Roof Coatings

Roof Coating Questions, Answered

Which Roof Coating Is Best, What Does It Cost, and How Long Does It Last?

We make these coatings. They've been on commercial, military and residential roofs for over 20 years. Every rep on our support line has put them on a roof. These are our answers, not a reseller's.

What type of roof coating is best?

It depends on the roof. Most guides compare silicone, acrylic and polyurethane, and each gives up something. There is a fourth type that doesn't: epoxy-fortified butyl rubber. That's what ArmorGarage Roof Shield is.

Silicone handles standing water. But it's soft, attracts dirt and can't be recoated.

Acrylic is cheap and reflective. Off-the-shelf acrylics are water-based, so they lose thickness as they cure and chalk away over time. We modify ours with higher solids to avoid both problems, which is how we get a 20-year lifespan.

Polyurethane is hard, but it needs a UV-stable topcoat.

ArmorGarage Tar & Rubber Roof Shield is a high-solids butyl rubber epoxy, not thinned with water. It cures to a thick membrane with 500% elongation and 99.9% memory recovery. It has the lowest permeability rating we've tested against and the highest Shore-D hardness in its class, so it takes foot traffic and hail. And it reactivates, so it can be recoated 15–20 years later.

By roof type: flat tar, modified bitumen and rubber/EPDM roofs → Tar & Rubber Roof Coating. Metal roofs → Metal Roof Coating, a high-solids modified acrylic built for metal's expansion and contraction, in service 20 years and used on every roof at Beale Air Force Base. Low spots that hold water → Ponding Water Roof Coating. Asphalt shingles → Armor Shingle Roof Coating. Spray foam → Foam Roof Coating.

Which is better, silicone or elastomeric roof coating?

For most roofs, neither. Silicone wins on standing water and loses on hardness, dirt pickup and recoatability. Elastomeric acrylic wins on price and loses about a mil of thickness a year to chalking.

Beale Air Force Base ran silicone on its metal roofs. It switched to ArmorGarage Metal Roof Coating for durability and ease of application.

Acrylic elastomerics wear away because they're water-based. Up to half of what's in the pail evaporates during cure, leaving a thin film. ArmorGarage Metal Roof Coating is a modified high-solids industrial acrylic, not water-based. It cures to an extra-thick waterproof membrane, is guaranteed 12 years and routinely lasts 15–20. It also reactivates when recoated, so the new coat bonds to the old. Silicone can't do that.

For tar and rubber roofs the answer isn't silicone or acrylic at all. It's the butyl rubber epoxy above.

What are the downsides of using silicone roof coating?

Silicone is very soft. It tears, scuffs and punctures under foot traffic. Hail, wind-driven debris and ice damage it. It attracts dirt, which kills its reflectivity. It's dangerously slippery when wet. And once it's on the roof, nothing else sticks to it, so recoating means more silicone or a full strip.

Read the warranty before you buy. Silicone warranties typically exclude physical damage and foot traffic. That means the roof you just coated is one you're not supposed to walk on. If your flat roof holds HVAC units, vents or anything a tech has to reach, that's a real limitation.

Those are the exact problems our coatings were built to eliminate. Roof Shield's epoxy polymers give it the highest Shore-D hardness in its class. It takes maintenance foot traffic and golf-ball hail. One customer's 100-year-old metal roof came through a storm that destroyed 80% of the roofs around it with cosmetic damage only. Every ArmorGarage roof coating is recoatable.

Need a walkable area for equipment or a deck? We make a version with rubber granules. Need to handle standing water, the one job silicone is usually chosen for? We make a dedicated ponding water coating. It's recoatable too.

What is the best waterproofing roof coating?

The one with the lowest permeability rating: the tightest chemical structure with the smallest pores, cured into one thick, flexible, seamless membrane. ArmorGarage Roof Shield has the lowest permeability rating of any roof coating we've tested against, and 99.9% memory retention. It won't stay stretched out after years of expansion and contraction the way lower-quality coatings do.

Most roof leaks aren't holes you can see. An aged roof membrane has pores. Cheap coatings start with larger pores, and those pores stretch open further every year from thermal expansion and contraction. Eventually water passes straight through and shows up inside the building somewhere else. That's why finding leaks is so frustrating and costly.

The best coatings start with the smallest pores and a low vapor transmission rating, and don't stretch open with temperature swings. Roof Shield combines a copolymer butyl rubber base (butyl outperforms EPDM, liquid or sheet) with epoxy polymers for hardness. It passed 9,000 hours of ASTM accelerated severe-weather testing.

Silicone is the usual pick for standing water. For those areas we recommend our purpose-built ponding water coating instead.

Are roof coatings a good idea?

Yes, if the roof is structurally sound and dry. A coating restores it for a fraction of the cost of tear-off and replacement, adds 15–20 years of service, and cuts interior heat. It is not a fix for rotted decking, saturated insulation or structural damage.

Two warnings you'll read elsewhere deserve a closer look.

"Coatings peel if the prep is bad." True of every coating. Clean the roof, let it dry out, repair the seams and flashings with our Roof Repair Mastic, then coat.

"Don't coat asphalt shingles." That's advice about elastomeric coatings, which seal the shingle and trap moisture underneath. Our Armor Shingle Roof Coating is breathable. It locks down granules and extends shingle life 7–10 years without sealing the roof assembly.

One example: a large leaking warehouse restored with our coating went from constant leaks to none, and its interior temperature dropped about 7°F.

How many years does roof coating last?

It depends on the quality of the product. Industry averages run 5–10 years for acrylic and 10–15 for polyurethane and silicone. ArmorGarage Tar & Rubber Roof Coating is guaranteed 15 years and routinely lasts 20. Metal Roof Coating is guaranteed 12 years and routinely lasts 15–20. Both recoat for another 15–20.

Three things decide lifespan: cured-film thickness, UV and weather resistance, and whether the membrane recovers its shape after the roof moves.

A water-based coating that goes on at 20 mils and cures to 8 has spent half its life before the first winter. Ours is high-solids. It goes on thick and stays thick, retains 99.9% of its shape after stretching, and was tested to 9,000 hours of ASTM severe weather.

Shingle and foam coatings run shorter cycles, about 7–10 years on shingles, because the substrate itself ages.

How much does it cost to do a roof coating?

Contractor-applied roof coating runs about $1.50–$5.00 per square foot, labor and materials. Doing it yourself with ArmorGarage, materials come to roughly $1.60–$1.95 per square foot for metal, tar and rubber roofs (two coats, free shipping). Ponding-water areas run about $2.35 per square foot on small roofs, and roughly 25% less on large ones. Shingles run about $0.60 per square foot.

If those numbers look higher than the $0.15–$0.50-per-foot pails at the hardware store, that's the point. The cheap end of the range is water that evaporates off the roof, leaving a film that needs redoing in a couple of years. Our per-foot cost buys a full-thickness membrane guaranteed for 12–15 years.

Every ArmorGarage roof coating can be rolled or sprayed by the owner. No crew, no special equipment. Send us photos and square footage and we'll estimate the pails and other materials you need. Roofs over 5,000 sq ft qualify for volume pricing.

How much does a 5 gallon bucket of roof coating cover?

It depends on the coating and the number of coats. Tar & Rubber and Metal Roof Coatings go down at 100 sq ft per gallon. A 5-gallon pail covers 500 sq ft per coat, or 250 sq ft finished at the required two coats. Ponding Water Coating goes on at 50 sq ft per gallon in one coat, so a pail covers 250 sq ft. Armor Shingle Roof Coating covers 1,250 sq ft per pail per coat, or about 625 sq ft finished at two coats.

Those rates build a membrane thick enough to last. That's why they're lower than the 200–400 sq ft per gallon printed on water-based pails. That coverage is thin on purpose.

Order for the finished square footage plus a small buffer for rough or porous surfaces. Add Roof Repair Mastic for seams, flashings and screw heads.

What are people saying about roof coating for shingles?

The common warning is that coating shingles traps moisture and voids the shingle warranty. That warning is about elastomeric and silicone coatings, which seal the shingle surface. A breathable shingle coating does the opposite. It locks down loose granules, seals weathered spots and refreshes color while letting the roof assembly breathe.

Armor Shingle Roof Coating has been one of our best sellers for years for exactly that reason. It extends a serviceable shingle roof 7–10 years, goes on with a roller or garden pump sprayer in a day, and customers report it performs as advertised.

It's for roofs that are aging but sound. It won't rescue shingles that are curling, cracked through or have lost most of their granules. Protect your shingles before they get to that point.

Can a roof coating stop leaks?

Yes. Our coatings are made to stop the leaks you can't find, and the ones you fix that keep coming back. Repair failed seams, loose material, screw heads, damaged flashings and open penetrations with Roof Repair Mastic. Then coat the entire roof. Once it's properly prepped and coated, water can't get through an ArmorGarage roof coating.

Chasing individual leaks is usually futile. Water enters in one place, travels, and shows up somewhere else. You patch, it comes back, and eventually the roof is a pile of incompatible products.

Coating the whole roof solves it once. Over the long run it's far cheaper, and far less stressful, than the patch cycle or constant recoating with cheap products.