Sikalastic-621 Fluid-Applied Roofing

Sikalastic-621 Fluid-Applied Roofing is the Sikalastic RoofPro cold-fluid-applied polyurethane roofing membrane written as CSI section 07 56 00. It is fully bonded and elastomeric, for structural concrete, plywood sheathing, cover board, metal and other substrates. It is installed as a one-ply, fully reinforced, self-flashing membrane. The resin is Sikalastic 621 TC, a single-component, cold, fluid-applied, moisture-triggered, aliphatic polyurethane that conforms to ASTM D7311-07.

The 621 roofing system combines the resin with fiberglass mat or polyester fleece reinforcement to make a membrane and flashing system. It is used in Direct, Plaza, Vegetated and Recover systems and in the 10, 15, 20 and 25 year systems, for new construction and refurbishment. White 621 TC is used for cool roofs and solar roof assemblies. Balconies, terraces, walkways and plazas under foot traffic take a supplemental aggregated surfacing.

Seven builds are written. Each has Sikalastic 621 TC as base and top layers, with the reinforcement between them.

• RoofPro 10 with Sika Reemat Standard, 10 year: base 35 wet mils (about 45 sf per gal), top 30 mils (about 53 sf per gal).
• RoofPro 15 with Sika Reemat, 15 year: base 45 mils (about 35 sf per gal), top 30 mils (about 43 sf per gal).
• RoofPro 15 with Sika Fleece 120, 15 year: base 45 mils, top 30 mils (about 53 sf per gal).
• RoofPro 20 with Sika Reemat, 20 year: base 45 mils, then a 30 mil top layer.
• RoofPro 20 with Sika Fleece 140, 20 year: base 50 mils (about 32 sf per gal), top 35 mils (about 45 sf per gal).
• RoofPro 25 with Sika Reemat, 25 year: base 45 mils and two 30 mil top layers.
• RoofPro 25 with Sika Fleece 170, 25 year: base 60 mils (about 26 sf per gal), top 40 mils (about 40 sf per gal).

The warranty is the manufacturer's standard warranty, with a materials warranty of at least one year from Substantial Completion and system warranties of 10, 15, 20 or 25 years.

• Viscosity: 5 to 20 Pa.s (ASTM D2196).
• Volume solids: 80% minimum (ASTM D2697). Weight solids: 86% minimum (ASTM D1644).
• Sag resistance: no sag at 700 micrometers, 0.028 in. (ASTM D4400).
• Tensile strength: 270 lb/in2 minimum (1.86 MPa). Elongation: 200% minimum (ASTM D412).
• Accelerated weathering, 5000 hours (ASTM G154): no cracking or checking.
• Water vapor transmission: 8.5 g/m2 per day maximum (ASTM E96).

The installed system is a continuous barrier against liquid water and does not permit the passage of water. It withstands design pressures calculated under the most current revision of ASCE 7. The membrane resists gasoline, paraffin, fuel oil, mineral spirits, moderate acid and alkali solutions, acid rain and detergents. Some low molecular weight alcohols can soften it. It can serve as a temporary roofing barrier at 15 to 20 wet mils on a prepared deck, and it does not need to be removed before the finished roofing goes on.

• Packaging: 5 gal. (19 L) pail.
• Colors: white, pearl gray and steel gray, with custom colors at a minimum order quantity.
• Shelf life: 9 months, stored dry at 35 to 77°F (2 to 25°C) and conditioned to 50 to 77°F before use.
• Density: about 12 lb./gal. (about 1.44 kg/l). VOC content: 183 g/l. Solids by volume: 81%.
• Solar reflectance 0.85, thermal emittance 0.87 and Solar Reflectance Index 108, for white.
• External fire performance: Class A (ASTM E108). Approvals and standards: ASTM E108, ASTM D6083 and ASTM C836.
• Service temperature: -22°F to 176°F (-30 to 80°C).
• Chemical resistance includes paraffin, petrol, fuel oil, white spirit, acid rain and detergents.

For a Sikalastic 20 system, static puncture resistance is over 55 lbf with both reinforcements (ASTM D5602). Tensile strength is 1030 psi with Sika Reemat and 900 psi with Sika Fleece 140. Elongation at break is 21% and 82%. Tear strength is 300 lbf/in and 200 lbf/in (ASTM D624). Minimum dry film thickness in the data sheet is as follows.

• Metal roof guide: 32 mils.
• Reemat builds Sikalastic 10, 15, 20 and 25: 51, 59, 61 and 85 mils.
• Fleece builds Sikalastic 15, 20 and 25: 61, 69 and 85 mils.

Coverage options run from 80 sf per gal at 20 wet mils to 35 sf per gal at 45 mils with Reemat, and from 25 sf per gal at 65 mils to 16 sf per gal at 100 mils with Fleece.

Ambient air is 41 to 95°F (5 to 35°C) with relative humidity at 80% maximum. Substrate is 41 to 140°F (5 to 60°C), at least 5°F (3°C) above the dew point, and 4% moisture or less by Tramex meter. In an opened container the material forms a film after about 1 hour at 75°F and 50% R.H. Application is by brush, roller, spray or squeegee, with no mixing.

• At 40°F and 50% R.H.: rain resistant in 10 minutes, touch dry in 12 hours, full cure in 24 hours, overcoat after 14 hours.
• At 50°F: 10 minutes, 6 hours, 18 to 24 hours, overcoat after 6 hours.
• At 70°F: 10 minutes, 4 hours, 12 to 18 hours, overcoat after 5 hours.

After 7 days the surface is cleaned and primed with Sika Reactivation Primer. The membrane can cure while immersed right after application. Rain on uncured membrane can leave pock marks, which do not limit performance.

The priming guide covers concrete, lightweight structural concrete, cement and gypsum roof boards, brick and stone, bituminous substrates, PVC, Hypalon, TPO and EPDM, unglazed roof tiles, fiberglass, polyurethane foam, metals, pre-coated metal, paints and coatings, aluminized solar reflective coatings, and wood. Primers include Sikalastic Concrete Primer Lo-VOC, DTE Primer, GDC Primer, EP Primer/Sealer, EP Primer Rapid, Sika Bonding Primer for Hypalon, and Sikalastic EPDM / TPO Primer Lo-VOC.

Reinforcement at cracks is Sika Flexitape Heavy or Sika Joint Tape SA. Cracks up to 1/16 in. need no detail. Cracks from 1/16 in. to 1/4 in. are routed and sealed with Sikaflex, then covered with a 40 to 45 mil resin layer embedding 3 in. Flexitape Heavy. Joints from 1/4 in. to 1 in. get bond breaker tape and 6 in. Flexitape Heavy, and wider joints are treated as expansion joints.

New concrete is at least 28 days old. The membrane is not applied on grade concrete decks, under continuous immersion or directly under cementitious tile mortar, and it is not recommended over ceramic tile. Unvented metal pans, sandwich slabs, cinder fill and lightweight insulating concrete overlays need added deck evaluation. Areas with heavy foot traffic receive a wear coat with slip resistant aggregate. For roofs where fleece or mat reinforced liquid-applied membranes are used, the 621 builds cover warranty lengths from 10 to 25 years.