Silicone vs Elastomeric Roof Coating for Arizona Foam Roofs

Silicone and acrylic are both elastomeric roof coatings, but they age, collect dirt, and accept future repairs differently. Based on Durafoam Roofing’s experience maintaining foam roofs around Phoenix, owner Curtis Forstie generally favors acrylic because it offers a simpler, more flexible maintenance path.

Silicone Costs More Without Simplifying Installation

For a new foam roof, surface preparation, application time, and disruption to the homeowner are generally similar for silicone and acrylic elastomeric coatings. Primer requirements depend on the foam substrate and the coating manufacturer.

The major difference is initial material cost. In a recent conversation with our supplier, silicone coating cost more than three times as much as acrylic for the raw materials alone. In our opinion, that massive increase does not translate into a superior product.

The cost difference can continue into future maintenance. An acrylic-coated foam roof is usually straightforward to clean, repair, and recoat with another compatible acrylic system. Once silicone is applied, future work generally must stay within a compatible silicone system because acrylic will not bond correctly when applied directly over silicone.

The cost of silicone coating is over 3x the cost, just for the raw materials. This is a massive difference in cost, and in our opinion does not translate into a superior product.

— Durafoam Roofing Team

Ponding Water Is Silicone’s Main Practical Advantage

Silicone generally handles ponding water better than acrylic, so it can have an advantage in stubborn low areas. Acrylic performs very well when a roof drains properly, but we do not like relying on any coating to solve a drainage problem.

If water consistently sits around drains, scuppers, low spots, or air-conditioning units, the better approach is to correct the drainage first. That often means adding foam to build up low areas or improve the slope before applying the protective coating.

Around drains and scuppers, correct preparation and detailing are at least as important as the coating selected. We view the coating strictly as protection for the foam—not as a substitute for correcting drainage or as the roof’s drainage membrane.

We like to look at the coating as strictly a protectant for the foam, not a waterproof or drainage membrane.

— Durafoam Roofing Team

Phoenix Dust and UV Exposure Affect the Coatings Differently

Both systems can handle Phoenix heat and intense UV exposure when installed and maintained properly, but they age differently. Acrylic elastomeric coating tends to remain bright and reflective. It can chalk and gradually lose thickness through weathering and UV exposure, which is why periodic recoating is part of foam-roof maintenance.

Silicone is highly UV resistant and does not chalk in the same way. In our experience, however, it picks up and holds more of the dirt and dust that accumulates on an Arizona roof. The surface can become gray or brownish over time. As it gets darker, it can lose some of the desired reflectivity and absorb more heat.

Monsoon rain may remove loose dirt, but it does not necessarily restore silicone’s original bright-white appearance. That difference in dirt pickup and long-term reflectivity is one reason we usually prefer acrylic elastomeric coating.

Acrylic Offers a Simpler Repair and Recoat Process

When an existing acrylic coating remains sound, maintenance is usually straightforward. We can pressure-wash the roof, complete any needed foam or coating repairs, confirm that the surface is clean, and apply another compatible acrylic coating.

Silicone may require substantially more preparation. Depending on the existing silicone, its manufacturer, and the proposed new system, the work may include thorough power washing, a manufacturer-approved solvent or surface treatment, etching the existing coating, another rinse and cleaning, and possibly a compatible primer.

Silicone is naturally difficult for other materials to adhere to, so the surface must be extremely clean. Compatibility can also be an issue between silicone products from different manufacturers. Once a roof moves to silicone, future repairs and recoats generally must remain within the same compatible silicone system. Acrylic leaves a simpler and more flexible maintenance path over the roof’s life.

Once you go to silicone, future repairs and re-coats generally need to remain within the same compatible silicone system.

— Durafoam Roofing Team

What We Look for on an Existing Arizona Foam Roof

On an existing foam roof, we usually favor acrylic when the roof is in good condition, drains reasonably well, and needs to remain easy to maintain and recoat. Properly maintained acrylic stays highly reflective and is straightforward to clean, repair, and recoat later.

Persistent ponding that cannot realistically be corrected could make silicone worth considering because it handles standing water better. Even then, our preference is typically to correct low areas with additional foam before recoating. An existing silicone system may also affect the available choices, although compatibility requirements can make us cautious about taking on that roof.

The recommendation therefore depends on what is already on the roof, whether it drains, and how practical future maintenance will be—not simply on choosing the coating with the strongest claim in one category.

Why Our Recommendation Changed After Revisiting Arizona Roofs

Many years ago, we applied silicone to numerous Arizona foam roofs, particularly where ponding water was a concern. After watching those roofs age, revisiting them for maintenance, and seeing how much acrylic elastomeric coatings have improved, we changed our approach over the last 10 to 15 years.

Today, we almost always recommend a quality acrylic elastomeric coating for foam roofs. It provides better long-term flexibility, remains reflective when properly maintained, is easier to clean and recoat, and does not lock the homeowner into a silicone-only maintenance path.

Although no coating should be selected without inspecting the roof, at this point we do not see a condition where we would choose silicone over a quality acrylic elastomeric coating on a foam or flat roof. When ponding is the concern, we would rather repair the low area with foam and then protect the corrected roof with acrylic.

It doesn't lock the homeowner into a silicone-only maintenance path.

— Durafoam Roofing Team