Mastic Primer 101

For use on porous roof substrates. This elastomeric primer is designed to penetrate the roof substrate and create a perfect bonding surface for the top coat. Designed as primer ONLY.

SKU: 101 Categories: , ,

If you need to order quantities of 50 gallons or more, please call us at 800-275-5628 for the best price and to save on shipping.

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Mastic Primer 101 (Roof Primer) is a water-based, elastomeric coating and sealant made from 100% acrylic resins. This extremely durable, penetrating sealant is tenacious and is designed to be used as a prep and prime coat and/or to restore coarse or highly weathered surfaces. The product is made with mildew resistant agents and is highly resistant to the sun’s ultraviolet rays. Mastic Primer 101 is a permanently flexible, breathing membrane, allowing moisture from the substrate or building interior to escape while remaining impervious to water penetration from the exterior. Mastic Primer 101 is not intended to be used as a primer coat on rusted metal roof surfaces – see Metal-Koat 102 Rust Inhibitive. This product is designed as a low hide base or primer coat only.



Mastic Primer 101 (Roof Primer) is engineered and developed to perform well under severe commercial, residential, industrial, agricultural and institutional applications. Use on asphalt, fiberglass or asbestos shingles, barrel, concrete or clay tile, roll roofing, B.U.R. roofs, polyurethane foam, and single ply roofing (EDPM, TPO, PVC).

Product Data

Vehicle: 100% Acrylic Resin
Solvent: Water
Flash Point: None
Drying Time: 4 hour to touch (77°F & 50% relative humidity) 12 hours to re-coat
Weight per Gallon: 8.6 lbs
Solids-Weight: 32%
Solids-Volume: 30%
Colors: White
V.O.C.: 0.19lbs/gal


Environmentally Friendly
Keep Out of Reach of Children
Product will freeze below 32°F (0°C)


Surface must be clean, dry and free of dirt, grease and mildew. Remove any trace of mildew by washing with a solution that kills mildew spores. Old coating or residue that is loose or peeling must be removed by scraping, sanding, wire brushing or pressure washing. Avoid using cleaners with built-in wax or silicone additives since this may affect coating bond. Make any necessary repairs or replacements to damaged or leaking roof material. Rusty metal surfaces should be primed with the proper material, see Metal-Koat 102, Rust Inhibitive. If repairs are needed, please refer to “Go Green Roof Repair”.

IMPORTANT: Where ponding water conditions persist beyond 48 hours, roof drains or other corrective measures must be installed to eliminate water build-up prior to coating the roof. 


This product is designed as a top or finish coat (see Thermo-Flex 103 or Metal-Koat 102). Maximum adhesion and durability is achieved only when the surface is clean, dry and properly prepared. Slope for positive drainage is recommended for any roofing application. Highly weathered surfaces may require additional coverage. A continuous film should be applied, making sure all surfaces are uniformly coated and free from voids, pinholes and blisters. Apply with a brush, roller (1 1/4″ Nap) or spray equipment (Airless Sprayer – flow output 1.2 gpm, minimum pressure 2000 psi, tip size .0517). Drying time is retarded by very high humidity. Do not apply at temperatures below 50°F. Do not apply when rain is eminent. 


Clean brushes, rollers, spray and other equipment immediately after use with hot soapy water.