Sikalastic®-646 Lo-VOC

Single component, moisture triggered, aliphatic polyurethane

15 months

Store dry between 35 °F and 77 °F (2–25 °C). Condition material to 50–77 °F (10–25 °C) before using for ease of application.

11.9 lb./gal. (1.4 kg/cm³)

** Best practice is to apply total wet film thickness in (2)two coats.
(i.e. RoofCoat 20 applied in (2)two 20 mil wet coats)

Localized Reinforcement: Sika® Joint Tape SA or use Sika® Flexitape Heavy embedded in 25-35 wet mils of Sikalastic®-646 Lo-VOC, centered over seams, transitions and properly treated cracks and joints.

Note: Coverage rates provided are optimal and are not guaranteed - coverage rates will vary depending on temperature, surface roughness, porosity, aggregate selection, embedment, and application technique.

-22 – 176 °F (-30 – 80 °C) intermittent

Most common roofing contaminants, oils, grease, dilute acids and bases.

41 - 95 °F (5 - 35 °C)

80 % R.H. max.

Beware of condensation. The substrate and uncured coating must be ≥ 5 °F (3 °C) above dew point.

41 - 140°F (5 - 60°C)

≤ 4 % moisture content as measured with a Tramex Moisture Meter. No rising moisture according to ASTM (Polyethylene-sheet).

If moisture content is above 4 %, use Sikalastic-GDC Primer.

In opened containers, the material will form a film after 1–2 hours approx. at 75 °F (24°C) and 50 % R.H.

 *After 7 days the surface must be cleaned and primed with Sika® Reactivation Primer or Sika® Concrete Primer Lo-VOC before continuing.
Note: Times are approximate and will be affected by changing ambient conditions particularly temperature and relative humidity.

Note: Times are approximate and will be affected by changing ambient conditions particularly temperature and relative humidity.

Substrate Pre-Treatment
Refer to Priming Guide to select primer for properly evaluated and prepared substrate. Refer to separate primer Product Data Sheet for application methods, coverage rates, cure times and recoat windows. Always allow primer to cure thoroughly before applying detail or base resin layer.

Sikalastic® RoofPro-646 Lo-VOC Priming Guide

Substrates and Primer Options
Concrete *1
Sikalastic® Concrete Primer Lo-VOC
Sikalastic® DTE Primer
Sikalastic® GDC Primer
Sikalastic® EP Primer/Sealer
Sikalastic® EP Primer Rapid
Lightweight Structural Concrete *1
Sikalastic® Concrete Primer Lo-VOC
Sikalastic® DTE Primer
Sikalastic® GDC Primer
Sikalastic® EP Primer/Sealer
Sikalastic® EP Primer Rapid
Cement, Gypsum Based Roof Boards
Sikalastic® Concrete Primer Lo-VOC
Sikalastic® EP Primer/Sealer
Sikalastic® EP Primer Rapid
Brick, Stone *3
Sikalastic® Concrete Primer Lo-VOC
Sikalastic® EP Primer/Sealer
Sikalastic® EP Primer Rapid
Bituminous Substrate
Asphalt, Bituminous Felts, Bituminous
Coatings, Granulated or Smooth
SBS & Aged APP Cap Sheets *2,3
Sikalastic® EP Primer/Sealer
Sikalastic® EP Primer Rapid
Single Ply PVC Membranes *3
Sarnafil, Sikaplan *3
Sikalastic® EP Primer/Sealer
Hypalon *3
Sika® Bonding Primer
TPO, EPDM *3
Sikalastic® EPDM Primer
Sikalastic® EPDM / TPO Primer Lo-VOC
Roof Tiles (unglazed) *3,4  
Sikalastic® EP Primer/Sealer
Sikalastic® EP Primer Rapid
Fiberglass *3  
Sikalastic® EP Primer/Sealer
Sikalastic® EP Primer Rapid
Polyurethane Foam - Sprayed or Slab Stock
Sikalastic® EP Primer/Sealer
Sikalastic® EP Primer Rapid
Metal *3
Aluminium, Galvanized, Cast Iron,
Copper, Lead, Brass, Stainless Steel,
Steel, Zinc
Sikalastic® EP Primer/Sealer
Sikalastic® EP Primer Rapid
Pre-Coated Metal *3  
Paints & Coatings *3
Aluminized Solar Reflective Coatings *3
Sikalastic® EP Primer/Sealer
Sikalastic® EP Primer Rapid
Wood - Timber & Plywood *5  
Sikalastic® EP Primer/Sealer
Sikalastic® EP Primer Rapid
* Consult Sika.
1 New cementitious substrates must be Portland base and be cured min. 28 days.
2 The presence of volatile bitumen may cause discoloration of Sikalastic® if not properly primed.
3 Surface evaluation and field adhesion testing.
4 Glazed tile consult Sika.
5 Pressure treated lumber consult Sika.

Substrate Evaluation and Preparation

All substrate surfaces shall be clean, dry, and sound. Acceptable substrates include: sound concrete, metals, wood, modified bitumen, mineralized felt, EPDM, Hypalon, TPO, sprayed polyurethane foam, brick and stone, and existing liquid applied membranes.
 

Concrete and Cementitious Substrates
Cementitious or mineral based substrates must be prepared mechanically using abrasive blast cleaning or scarifying equipment to remove cement laitance and to achieve an open textured surface (CSP 2-4 per ICRI guidelines). Loose friable material and weak concrete must be completely removed and surface defects such as voids must be fully exposed.

Repairs to the substrate, filling of joints, voids, and surface leveling must be carried out. Consult Sika for product recommendations based on project requirements. High spots must be removed by grinding or similar method. Outgassing is a naturally occurring phenomenon of concrete that can produce pinholes in liquid-applied materials. The concrete must be carefully assessed for moisture content, air entrapment, and surface finish prior to any roofing work. Particular requirements for priming must also be considered. Installing the primer and membrane either when the concrete temperature is falling or stable can reduce outgassing. It is beneficial, to apply the primer and embedment coat in the late afternoon or evening.
 

Gypsum and Cement-Based Sheathing
Sheathing boards shall be clean, dry, and dust-free, and shall be properly secured to the structure. Loose, damaged, or contaminated boards shall be removed and replaced.

Brick and Stone
Mortar joints must be sound and preferably flush pointed. Power wash and use biodegradable non-sudsing detergent with clean water rinse as required.

Asphalt
Asphalt contains volatiles which can cause bleeding and slight non-detrimental staining. The asphalt must be carefully assessed for moisture and/or air entrapment, grade, and surface finish. Power wash and use biodegradable non-sudsing detergent with clean water rinse as required. All major cracks should be sealed to allow continuity of the Sikalastic® RoofCoat system.

Bituminous Felt
Ensure that bituminous felt is firmly adhered or mechanically fixed to the substrate. Bituminous felt shall not contain badly degraded areas.

Bituminous Coatings
Remove any loose or degraded coatings. Bituminous coatings shall not have sticky or mobile surfaces. Volatile mastic coatings, or old coal tar coatings are not acceptible. Power wash and use biodegradeable non-sudsing detergent with clean water rinse as required. Treat blisters by star cutting and removing any underlying water. Allow to dry and re-adhere using suitable adhesive.

Metals
Metals must be in sound condition. Ferrous metals should be thoroughly cleaned by grinding or blast cleaning prior to priming (SSPC-SP3 to near-white metal). Non-ferrous metals are prepared by removing any deposits of dust and oxidation and abrading to bright metal. Wire brushing can be used for soft metal such as lead. The surface must be clean and free from grease which, if present, must be removed with a solvent wipe or wash with detergent, rinse and dry. Stainless Steel must be mechanically abraded or ground to create an appropriate anchor profile.
 

Paints and Coatings
Remove any loose or degraded coatings. Ensure the surface is clean and free from grease. Ensure the existing material is sound and firmly adhered.

Existing Sikalastic® RoofPro Systems
The existing Sikalastic® RoofPro System shall be soundly adhered to the substrate. Clean the membrane using a pressure washer at approximately 140bar (2000 psi) and biodegradable non-sudsing detergent with a clean water rinse. Allow the membrane surface to dry.   

Wooden Substrates
Timber and timber based roof decks require additional reinforcement such as the installation of plywood, approved insulation, or cover board. Small timber protrusions and suitable decks may be treated directly, provided that the timber is of exterior quality, e.g. plywood. Fill joints flush with Sikaflex® sealant.
 

Sikaplan®/Sarnafil® Membranes
Clean the membrane using a pressure washer at approximately 140bar (2000 psi) and biodegradable non-sudsing detergent with a clean water rinse. Allow the membrane surface to dry.   

Detailing

Non-structural Cracks Up To 1/16''
Detail application not necessary. Apply base coat per below.
 

Non-structural Cracks Between 1/16'' and 1/4''
Rout and seal with Sikaflex®-11 FC sealant.  Allow Sikaflex®-11 FC to skin over. Apply 30-35 mil resin layer embedding 3'' Sika Flexitape Heavy centered over the crack. Alternatively, allow Sikaflex®-11 FC to cure then apply Sika® Joint Tape SA centered over the crack. Apply base coat per instruction.

Metal Seams, Plywood/Cover Board Joints
Apply 30-35 mil resin layer embedding 3 or 6'' Sika® Flexitape Heavy centered over seams. Alternatively, Sika® Joint Tape SA can be applied centered over seams. Apply base coat per instruction.

Transitions Between Dissimilar Materials
Apply appropriate primer for each substrate as indicated in the primer guide.  Apply 30-35 mil of Sikalastic®-646 Lo-VOC embedding 6" Sika® Flexitape Heavy centered over the edge. Apply base coat per instruction.
 

Vertical to Horizontal Transitions
Apply appropriate primer for each substrate as indicated in the primer guide. Apply a 1/2" cant bead of Sikaflex®-11 FC at the transition from horizontal to vertical. Allow Sikaflex®-11 FC to skin over.  Apply 30-35 mil resin layer embedding 6'' Sika® Flexitape Heavy centered over the cant bead. Alternatively, allow Sikaflex®-11 FC to cure then apply Sika® Joint Tape SA centered over the cant bead. Apply base coat per instruction.

Applying Base Coat and Top Coat
Mixing not required. Apply Sikalastic®-646 Lo-VOC at the coverage rate per instuction to achieve the intended/specified RoofCoat System. Resin can be applied with a 1/2'' nap phenolic resin core roller, squeegee or airless spray pump.  Allow base coat to cure through before applying the top coat. Use the overcoat instruction as a guide for approximate cure times for various climate conditions.  Keep base coat clean and dry then apply the top coat resin layer within 7 days. If the window is exceeded clean with non-sudsing detergent and clean water rinse, and allow to dry then apply Sika® Concrete Primer Lo-VOC or Sika® Reactivation Primer. Top coats can be applied by the same means as the base coat. Apply at the coverage rate per instruction to achieve the intended/specified RoofCoat System. Sika recommends using a different color for the base and top coats for quality control.

Seed and Back Roll Option
The Seed and Backroll option is primarily intended for use as maintenance traffic roof walkway applications where enhanced slip resistance is required. Apply Sikalastic®-646 Lo-VOC resin at 15 mils wet film thickness to the installed, cured RoofCoat system. While the supplemental resin application is still wet seed with kiln-dried, iron-free aggregate. Back roll the surface to encapsulate the aggregate in the Sikalastic®-646 Lo-VOC resin.

Full Broadcast and Seal Option
The Full Broadcast and Seal option is intended for use for applications where both enhanced slip resistance and physical protection of the roofing membrane is required. Apply Sikalastic®-646 Lo-VOCresin at 15 mils wet film thickness to the installed, cured RoofCoat system. While the supplemental resin application is still wet broadcast to rejection (full broadcast, beach) with kiln-dried, iron-free aggregate. Remove excess aggregate after cure. Seal with an additional 15 mil coat of Sikalastic®-646 Lo-VOC.

Clean all tools and application equipment with appropriate solvent immediately after use. Hardened and/or cured material can only be removed mechanically.