Acrylic Roof Restoration Coating System Re-Coat Over Acrylic Coated Surface

The Acrylic Roof Restoration Coating System Re-Coat Over Acrylic Coated Surface is a Metacrylics system for a roof that already carries an acrylic coating. It is published as sheet A-08, titled Re-Coat Existing Acrylic Coated Surface, dated 09-25-17, and belongs to the Metacrylics family of commercial roof coating systems.

The Metacrylics Installation Spec Book has a separate re-coat section for existing Metacrylics roofs, with system lives of 5 to 30 years, on pages 44 to 48. The system is one of the acrylic roof coating assemblies in the range and is built from water-based acrylic products only.

The section drawing has an existing acrylic roof surface with Metacrylics acrylic topcoats applied over it. Two alternatives are drawn for the layer between the old coating and the new topcoats.

• Option 1: Acrylic Roof and Tile Primer, with two numbered notes on the sheet.
• Option 2: Acrylic Clear Base.

Roof and Tile Primer is a clear, water-based acrylic primer with penetrating characteristics. Acrylic coated surfaces are among the substrates it is commonly applied over, along with wood, asphalt-based surfaces, concrete, stone, slate, metal, tiles, fiberglass and stucco. It is white in the can and dries clear and not tacky.

• Solids 16-20; pH 7-8; viscosity 1500-6000 cps at 23 degrees C.
• Film elongation at break: 700 percent. Glass transition temperature: 17 degrees C. Water absorption: 5 percent.
• Freeze/thaw stability: not resistant.

It is applied by roller or spray at 0.25 to 1 gallon per 100 sq. ft. and dries in 1 to 4 hours. The roller cover is kept in shade or wrapped between uses. The product is stirred before every application and may be thinned with water if necessary.

Roof and Tile Primer is applied by spray or roll and is supplied in 2-gallon, 5-gallon, 55-gallon and 275-gallon packages.

Metacrylics Clear Base is a transparent, water-based acrylic elastomeric coating. It can be used as a self-priming protective basecoat or as a primer to improve adhesion to existing surfaces. It is white as a liquid, dries clear and tacky, and must be protected from sunlight by an acrylic topcoat. It contains no zinc oxide.

• Temperature cycling and penetration test, 25 continuous cycles from -40 degrees F to 180 degrees F, with 6 inches of water per hour from spray nozzles: pass. Sample thickness changed by less than 1 percent after weathering, and no tearing or cracking was found.
• Tensile strength at 81 mils including 10 mil stitchbonded fabric: 276 psi. Elongation: 434 percent average.
• Hardness: Shore A 41.
• Peel adhesion on concrete: 6.3 lbs per linear inch.
• Water vapor transmission: 0.016 perms (ASTM D1653) at 63 mils dry film.
• Wind uplift 105 PSF; Class A rated for fire under ASTM E-108 and UL Standard 790.

The white topcoat used on re-coat work is Extreme Performance Acrylic White. A quick-set additive premixed by Metacrylics gives rain resistance at 40 degrees F and 80 percent relative humidity within 2 hours or less. The coating weighs 11.3 lbs per gallon and has a VOC content of 27.5 grams per liter. Its Cool Roof Rating Council results (seller ID 0660) are solar reflectance 0.90, thermal emittance 0.88 and SRI 114.

It may be applied as one final topcoat at 1.5 or 2 gallons per 100 sq. ft. depending on the Metacrylics system being applied, because of its dirt resistance and elongation. For a full two-coat spray application the rate is 1.5 gallons per 100 sq. ft. per coat, 3 gallons in all, with 12 to 24 hours between coats. Where the coating is rolled, a full 24 hours or longer separates coats to prevent blistering. It is not applied when rain or freezing weather is expected within 24 hours, in fog or drizzle, or when temperatures are consistently below 40 degrees F. Below 55 degrees F it dries slowly, and 72 hours or more may be needed in shade. It is not thinned.

Details are sealed with Metacrylics Acrylic Gel, an elastomeric mastic for flashing and fabric reinforcement. The gel repairs roof blisters, field seams, drains, scuppers, copings, splits, cracks, fishmouths, and perimeter base and curb flashings. Its 2,000-hour weatherometer test gave no cracking, crazing or erosion and slight chalking. Tensile strength is 156 psi with an elongation of 149 percent average, and it passed low temperature flexibility at 1 inch and -40 degrees F. The gel resists gasoline with some softening and spotting, lubricating oil with some spotting, and 1 percent sodium hydroxide, diesel, 1 percent hydrochloric acid, salt and Stoklard solvent with no effect.