Best Roof Sealants and Coatings of 2026: Reviews by Category

Walk into a roofing supply house or a big-box store and the sealant and coating aisle can be genuinely overwhelming. Dozens of products make claims like “stops leaks instantly,” “bonds to anything,” and “lasts 20 years.” Some deliver on those claims. Many don’t — or they deliver in very specific applications that may not match your roof.

The right sealant or coating depends entirely on what you’re trying to accomplish: sealing a flashing joint, waterproofing an entire low-slope membrane, protecting an aging asphalt cap sheet, or coating a metal roof to add reflectivity. Different problems require different chemistries.

This guide organizes the best products by category, covering what each type is best for, how to apply it, typical coverage rates, and price ranges.

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Category 1: Asphalt Roof Cement (Plastic Cement)

Asphalt roof cement — also called plastic cement, flashing cement, or “tar in a can” — is the oldest and most widely available roof repair product. It’s a thick, fibered asphalt compound used for sealing laps, embedding flashing, and making spot repairs on asphalt shingle or cap sheet roofs.

Best for: Spot repairs on asphalt roofs, bedding flashing, sealing shingle laps, patching holes or torn sections in asphalt cap sheets. Not for use on non-asphalt surfaces.

Not for: Long-term exposed applications — asphalt cement oxidizes and cracks when exposed to UV over time. It should always be covered by shingles or mineral-surface material.

Gardner Leak Stopper Roof Patch

Gardner’s plastic cement is one of the most widely available products in this category. It comes in quart, gallon, and 5-gallon pail sizes and is available at virtually every hardware store. The fibered formula provides good body for gap-filling applications.

• Coverage: Approximately 25–30 sq ft per gallon at 1/8” thickness
• Price: ~$12–$18 per gallon
• Application: Trowel, putty knife, or caulk gun (tube version)
• Best use case: Bedding step flashing, sealing lifted shingle edges, patching minor holes in cap sheet

Karnak 19 AF Fibrated Asphalt Roof Cement

Karnak is a professional-grade brand with a stronger following in the trade than at retail. The 19 AF is a fibered asphalt cement that performs very similarly to Gardner but with slightly better consistency and fewer voids in the fibered matrix.

• Coverage: 25–30 sq ft per gallon
• Price: ~$18–$25 per gallon
• Application: Trowel; this is a thicker formula better suited to trowel than caulk gun application
• Best use case: Flashing bedding, large-area patching on flat roofs, embedding fabric for roof patches

Bottom line on asphalt cement: These products work for their intended applications when used correctly. The common failure mode is using them as a “fix everything” solution — particularly applying them over flashing joints where proper mechanical repair is needed, or leaving them exposed to UV. Use asphalt cement as a component of a proper repair, not as the repair itself.

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Category 2: Elastomeric Roof Coatings

Elastomeric coatings are thick, rubber-like liquid coatings that dry to form a flexible, waterproof membrane over an existing roof surface. They are primarily applied to low-slope roofs — flat roofs, low-pitch commercial roofs, and cap-sheet systems — as a restoration and waterproofing treatment.

Best for: Extending the life of aging flat and low-slope roofs, waterproofing cap sheet systems, metal roofs, and built-up roofs. Also used on RV roofs and low-slope residential additions.

Not for: Steep-slope (shingled) roofs where the coating would be visible and would not adhere properly to asphalt shingles.

Henry 587 Ultra White Roof Coating

Henry is one of the most recognized names in commercial and residential flat-roof coatings. The 587 is a water-based elastomeric coating that applies well with a roller or brush, dries white (improving roof reflectivity), and stretches with the roof substrate through thermal cycling.

• Coverage: 1.5–2 gallons per 100 sq ft (per coat; two coats typically recommended)
• Price: ~$35–$45 per gallon
• Application: Roller, brush, or airless sprayer
• VOC status: Low-VOC, water-based — suitable for use in regulated states
• Best use case: Restoration coating on aging cap sheet or single-ply roofs; excellent reflectivity for energy savings

Rust-Oleum 301903 Elastomeric Roof Coating

Rust-Oleum’s elastomeric coating is more widely available at retail (Home Depot) than Henry and offers broadly similar performance at a slightly lower price point. It’s a good choice for DIY homeowners with low-slope additions or mobile homes.

• Coverage: 100 sq ft per gallon (approximately)
• Price: ~$28–$38 per gallon
• Application: Roller or brush
• Best use case: Residential flat roofs, low-slope additions, mobile home roofs

Key application note for all elastomeric coatings: Surface preparation is critical. The roof must be clean, dry, and free of loose material. Applying an elastomeric coating over a dirty or wet surface dramatically reduces adhesion and lifespan. Most manufacturers recommend a primer coat on highly porous substrates.

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Category 3: Silicone Roof Coatings

Silicone coatings represent the premium tier of liquid-applied roof restoration products. Unlike acrylic-based elastomeric coatings, silicone does not re-emulsify when wet — which makes it uniquely resistant to ponding water, the most destructive condition a flat roof faces.

Best for: Low-slope roofs where water ponds after rain, SPF (spray polyurethane foam) roofs, metal roofs, and any application where long-term UV resistance is critical.

Not for: Situations where future re-coating with a different product is anticipated — silicone is notoriously difficult to topcoat with anything other than more silicone.

GacoFlex S20 Silicone Roof Coating

GacoFlex (now owned by Firestone Building Products) is the most widely used silicone roof coating in the market. It comes in multiple colors (white, gray, tan) and is available in 1-gallon, 5-gallon, and 55-gallon drum sizes. The S20 is specifically formulated for roofing applications.

• Coverage: 1.5–2 gallons per 100 sq ft for a 20-mil DFT (dry film thickness) — the minimum for a warranted application
• Price: ~$55–$75 per gallon
• Warranty: Gaco offers contractor-applied warranties up to 20 years
• Application: Airless sprayer is recommended for large areas; roller for small areas
• Ponding water resistance: Yes — rated for indefinite ponding water exposure
• Best use case: Commercial and residential flat roofs with drainage issues; SPF restoration; metal roof coating

Duro-Last Duro-Shield 10 Year Silicone Coating

Duro-Last’s silicone coating system is aimed at extending the life of existing single-ply or built-up roof systems under a contractor-backed warranty program. Less widely available for DIY purchase but worth specifying for commercial restoration projects.

• Coverage: Similar to GacoFlex at 20+ mil DFT
• Price: ~$60–$80 per gallon
• Best use case: Commercial flat roofs as part of a warranted restoration system

Bottom line on silicone: If your flat roof ponds water or if long-term UV resistance is the priority, silicone is worth the premium over acrylic elastomeric products. The inability to topcoat with non-silicone products is a long-term commitment — the roof will need silicone indefinitely going forward.

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Category 4: EPDM and Liquid Rubber Sealants

EPDM (ethylene propylene diene monomer) rubber is a synthetic rubber membrane widely used as a roofing material itself, but liquid rubber formulations provide a brush-on alternative for coating, repairing, and extending the life of EPDM roofs as well as other substrates.

Liquid Rubber Waterproof Sealant/Coating

Liquid Rubber is a solvent-free, water-based product that cures to form a seamless rubber membrane. It bonds to EPDM, TPO, metal, concrete, wood, and most roofing substrates.

• Coverage: 40–60 sq ft per gallon for a 20-mil membrane (thicker is better for waterproofing; 3+ coats for full membrane applications)
• Price: ~$45–$65 per gallon
• Application: Brush, roller, or squeegee; self-levels to some extent
• Best use case: EPDM repair and restoration, RV roofs, flat roof seams, around penetrations and drains
• VOC: Zero VOC — one of the most environmentally friendly coating options

Key advantage: Liquid Rubber can be applied in a single-component brushable form without specialized equipment, making it practical for homeowners and contractors alike. For full-roof applications, coverage rates make it more expensive per square foot than elastomeric coatings — but for detail work around drains, seams, and penetrations, nothing applies more easily.

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Category 5: Flashing and Joint Sealants (Roofing Caulks)

Flashing sealants are a distinct category from coating products — these are typically single or two-component polyurethane, modified silicone, or butyl-based compounds designed to seal metal-to-masonry, metal-to-metal, and metal-to-roofing joints. They need to be flexible, paintable (in some cases), and have excellent adhesion to both metal and masonry surfaces.

Best for: Counter flashing-to-masonry joints, cap flashing seams, around penetrations, at skylights, and anywhere a flexible, adhesive sealant is needed in a roofing joint.

NP-1 Polyurethane Sealant (Pecora)

NP-1 is a professional-grade, one-component polyurethane sealant widely used in commercial and high-end residential roofing. It cures to a rubber-like consistency, bonds aggressively to masonry, metal, and wood, and can be painted once cured.

• Coverage: Linear foot coverage depends on joint width; a 10 fl oz cartridge will fill approximately 30–50 linear feet of 1/4” x 1/4” joint
• Price: ~$12–$18 per cartridge
• Cure time: 7–14 days to full cure
• Best use case: Counter flashing-to-chimney joints, cap flashing seams, any masonry-metal joint

Geocel 2300 Tripolymer Roof Sealant

Geocel 2300 is perhaps the most widely recommended product among roofing professionals for general-purpose flashing and joint sealing. It adheres to virtually every roofing substrate, remains flexible through wide temperature ranges, and can be applied in cold weather (down to 0°F).

• Coverage: Approximately 25–40 linear feet per cartridge at 1/4” joint width
• Price: ~$10–$15 per cartridge
• Temperature range: -80°F to 300°F (excellent for both cold climates and metal roofs in hot climates)
• Best use case: Step flashing seals, pitch pans around penetrations, general metal-to-roofing joints, RV roof seams

Henry 208R Rubberized Flashing Cement

For applications requiring a trowel-grade sealant rather than a caulk-consistency product — particularly for embedding base flashing at chimney bases — Henry’s 208R is a rubberized, non-fibered asphalt cement with good adhesion and flexibility.

• Coverage: 25–30 sq ft per gallon
• Price: ~$20–$28 per gallon
• Best use case: Embedding and sealing base flashing, sealing around chimney bases

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Choosing the Right Product: Quick Reference

Application	Best Product Type	Top Picks
Flat roof restoration (no ponding)	Elastomeric coating	Henry 587, Rust-Oleum Elastomeric
Flat roof with ponding water	Silicone coating	GacoFlex S20
EPDM repair/restoration	Liquid rubber	Liquid Rubber Waterproof Sealant
Flashing joint sealing	Polyurethane sealant	Geocel 2300, NP-1
Masonry-to-metal joint	Polyurethane sealant	NP-1, Geocel 2300
Spot repair on asphalt shingles	Asphalt roof cement	Gardner, Karnak 19 AF
Embedding base flashing	Rubberized cement	Henry 208R
Around penetrations (detail work)	Liquid rubber or polyurethane	Liquid Rubber, Geocel

The single most common mistake when selecting roof sealants is using asphalt cement for everything. It is appropriate for asphalt-to-asphalt applications when covered, and not much else. For flashing joints, use a dedicated polyurethane or tripolymer sealant. For flat roof restoration, use a coating product appropriate for your specific roof type and drainage conditions.

When in doubt, read the technical data sheet — not just the label — before purchasing. Most manufacturers publish detailed substrate compatibility information, coverage rates, and application conditions that the packaging doesn’t have space for.