Sikalastic-641 Lo VOC Fluid-Applied Roofing & Recover

Sikalastic-641 Lo-VOC Fluid-Applied Roofing and Recover is Sika Corporation's CSI section 07 56 00 for the Sikalastic RoofPro system. It is a cold-fluid-applied polyurethane roofing and waterproofing membrane for structural concrete, plywood sheathing, cover board, metal and other substrates, including recover work over existing membranes. The membrane is fully bonded and elastomeric. Work covered includes substrate preparation and the sealing of air leakage and water intrusion pathways at roof-to-wall connections and penetrations such as piping, conduit and ducts.

The resin is a single-component, moisture-triggered, aliphatic, low-odor, low-VOC polyurethane. It saturates and embeds the reinforcement of the roofing system and serves as the top coat. It is typically applied in Sikalastic Direct, Plaza, Vegetated and Recover systems, and in the 10, 15, 20 and 25 year systems, including Built Up and Plaza Deck systems, in new construction and refurbishment.

The coating is a brush or roller-applied, one-component, elastomeric polyurethane with these minimum properties.

• VOC content: under 50 g/l (ASTM D2369).
• Volume solids: 89% minimum (ASTM D2697). Weight solids: 92% minimum (ASTM D1644).
• Sag resistance: no sag at 700 micrometers, 0.028 in. (ASTM D4400).
• Tensile strength: minimum 270 lb/in2 (1.86 MPa) (ASTM D412). Elongation: minimum 200%.
• Five thousand hours of accelerated weathering (ASTM G154) produce no cracking or checking.
• Water vapor transmission: maximum 8.5 g/m2 per day (0.033 perm-inches) (ASTM E96).
• Mandrel bend: pass (ASTM D522).
• Tear resistance: minimum 5.8 kN/m (33 lbf/in).
• Indentation hardness: 82 durometer units, plus or minus 5 (ASTM D2240).
• Dynamic puncture resistance: minimum 15 joules (ASTM D5635). Static puncture resistance: minimum 45.5 lbs (ASTM D5602).

The installed system withstands design pressures calculated under the most current revision of ASCE 7, and the manufacturer carries a cradle-to-grave life cycle analysis and an Environmental Product Declaration under ISO 14025:2006.

Approvals and standards named for Sikalastic-641 Lo-VOC are FM Approval Standard 4470 for Class 1 roof covers, UL 790 Class A, Miami-Dade, ASTM D6083, ASTM E108, ASTM C836, CRRC, Florida Building Code and ICC-ESR-4509.

Where a project requires them, the specification provides for FM Global certification that the membrane meets Approval Standard 4470 for Class I roof covers on non-combustible substrates, with a Class 1 documented wind uplift rating, a hail rating of SH and an ASTM E108-00 Class A approval at a slope of 1 in 12. It also provides for a roof system tested under Miami-Dade TAS 114-95 Appendix D and FM 4474 Appendix B that reaches a minimum wind uplift of 210 psf.

Seven builds are written into the section, matched to warranty lengths of 10, 15, 20 and 25 years. Each uses Sikalastic 641 Lo-VOC for the base layer and top layer, with the reinforcement embedded between.

• RoofPro 10 with Sika Reemat Standard: base layer 30 wet mils (about 53 sf per gal) and top layer 30 wet mils (about 53 sf per gal).
• RoofPro 15 with Sika Reemat: base 50 mils (about 32 sf per gal), top 20 mils (about 80 sf per gal).
• RoofPro 15 with Sika Fleece 120: base 45 mils (about 35 sf per gal), top 25 mils (about 64 sf per gal).
• RoofPro 20 with Sika Reemat: base 50 mils, top 30 mils (about 53 sf per gal).
• RoofPro 20 with Sika Fleece 140: base 50 mils, top 30 mils.
• RoofPro 25 with Sika Reemat: base 50 mils, then two top layers of 23 mils each (about 69 sf per gal).
• RoofPro 25 with Sika Fleece 170: base 66 mils (about 24 sf per gal), top 34 mils (about 47 sf per gal).

Reemat is the fiberglass mat in these builds, made of random strands. Sika Fleece is a non-woven, needle-punched polyester fleece. The warranty is the manufacturer's standard warranty, with a materials warranty of at least one year from Substantial Completion.

The membrane can serve as a temporary roofing and waterproofing barrier when applied at 15 to 20 mils wet film thickness to a properly prepared deck. A membrane used this way does not need to be removed before the finished roofing system goes on.

Application can proceed when precipitation is imminent. The system can cure while immersed right after application. Rainfall on uncured membrane can leave pock marks, which do not limit performance. The membrane is non-flammable and VOC compliant. It is not intended to sit in contact with a constant temperature below -22°F (-30°C) or above 176°F (80°C), and it resists gasoline, paraffin, fuel oil, mineral spirits, moderate acid and alkali solutions, acid rain and detergents. Some low molecular weight alcohols can soften it.

• Packaging: 5 gal. pail, and a 50 gal drum in white and standard gray base only, made to order.
• Colors: white, standard gray, pearl gray, steel gray, mushroom and copper green, with custom colors available.
• Shelf life: 15 months for the pail and 6 months for the drum.
• Storage: dry, at 35 to 77°F (2 to 25°C), with material conditioned to 50 to 77°F (10 to 25°C) before use.
• Density: 11.9 lb./gal. VOC content: 38 g/l. Solids by volume: 89%.

The data sheet uses include saturating resin for Sikalastic systems reinforced with Sika Fleece, and embedment and top coat resin for systems reinforced with Sika Reemat. White Sikalastic-641 Lo-VOC is used in cool roofs and solar roof assemblies. Balconies, terraces, walkways and plazas under foot traffic carry a supplemental aggregated surfacing. There are no limitations on vertical application.

Local reinforcement at structural cracks, expansion joints and transitions between dissimilar materials is Sika Flexitape Heavy, a nylon mesh, or Sika Joint Tape SA, a self-adhering polymeric rubberized tape with a woven polyester facer. Fillet beads and penetrations use Sikaflex 11FC, a one-part polyurethane sealant. Exposed terminations are finished with Sikaflex Hyflex 150 LM, a one-part low-modulus hybrid sealant, or Sikasil WS-295.

Primer follows the substrate. Concrete and gypsum-based boards take Sika Concrete Primer Lo-VOC or Sikalastic Primer EP and EP Rapid. Green and damp concrete takes Sikalastic GDC Primer. Metal, modified SBS and approved asphaltic surfaces take Sikalastic EP Primer/Sealer. EPDM and TPO take Sikalastic EPDM or the EPDM/TPO Lo-VOC primer. PVC takes EP Primer/Sealer. Sika Reactivation Primer or Concrete Primer Lo-VOC primes an existing Sikalastic-600 series membrane older than 7 days. SikaFast 3341, a two-component methyl methacrylate adhesive, bonds the system to PVDF (Kynar) finished edge metal. The section is a fleece or mat reinforced liquid-applied roofing system written to cover roof recover as well as new decks.