As you stand back and admire your metal roof, you can't help but feel a sense of pride. The sleek lines, the durable material and the promise of a long-lasting roof fill you with satisfaction. But as a savvy homeowner, you know the job isn't done just yet.
A metal roof is sturdy and resilient, but it still needs a protective layer to shield it from the elements and keep it going for the long haul. That's where metal roof sealant comes in. This guide covers how to seal a metal roof from start to finish: why it matters, which sealant to use, how to find leaks and how to apply it yourself.
Why Seal a Metal Roof?
Metal roofs are tough. Most are made from steel, aluminum, copper or zinc, and they're installed as standing seam panels, corrugated panels or metal shingles. But tough doesn't mean leak-proof. Metal roofs are vulnerable to rust and corrosion, and water will find any gap it can.
Even with metal's resistance to water, you're going to want to seal problem areas like the sidewall flashing, contact points and the edges.
With high-sloped roofs, for example, gravity carries the water down the eaves of each panel, siphoning it to the next panel underneath. But with lower-sloped roofing, sealant will be necessary in between each panel to prevent water from getting in. For that matter, any area where water can get through needs to be properly sealed, including points of contact between panels as well as the flashing.
Benefits of Using Sealant for Metal Roofs
Sealing your metal roof does more than stop the drip. Here's what you get.
Stops Leaks and Water Damage
Sealant creates a barrier that keeps water from seeping through seams, joints and other weak spots. That matters, because leaks can lead to mold, structural damage and even electrical problems if they're not caught early.
Protects Against Rust and Corrosion
Metal roofs, especially steel ones, can rust when they're exposed to moisture for long periods. High humidity and salt air make it worse. Sealant keeps moisture from reaching the metal, which helps slow corrosion and protect the structure of your roof.
Refreshes the Look of Your Roof
Over time, metal roofs can get stained, discolored or dull. A fresh coat of sealant revives the look of an older roof. Go with a colored sealant and you can match or change the look of your home.
Costs Less Than Replacing Your Roof
Sealing your roof costs a lot less than replacing it. It helps extend the life of your roof and cuts down on repairs. And since anyone with basic DIY skills can apply it, you save on labor too. No contractor needed.
The Right Sealant for Metal Roofs
To get a well-sealed, weatherproof roof, you're going to want a sealant specifically designed for metal roofs. A good sealant for metal roofs should have:
- Strong adhesion, so it bonds tightly to the metal and leaves no gaps for water
- Flexibility, so it moves with the metal as it expands and contracts with temperature changes, without cracking or peeling
- Durability, so it holds up to heavy rain, snow and high winds
- Easy application, so you can get the job done with a brush, roller or sprayer
Liquid Rubber offers a range of waterproof sealants, but for metal roofs, MetalSafe Sealant or Color Roof Sealant is the top choice. Both form a flexible, waterproof membrane that protects against rust and leaks, which can otherwise lead to water damage in the supporting structures of your roof. Which one you pick depends on what your roof needs most.
MetalSafe Sealant for Rusty Metal Roofs
If your roof already shows signs of rust, MetalSafe Sealant is the one to reach for. It's a bitumen-based sealant with built-in rust inhibitors that help slow and prevent further corrosion while sealing out water. It goes right over light surface rust with no primer needed, and it bonds to galvanized steel, aluminum and copper. It dries black.
Color Roof Sealant for Color and Curb Appeal
Sometimes appearance matters just as much as waterproofing. Color Roof Sealant is an acrylic hybrid sealant that comes in nine color options, including clear. Clear is handy when you want protection without changing how your roof looks. It contains no solvents, it's non-flammable and it's not affected by sunlight.
Pick one or the other. Don't apply Color Roof Sealant over MetalSafe Sealant.
How to Find Leaks on a Metal Roof
You're going to want to inspect your metal roof for leaks before you apply the sealant. Look for water staining, which helps you spot trouble areas, and make sure the roof drains properly. Check carefully around vents, rooftop units, skylights and solar panels. Here are some other signs to look out for:
- Loose or missing fasteners
- Damaged panels
- An open headwall or flashing
- Missing trim
- Loose gutters and downspouts
- Gaps in seams
- Rust damage and holes
- Worn-out butyl strips or old sealant
- Tighten, repair or replace loose screws, damaged panels and worn-out sealant before you go any further.
If you find any of these signs, it's time to seal your roof.
Check Your Butyl Sealant Strips
Butyl sealant is a sticky, rubbery sealant that stays soft instead of hardening. On many metal roofs, it's installed as strips or tape between overlapping panels and along seams, flashing, trim and ridge caps when the roof is built. Over time, especially with sun exposure, butyl can dry out, crack or pull away. That leaves a path for water. If your butyl strips look dried out, cracked or loose, repair or replace them before you seal.
How to Seal a Metal Roof, Step by Step
Sealing a metal roof is a beginner-friendly project. If you can roll on paint, you can do this. Here's how.
Step 1: Clean and Prep the Roof
Sealant needs a clean, dry, solid surface to bond to. Before you start:
- Inspect any fasteners and repair or replace them as needed.
- Remove any cracked or peeling silicone caulking.
- Remove heavy rust and scale.
- Clean off tougher contaminants with Multipurpose Cleaner. Wet the surface lightly, apply the cleaner, let it sit for 5 to 10 minutes without drying, scrub with a stiff bristle brush and rinse with clean water.
- Pressure wash your roof.
- Tape off any areas you don't want coated.
Step 2: Let It Dry
Allow your roof to dry thoroughly after pressure washing.
Step 3: Fill Screw Holes and Small Cracks
Fill screw holes, cracks and joints between 1/8 and 1/2 inch with Sealant & Adhesive Caulk. Smooth the material after you apply it, then let it cure for 24 hours.
Step 4: Treat Rust Spots
If you're using Color Roof Sealant, apply a water-based rust primer or converter over any rust spots. MetalSafe Sealant doesn't need a primer over light surface rust.
Step 5: Bridge Seams, Vents and Flashing
Bridge all seams, joints and cracks with Seam Tape, including around vents, flashing and other protrusions. It's a peel-and-stick tape that makes those areas watertight before you coat, so your sealant isn't the only thing keeping water out.
Step 6: Apply the Sealant
Start in the farthest corner and work toward your exit in manageable sections, about 10 ft x 10 ft at a time. Use a brush, roller or sprayer. Keep a wet edge as you go, and when you lap onto a dry section, overlap by 4 to 6 inches. Coat right over the Seam Tape around vents, flashing and protrusions. Check each coat for blisters or pinholes and fix them as you go. Pull your masking tape while the coating is still wet.
Let each coat dry 6 to 8 hours before you apply the next one. Apply each new coat in the opposite direction of the last one, and put your final coat on in the direction of the slope so water drains properly.
So how many coats do you need? That depends on you. Everyone applies coats at a different thickness. Go thin and you'll do more coats. Go thick and you'll do fewer. That's why we don't count coats. Instead, get the full amount of sealant your project calls for. Apply a coat, let it dry, apply the next one and keep going until the sealant's gone. Both MetalSafe Sealant and Color Roof Sealant cover 30 sq ft per gallon total, not per coat. If you've calculated your coverage, you'll end up with the right thickness.
On roofs with more of a slope, stick with thinner coats so the sealant doesn't drip while it dries.
Step 7: Let It Cure
Allow the sealant to cure completely. That takes 48 to 72 hours, depending on humidity.
Choosing the Right Time to Apply the Sealant
The best time to apply your metal roof sealant is when you can avoid direct sunlight and the air, surface and overnight temperatures stay between 50°F and 86°F (10°C and 30°C). A few more things to check:
- No rain in the forecast for 24 hours
- Humidity below 80%
- The roof surface is at least 5 degrees above the dew point
Generally speaking, it's best to start earlier in the day. You'll want 6 to 8 hours of dry time before fog or dew sets in, plus ample time for drying between coats.
How to Maintain a Sealed Metal Roof
Once your roof is sealed, a little upkeep keeps it that way. Inspect it once or twice a year for blistering, peeling or cracks, especially around seams and penetrations. After winter is the best time. If you spot damage, fix it sooner rather than later.
To clean your roof, sweep off any loose debris, then use Multipurpose Cleaner the same way you did during prep. Plan on a refresher coat in about 5 years.
One more thing: a sealed roof isn't meant to be walked on regularly, so keep foot traffic to a minimum.
Wrapping Things Up
When it comes to sealing and protecting your metal roof, Liquid Rubber has you covered. MetalSafe Sealant takes on rust. Color Roof Sealant gives you the look you want. Both protect your roof from the elements and revive the look of an older roof, which adds to your home's curb appeal. They're cost-effective, reliable and easy to apply, which makes them a great fit for DIYers. Ready to get started? Use our Metal Roof Kit Builder to get the right amount of everything for your project. Have a question first? Reach out to our Product and Application Support Team through our Contact Us page. They can walk you through the whole process.
Metal Roof Sealant FAQs
Can I seal a metal roof myself?
Yes. Sealing a metal roof is a beginner-level project. You can apply MetalSafe Sealant or Color Roof Sealant with a brush, roller or sprayer, and you don't need any special skills or training.
How much sealant do I need?
Both MetalSafe Sealant and Color Roof Sealant cover 30 sq ft per gallon. That's the total amount you need, not per coat, so a 5-gallon pail covers 150 sq ft. Our Metal Roof Kit Builder will calculate how much you need for your roof.
When it comes to questioning how many coats you need, think of it like this: you buy the amount of product you need as recommended by the Kit Builder. Apply a coat, then let it dry, and continue applying coats until you've used all the product.
We don't share a "recommended number of coats" because everyone seems to apply coats with a different thickness, so we could say "2 coats" and then if you spread 2 thin coats, you might not have put down enough to achieve the proper coverage.
Can I use MetalSafe Sealant and Color Roof Sealant together?
No. Choose one or the other. Don't apply Color Roof Sealant over MetalSafe Sealant, and don't combine the two.
Is roof sealant a replacement for a new roof?
No. Liquid Rubber is a restoration product. It's made to seal and protect the roof you already have. If you're coating a roof over a living space, check your local building code first, since it'll usually require approved roofing, waterproofing and cladding materials.
