Liquid Rubber EPDM Application
EPDM Liquid Rubber can be applied directly on many types of substrates that have solid, stable, non-porous and uniform surfaces such as flat roofs. For most substrates, primers are not necessary. As an example, some types of substrates that can be coated with EPDM Liquid Rubber are:
- EPDM Rubber Sheet Roofs
- Galvanized Steel Panel Roofs
- Non-Polished Aluminum Sheet Roofs
- Steel Plates (Painted, Unfinished, Light Rust)
- Fiberglass Roofs
- Wood & Plywood (treated with oil based sealer)
- Non-porous / troweled concrete surfaces / masonry
EPDM Liquid Rubber Planning
The curing process requires an ambient temperature above 12° C. A full cure will be achieved in 4 to 10 days after application, in consistent 21° C. ambient temperatures. Higher temperatures will accelerate cure times and lower temperatures will extend cure times. Although EPDM Liquid Rubber will immediately waterproof, avoid heavy rain until dry to the touch (16 – 20 hours after application). Pitting may occur otherwise.
Pre-Application Inspection of Roofs / Surfaces to be coated
Inspect your roof surfaces for structural damage, tears, leaks, gaps, corrosion, etc. Light surface rust if adhering well to the roof surface can be either lightly sanded or left in place. Heavy rust should be removed and a good corrosion inhibitor / primer should be applied – check with the manufacturer and wait for the recommended dry time before applying EPDM Liquid Rubber over these areas. Any holes, gaps, tears or lifting or separating seams, should be repaired or reinforced prior to application of EPDM Liquid Rubber.
How to prepare roofs for Liquid EPDM
After inspection and repairing any existing damage, all asphalts or silicone type of caulking on the roof / surface, should be removed. Asphalt products are not compatible with EPDM Liquid Rubber. In instances where it is difficult to completely remove asphalts, consider covering with a substantial barrier, such as plywood, metal plates, etc., and then apply EPDM Liquid Rubber over this barrier.
Proflex Flexible Epoxy can be used as a primer on bituminous surfaces such as felt and asphalt. There are slighlty differnt versions, depending on the substrate, inlcuding one to go on poor asphalt, that is filled with ground rubber.
Glossy and slippery finishes such as polished steel and metal surfaces should be abraded to provide a “rougher” finish to the surface to promote adhesion. Some surfaces like polished stainless steel, silicone rubber, PVC and other plastics may have poor adhesion to EPDM Liquid Rubber, and should be avoided. When in doubt, try a test sample first, and / or consult Alltimes Coatings Technical Services Department.
Prior to coating, thoroughly clean and wash the surface with detergent and water, ensuring the surface is free of oils, dirt, debris and flaking paints, etc. If the surface has fungus, mold, mildew, or algae, you may need to soak these areas in a 1/3rd bleach and water solution to kill them. Let soak until the solution evaporates. You will need to scrub (with a stiff brush) the affected areas with soap and water after soaking with the bleach solution, as some biologicals may anchor onto the surface, and must be mechanically removed even after killing. After cleaning, allow the roof to dry thoroughly prior to applying EPDM Liquid Rubber.
Applying liquid EPDM on different surfaces
When applying over wood / plywood, use an oil base primer first. Our EPDM Liquid Rubber can be directly applied over EPDM Rubber Sheets with little preparation other than cleaning as above.
With masonry / concrete, the surface to be coated must be relatively smooth (steel troweled) and uniform (not honey-combed, full of imbedded stones or aggregate breaking the surface, etc.). The surface must be structurally stable, dry, non-porous, and free of oils, debris, and flaking or loose paint. New (green) concrete may need to be aged 30 days or longer to dry moisture content adequately – check with the concrete supplier for aging recommendations. Fill any cracks, or spalling or other surface defects on the concrete surface with Proflex Flexible Epoxy to level and smooth out the surface.
The “porosity” of concrete / masonry can be somewhat subjective and needs to be addressed prior to applying EPDM Liquid Rubber on such surfaces. When in doubt and when time permits, prepare the surface as above and apply a 0.5 mm dft coat of EPDM Liquid Rubber to a test section. Check when cured in about 4 to 10 days, for surface “bubbling” and adhesion. Bad adhesion and “bubbling” indicates that the structure is too porous. In such a case, or when testing times do not permit, it is recommended you apply a coat of Proflex Flexible Epoxy on the concrete first, to “fill in the pores”, let dry, and then apply the EPDM Liquid Rubber over the Epoxy, as per these instructions.
Applying EPDM Liquid Rubber
The Supplies you will need are:
1- An electric drill (not cordless)
2- A paddle mixer for a can or pail.
3- A rubber squeegee attached to a mop or broom handle.
4- A short nap roller attached to a mop or broom handle.
5- A paint brush
6- A rubber spatula
7- Xylene for clean up
Using mop or broom length handles for the squeegee and the roller will allow you to apply the product standing up and not on your knees. Use the paint brush for hard to reach areas. Broadcast & spread using the squeegee. Use the short nap roller to smooth out trapped air and even out the EPDM Liquid Rubber. Unwanted splatters and drips can be cleaned off with rags and xylene or mineral spirits when wet (within 4 hours of application).
It is important to apply an even coat of EPDM Liquid Rubber at the correct thickness. Not enough material will produce a membrane that is to thin with inadequate adhesion and poor film strength. Too much material will be wasteful, will cause long or no cure conditions and may cause excessive swelling with some types of sheet rubber roofs.
The optimum thickness for most purposes is one coat of 20 mils dft. To achieve a 0.5 mm dft. thickness, you should do a spreading rate calculation. For fairly smooth surfaces such as EPDM sheets, un-polished metals, fiberglass roofs, etc., use a spreading rate of about 3.9 sq.m. per US gallon. Reduce this for rougher surfaces such as steel troweled concrete, use a spreading rate of about 2.8 sq.m. per US gallon. When calculating applied surface area, ensure you measure true surface areas. Example; if a roof is corrugated; take into account the corrugations in calculating the surface area.
If you have not applied EPDM Liquid Rubber before, we recommend you apply this in several pre-measured sections. For the first section, apply 1 US gallon, over a 3.9 sq.m. section. By applying 1 gallon over this 3.9 sq.m. area, you will form a 0.5 mm dft. thickness when cured. The key is to spread the product evenly. In 24° C to 29° C, the product will start to thicken up in about 4 hours, so you should plan your work with that in mind. This first US gallon should not take you more than an hour, but it will give you an idea of how fast you can work. On subsequent sections, you may choose to use more material if you feel comfortable applying the product.
1-When ready to apply the first gallon, follow the mixing directions on the can. Using an electric drill with a mixing shaft, run the shaft in the US gallon of EPDM Liquid Rubber until a vortex forms. Pour the pre-measured catalyst into the vortex and let the drill run for about 15 to 20 minutes to thoroughly mix the EPDM Liquid Rubber with the catalyst. Be sure to scrape the sides of the can with a rubber spatula in order to incorporate all of the material. The catalyst is in a plastic bottle and is bluish-purple in color.
2-Pour the catalyzed EPDM Liquid Rubber onto the pre-measured 3.9 sq.m. area in a serpentine line. Use the rubber squeegee to quickly spread the product over the 3.9 sq.m. as evenly as you can. Again, it is stressed that an even application is important.
3-Use the short nap roller to promote a more even distribution of product and to get trapped air bubbles out. After spreading with a squeegee, go over this area with the roller in slow long even strokes. Do several strokes with the roller to get an even and bubble-free application. Use a paintbrush for nooks and crannies and areas where using a roller may be difficult.
You may initially see some roller / brush strokes. EPDM Liquid Rubber®, however, is self-leveling and these roller / brush strokes will level disappear if enough material has been applied.
By applying an even thickness of 1 US gallon of EPDM Liquid Rubber® on a 3.9 sq.m. pre-measured area, you are ensuring the correct dry film thickness is achieved. When applying the next section, overlap an inch or two and blend in the overlap so you have a continuous and seamless membrane when cured.
In 21° C., the applied EPDM Liquid Rubber® will be dry to the touch in about 16 to 20 hours. This will still not be fully cured, but you should be able to walk on the roof / surface. In these temperatures, your newly applied EPDM Liquid Rubber® Roof will be fully cured in about 4 to 10 days. Higher temperatures will accelerate the curing time and, lower temperatures will prolong the curing process.
On some materials, such as EPDM rubber sheets, some swelling may occur due to solvent absorptions after applying EPDM Liquid Rubber®. This is normal. This swelling will recover with time and heat. In 27° C or so, allow 7 to 14 days to recover. In colder temperatures, recovering will take several weeks, as much as 6 to 8 weeks in 16° C.
Applying EPDM Liquid Rubber® too thick in a single application will cause excessive swelling and longer recoveries, thick single coat applications should be avoided. Overly thick applications will take too long to cure, and may not cure in the center.
You will also be able to coat over cured existing EPDM Liquid Rubber® years after the first application. Clean and dry the surface as described above under Surface Preparation. No primers are necessary when recoating over EPDM Liquid Rubber®.
Thinking of spraying Liquid EPDM?
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