Acrylic Roof Restoration Coating System BUR Capsheet

The Acrylic Roof Restoration Coating System BUR Capsheet is the Metacrylics system for existing built-up roofs finished with a cap sheet. It is published as sheet A-01, titled BUR Capsheet Acrylic Restoration Coating System, dated 09-25-17. In the Installation Spec Book the smooth surface BUR and modified cap sheet section carries system lives of 10 to 30 years on pages 11 to 14.

It is a cap sheet roof coating system that offers an asphalt bleed-block primer option.

The section drawing has an existing BUR cap sheet roof with Metacrylics acrylic topcoats over a primer. The primer is drawn as one of two options.

• Option 1: Acrylic Roof and Tile Primer.
• Option 2: Acrylic Bleed Block Primer.

Note 1 seals and reinforces field seams either by 3-coursing with Acrylic Gel and polyester fabric or with Acrylic Base and fabric. Note 2 requires all rooftop penetrations, drains, scuppers, flashing, skylights and perimeter edge flashing to be sealed or reinforced by 3-coursing with Acrylic Gel and polyester fabric. Note 3 states that Acrylic Bleed Block Primer prevents asphalt oils from bleeding through the acrylic and discoloring it.

Acrylic Bleed Blocker Primer is an all-acrylic primer that resists asphalt staining and improves adhesion to the roof substrate. Asphalt substrates can bleed through acrylic and silicone coatings, and the primer is a water-based way to block that bleed-through. It adheres to aged built-up asphalt, modified bitumen, metal, concrete and other substrates, forms a barrier to ultraviolet light, and stays flexible at temperatures as low as 0 degrees C (32 degrees F).

• Appearance: milky white liquid.
• Total solids by weight: 27.5 plus or minus 0.5 percent (ASTM D-2369).
• pH as packed: 9.5 plus or minus 0.3.
• Specific gravity 1.05; density 8.76 lbs per US gallon.
• Tg (DSC): -10 degrees C (14 degrees F).
• Viscosity (Brookfield): 100-400 cps.
• VOC: 37.5 to 50 grams per liter.
• Storage stability: unchanged at 10 days at 60 degrees C. Protect from freezing.

The primer goes on at a minimum of 4 dry mils, about 1 gallon per square, over unaged asphalt. Depending on the condition of the roof, two coats of 8 dry mils each may be needed on unaged asphalt. A wet coat applied over aged asphalt can discolor immediately; the discoloration is water soluble and disappears after a few rainfalls. It is applied by spray, brush or roller and cleaned up with soap and water.

It is not applied below 5 degrees C (40 degrees F), at relative humidity above 90 percent, when rain is expected, or when temperatures are expected to fall below the dew point within the next 6 hours.

The white topcoat is Extreme Performance Acrylic White, with solar reflectance 0.90 and thermal emittance 0.88 (CRRC C-1371), SRI 114 and an initial elongation of 592.63 percent. It is used over BUR asphalt, tar and gravel and granulated cap sheet among other surfaces. A single final coat is 1.5 or 2 gallons per 100 sq. ft. New glazed asphalt and torch-down single-ply assemblies wait 6 months or more before coating.

Acrylic Gel handles the details. It is listed in ICC-ES Report No. 4785, is classified Class A by UL, and has a fire resistance of Class A under ASTM E-108 and UL 790. It repairs roof blisters, field seams, drains, scuppers, copings, splits, cracks and fishmouths. Peel adhesion on concrete is 6.3 lbs per linear inch.