Did you know that not all elastomeric roof coatings are the same? Many people assume that all white roof coatings are the same product, but this is not the case.  There are several types of coatings that fall under the characterization of “elastomeric,” but in this article, we will examine the differences between the two most common types of elastomeric coatings: Silicone and Acrylic. 

Top 3 Misconceptions 

1.    “Elastomeric coatings are just like paint.”  

a.    Many people believe that if you “paint” your roof with these products they will be effective against the elements, but this is false.  These products are “coatings,” which require application at specific conditions and millage rates to be effective.  The most common reason for coating failures is an application error.  Much of the stigma against roof coatings stem from bad experiences related to poor application standards. The product might have looked good upon completion, but important details were missed or skipped during the application and planning process.  Failure to follow the proper procedure will cause the coating to fail as a roof system when exposed to the elements.

2.    “These products are both used for the same purpose. Acrylics are just cheaper.”

a.    Both products are effective when used for their intended purpose.  Unfortunately, acrylic coatings are often applied on roofs that are incompatible with the product qualities.  Most commercial roofs are too flat, or they have too much ponding water for acrylic coatings to be effective.  So, why are acrylic coatings not effective on a flat roof when silicone coatings are? The chemistry of each product explains this answer.  Each product has a solvent that will re-liquify the product after it has cured into a solid state.  Silicone coating’s solvent is virgin mineral spirits, while acrylic coating’s solvent is water!  So, if the water stays in contact with acrylic coatings for a prolonged period, it will eventually emulsify the coating back into a liquid state. Therefore, you must have good, positive drainage on a roof before considering an acrylic coating as an option.

3.    “Silicone coatings and acrylic coatings last about the same amount of time.”

a.    Silicone coatings are the only UV stable coating on the roofing market.  This stability means that the sun’s UV rays do not break down the material over time as it does with acrylic coatings.  For example, if you placed a ball of silicone roof coating in the desert next to a ball of acrylic roof coating the silicone coating would be the same size and shape 100 years later.  The ball of acrylic would disintegrate into nothing over time!

4.    “These products can be applied over any roof.”

a.    This is another massive misconception of the two products. An in-depth roof evaluation must be performed before deciding whether it is suitable for a roof coating.

The Technical Specs

Let’s start by first looking at the general technical differences between the two products.  

Silicone coatings have greater elasticity (200%-500%) than acrylic coatings (40%-70%).  What does this mean for your roof, you might ask? Silicone coatings can withstand much higher building movement than acrylic coatings.  This is especially true on metal roofs, which move about 1/8” per 20’. 

 Acrylic coatings have better tear resistance.  Once silicone coatings begin to tear, they will tear faster than acrylic coatings will.  Although, it is harder for tears to occur in silicone because of their elasticity.  

Silicone coatings have much higher thermal emittance qualities. Only about 1% of the sun’s energy will penetrate through a silicone coating into the building.  

Which one is better?

This answer isn’t black and white because a multitude of factors plays a part when choosing the best product for you.  In general, acrylic coatings are less costly but have a limited range of roofs that they will be effective when applied over.  Silicone coatings have a more extensive range of roofs that they can be used over and will last longer than acrylic coatings.  Though, silicone coatings have a higher initial cost.  The best way to find out what your most effective option will be is to have Parsons Roofing Company provide you a free roof evaluation!