[Editor’s note: This information is provided by roof membrane manufacturer Dicor. While there’s plenty of “promotion” for their product included, some of the information and principles may be of assistance to our readers.]
In 2011, some RV manufacturers started using new formulations of TPO (thermoplastic olefin) roofing material that has come into the RV marketplace. To 
stay on top of the situation, Dicor tested some of these new formulations against sealants currently available on the market. We found some TPO roofing membranes are not chemically compatible with on-the-shelf lap sealants. When these sealants are used on some new TPO membranes, bloating and disfiguration of the membranes results. This is mostly a cosmetic problem, and does not reduce the performance of the roofing material or sealant, but it’s something you probably want to avoid.
If your RV was built in 2010 or earlier, you needn’t be concerned. But, if you have purchased a 2011, 2012 or later RV model, and you need to do repair work that involves resealing the roof membrane, you should determine if your roofing is TPO or EPDM.
Important Notes:
•If your roofing is EPDM (Ethylene Propylene Diene Monomer), indicated by a colored top and black bottom, you can confidently use Dicor Lap Sealant.
•If your roofing is a solid color all the way through the membrane, or if it has a fleece backing, it is TPO.
•If your TPO has a fleece backing then regular Dicor Lap Sealant will probably be the right choice.
•But if your TPO does not have fleece backing then Dicor Ultra Sealant System should be used.
