Acrylic Roof Restoration Coating System EPDM

The Acrylic Roof Restoration Coating System EPDM is the Metacrylics system for coating existing EPDM rubber roof membranes. The Metacrylics Installation Spec Book offers it as 10, 15, 20 and 30 year systems on pages 3 to 6, and the system begins with a rinse treatment before any coating.

It is one of the Metacrylics assemblies for EPDM roofs.

The manufacturer's representative EPDM assembly runs from a prepared EPDM surface to Acrylic Clear Base, then polyester fabric, then Extreme Performance Plus Acrylic White.

EPDM Rinse is a low viscosity, sprayable, rinseable primer technology that pretreats a black EPDM rubber membrane before power washing and coating. It is made for use with Metacrylics acrylic or silicone coatings and improves coating adhesion to EPDM. It has a neutral pH and uses APEO-free surfactants.

• Appearance: clear liquid; color pink to purple; odor mild.
• pH 6-7; specific gravity 1.01 g/cc; wet density 8.46 lbs per gallon.
• Completely soluble in water.
• Dilution during pressure washing: one part EPDM Rinse to 300 parts water.

Laboratory wet adhesion on black EPDM, tested to ASTM C794 with a two-coat application of 18 to 20 dry mils, was 0.4 pli on new EPDM and 0.5 pli on aged EPDM after a plain pressure wash, and 1.2 pli on new EPDM and 1.4 pli on aged EPDM after EPDM Rinse followed by a pressure wash. A roof trial reported adhesion pulls after 7 months of exposure on a Building 48 roof.

EPDM Rinse is spread at 500 sq. ft. per gallon by spray bottle or by pouring and brushing, and it stays on the surface for a minimum of 20 minutes and up to 2 hours. The membrane is then cleaned with a commercial power washer between 2000 and 3500 psi, worked slowly and close to the surface to remove mica and inorganic release agents. A power washer is needed for adhesion. A faster final rinse continues until the water runs clear with no soap bubbles, and the membrane dries with no visible dampness before it is coated. In the Spec Book the quantity is 0.2 gallons per square (100 sq. ft.), left for 20 minutes before pressure washing.

The 180 degree peel adhesion test uses 3 inch by 6 inch membrane pieces, coating at 18 to 20 dry mils, 14 days of cure at 75 degrees F and 50 percent relative humidity, and a peel rate of 2 inches per minute. Wet adhesion is tested after 7 days of water immersion. A separate ponding blister test forms treated membrane into a bowl.

Aquatic toxicity data classify the rinse as of low concern to aquatic invertebrates and fish (LC/EC50 above 100 mg/L) and moderate concern to algae.

The 10-year coating over EPDM uses these materials per square (SQ, 100 sq. ft.):

• EPDM Rinse: 0.2 gallons.
• Clear Acrylic Base: 1 gallon.
• Acrylic White: 3 gallons.
• 9 inch Stitchbond Fabric with Clear Acrylic Base for seams, and Acrylic Gel with fabric, as needed.

The roof is cleaned, rinsed and pressure washed. Clear Base goes on the whole roof, including parapet walls, flashings and HVAC ducts, and cures 4 to 12 hours. Penetrations are 3-coursed, bad seams are reinforced with polyester fabric and Clear Base, and so are waterways and ponding areas. Acrylic White follows in two applications of 1.5 gallons per square, 24 to 48 hours apart.

Heavier systems add fabric and base. The 15-year system uses 3 gallons of Clear Base, 3.5 gallons of Acrylic White and one square of Stitchbond Fabric per square, with fabric embedded in 2 gallons of wet Clear Base, a further 1 gallon over it, and 24 hours of cure. White goes on in two coats of 1.75 gallons.

The 20-year system uses 4 gallons of Clear Base and 4 gallons of White, with 2 gallons of Clear Base under and 2 over the fabric and 24 to 48 hours of cure; White goes on as two coats of 2 gallons.

The 30-year system uses 6 gallons of Clear Base, 7 gallons of White and two squares of fabric per square. A 5-course penetration detail replaces the 3-course detail, two fabric layers are embedded in wet Clear Base, cure takes 48 hours, 2 gallons of base encapsulate the exposed fabric, and White goes on in four applications of 1.75 gallons.

Acrylic Gel completes the details with fabric. It is a white, gray or clear mastic with solar reflectance 0.87 and thermal emittance 0.90 (CRRC seller ID 0660), Class A fire resistance under ASTM E-108 and UL 790, and wind uplift of 105 PSF. Extreme Performance Acrylic White has solar reflectance 0.90, thermal emittance 0.88, SRI 114, a weight of 11.3 lbs per gallon and a quick-set additive that gives rain resistance at 40 degrees F and 80 percent relative humidity within 2 hours or less.