07 56 00 Fluid-Applied Roofing Recover Sikalastic-500

Sikalastic-500 is a single-component, ultra high solids, liquid-applied silicone roof coating made by Sika Corporation. Its chemical base is moisture-cured silicone. The 07 56 00 Fluid-Applied Roofing Recover system built on it is written for structural concrete, metal, modified bitumen and single-ply roofing membranes. The coating is fully bonded and installed partially reinforced, and it forms a monolithic membrane over the existing roof.

Existing roofs named for the system include modified bitumen and built-up roofs, concrete, EPDM and Hypalon, PVC, TPO and metal. The coating also reinforces penetrations and terminations and makes spot repairs. Sikalastic-500 Accelerator can be mixed in to shorten cure time by up to 50%, depending on application conditions.

• Packaging: 5 gal. (19 L) pail and 55 gal. (208 L) drum.
• Colors: white, tan, light gray, and custom colors on request.
• Shelf life: 12 months, stored closed in a dry, cool place at 40 to 95°F.
• Viscosity: 12,500 ± 2,500 cps at 75°F and 50% R.H.
• Solids: 92 to 96% by mass and by volume (ASTM D2697).
• VOC content: 35.4 g/l; the specification figure is under 50 g/l (ASTM D2369).
• Hardness: 50 ± 5 (ASTM D2240).
• Tensile strength: 300 psi.
• Elongation at break: 250% (ASTM D412).
• Tear strength: 45 lb./in. (ASTM D624).
• Permeability to water vapor: 7.9 US perms (ASTM E96).
• Service range: the coating retains its integrity from -80°F to 250°F (-62 to 121°C).

Solar reflectance is 0.88 (ASTM C1549), thermal emittance is 0.91 (ASTM C1371), and Solar Reflectance Index is 112 (ASTM E1980), for the white coating.

Approvals and standards named for Sikalastic-500 are Miami Dade, NSF/ANSI 61, CRRC and UL 790. The coating is VOC compliant at under 50 g/l, the maximum in California. The membrane is non-flammable. The coating is not intended to be in contact with a constant temperature below -22°F (-30°C) or above 176°F (80°C).

Sikalastic-500 is applied as a single coat over primer, and the coat thickness sets the system length. The RoofCoat names refer to the warranty length in years.

• RoofCoat 10 (10 year): 24 wet mils, 1.5 gal per 100 SF, about 23 dry mils.
• RoofCoat 15 (15 year): 32 wet mils, 2.0 gal per 100 SF, about 31 dry mils.
• RoofCoat 20 (20 year): 40 wet mils, 2.5 gal per 100 SF, about 38 dry mils. Two coats are used for a more uniform application at this thickness.

These coverage rates are minimums, and rough, irregular or granulated surfaces can need more coating to reach the dry film thickness. The guide specification provides for a manufacturer's standard material, or material and labor, warranty. The materials warranty runs at least one year from Substantial Completion.

Every surface is primed and the primer is allowed to cure before details or the base layer go on. The specification pairs substrates with primers as follows.

• Modified bitumen sheets, with an added asphalt bleed blocker: Sikalastic-501 Primer.
• Acrylic elastomeric coatings: Sikalastic-501 Primer.
• Polyurethane elastomeric coatings: Sikalastic-501 Primer or Sikalastic-502 Primer.
• Metal, manually cleaned: the water-based epoxy Sikalastic-501 Primer, which has an added rust inhibitor, or the solvent-based epoxy Sikalastic-502 Primer. Metal surfaces are abraded where appropriate.
• Concrete, masonry and wood wall transitions: Sikalastic-502 Primer.
• PVC, TPO, FP and Hypalon: Sikalastic-503 Primer.
• EPDM: Sikalastic-504 Primer, with Sikalastic-504 Rinseable Primer used to clean the substrate and then washed off before a pull and adhesion test.

An adhesion test (ASTM D903) is done before coating any surface.

Details come first. Sika Flexitape Heavy, a nylon mesh for local reinforcement at structural cracks, expansion joints and transitions between dissimilar materials, is embedded in Sikalastic-500 or Sikalastic-500 Flash. Sika Joint Tape SA, a self-adhering polymeric rubberized tape with a woven polyester facer, is the alternative. Reinforcement strips are at least 3 in. wide, and the coating extends at least 3 in. beyond the edge of a repair, feathered onto the substrate.

Horizontal-to-vertical transitions receive a 3/4 in. by 3/4 in. Sikaflex polyurethane cant. Sikaflex-11 FC, a one-part polyurethane sealant, is used for fillet beads and penetrations, and only under the silicone coating, never on top of it. Exposed sealant over cured Sikalastic-500 is Sikasil WS 295, a one-part silicone sealant. Parapet, wall and curb flashings get a sealant cant bead and reinforced cold joints before the base coat, and terminations at raked-out mortar joints, saw cut joints or under counterflashing are sealed with Sikaflex-11 FC and a top coat of Sikalastic-500.

At drains the opening is blocked, the strainer basket and clamping ring come off, and the liquid coating and reinforcement extend into the throat of the drain. Metal flanges are encapsulated between two or three coating layers.

Drums and pails are mixed with a variable speed drill and jiffy mixer, usually for 3 minutes, to suspend settled pigments. When the accelerator is used it is added at one can per 5 gal. pail and mixed at 300 to 600 rpm without entrapping air. Accelerator is packed under nitrogen, and once opened the whole container is used within a short time. Drying time is 4 hours without accelerator and 2 hours with it, at 75°F and 50% R.H. The recoat window is a maximum of 7 days between coats.

Ambient air temperature is 41°F (5°C) minimum and 95°F (35°C) maximum, with relative humidity at 80% maximum. Substrate temperature is 41°F minimum and 140°F (60°C) maximum. Air, substrate and uncured coating are at least 5°F (3°C) above the dew point. Substrate moisture content is 4% or less by Sika Tramex meter. Application is by brush, roller or airless spray, and the coating is not thinned with solvents. On substrates that outgas, it is applied during falling temperature, because rising temperature can cause pinholing or blistering. Traffic stays off the finished coating for at least 48 hours at 75°F and 50% R.H.

New concrete must be at least 28 days old. Cementitious products such as tile mortar are not applied directly onto the coating. Unvented metal pans, split or sandwich slabs with encapsulated membrane or insulation, cinder fill decks and lightweight insulating concrete overlays are not covered with the system without added deck evaluation. The coating is not used under continuous immersion or where water ponds for more than 48 hours, and ponding areas are resloped. Metal roof projects that carry a warranty are preinspected by a Sika representative for seam detailing. These limits sit alongside the silicone roof coating use that the system is written for.