface holds a coating, sometimes with a small test patch
- Photograph problem areas and list each repair in the written scope
Late summer is a good time to do this. The season's storms have already shown you where the weak spots are, and there's still a stretch of warm, dry fall weather left for the coating to cure before it gets cold.
When is an elastomeric roof coating worth it?
It's worth it when the roof is dry and structurally sound but the surface is aging, and you want to seal it, cool it and push off replacement. It isn't worth it on a roof that's wet underneath or near the end of its structural life.
Good candidates are aging flat and low-slope roofs with seams starting to open, metal roofs with rust at the screws, and roofs over living space that get too hot in summer. On those, a white coating like our white reflective roof coating also cuts the heat coming through. Poor candidates are roofs with wet insulation, soft decking or chronic ponding nobody plans to fix. Super Shield roof coatings carry a 10–15 year warranty.
Most of what we hear from customers is about the coating on their walls, and the reaction is usually the same surprise at how the product performs. Here's one homeowner:
"Darrin and his team were awesome! The crew that painted was great and the product is better than I expected. Our house looks great."
— Brian C.
He's talking about his home's wall coating, not a roof. The crew that preps and applies it is the same story either way, and on a roof, prep is most of the job.
Frequently Asked Questions
How long does an elastomeric roof coating last?
It depends on the product, the thickness applied, the condition of the roof underneath and how well water drains off it. Super Shield roof coatings from Rhino Shield of Missouri carry a 10–15 year warranty. A coated roof kept in good shape can usually be cleaned and recoated later instead of torn off.
Is acrylic or silicone roof coating better?
Neither is better everywhere. Acrylics are water-based, reflective and well suited to roofs that drain well. Silicones handle standing water better but hold dirt and are hard to recoat with anything else. The right pick depends on your roof's drainage, material and condition.
Can you put an elastomeric coating over a leaking roof?
Only after the leaks are found and repaired, and only if the roof underneath is dry. Coating over wet insulation or soft decking traps the moisture and makes things worse. Small leaks at seams and flashing are commonly repaired as part of the coating prep.
Is elastomeric roof coating the same as elastomeric paint?
They share the same basic idea, a thick, flexible film that moves with the surface, but they're formulated for different jobs. Roof coatings are built to handle direct sun, standing water and foot traffic on a horizontal surface. Wall coatings are made for vertical surfaces like brick, stucco and siding.
See If Your Roof Is a Coating Candidate
We'll walk your roof, check what's under the surface and tell you straight whether a coating, a repair or a new roof makes the most sense. Request a free estimate or call 314-239-7947.
