Lexis Coatings » Roof Coating Technical Support » What are Elastomeric Coatings and Where Can You Use Them?

What are Elastomeric Coatings?

Elastomeric coatings are fluid-applied roofing membranes with elastic properties that allow it to expand and contract with the substrate.
Elongation in roof coatings typically ranges from 300 – 800%. Without good elongation, a roof coating is no longer considered an elastomeric. As the membrane thickness goes up, elongation increases while tensile strength decreases. Elongation is important because roofs tend to expand and contract to allow the coating to move with the substrate and not crack or peel off. ASTM D6083 requires a dry film thickness of 20 dry mils for testing.

Membrane Thickness

Proper film thickness is essential to achieve the desired performance in elastomeric roof coatings. In general, elastomeric roof coatings should be applied at a minimum of 20 dry mils dry film thickness (DFT) to meet the physical properties in the technical data sheet.

Correct film thickness is key to effectively protect the substrate from UV degradation. A thin coat will not have enough UV blocking and crack bridging capability. This is the reason why we tint our primers to a dark color. A dark surface will show through the coating and make a white coating look gray.

Oftentimes, contractors will sell a 2 coat system but fail to specify the total dry film thickness of the installed membrane. If in doubt, please ask us for details and clarification. They should strive to put down at least 30 dry mils to ensure they are getting at least 25 dry mils on any thin areas.

Elastomeric coatings sold in home improvement stores that are intended for masonry, stucco or brick are not designed for roofing applications. Be sure you have the right product!

Types of Elastomeric Coatings

Water Based

Water-based, acrylic elastomeric roof coatings are widely used over metal roofs and spray foam roofs by contractors and building owners performing a DIY restoration. They are best used on roofs that don’t pond water.

Solvent Based

Solvent-based elastomeric coatings have higher ponding water resistance and is more suitable for low slope or flat roofs. Solvent-based roof coatings have much better ponding water resistance than acrylic roof coatings.

How to Apply Elastomeric Roof Coatings

Metal Roof Coating Application with Airless Sprayer

Airless Spreader

Airless spray equipment provide quick application with even coverage over uneven areas and roofs with a lot of penetrations or HVAC units. They are available in several models and can be customizable for each coating which eliminates the need to purchase additional rigs. Acrylic coatings can use a roof rig with a 2,000 psi pressure, 1.5 gpm spray rate and a 631 spray tip. Silicone coatings requires a larger rig with higher pressure and a 4.0 gpm spray rate.

Elastomeric Coating Application by Coating Spreader

Coating Spreader

Roof coating spreaders offer low cost, even coverage and quicker clean up than other application methods. With roller widths up to 40", they can cover 1200SF a minute. Special profile rollers for metal roofs. Spreaders are especially useful on projects where overspray is a concern.

Elastomeric Coating Application by Power Roller

Roller / Power Roller

Foam rollers can be used over flat roofs when applying primers. Long nap rollers are recommended for base coats and finish coats. Roof rigs can also be fitted with a power roller attachment to speed up the process.