When can spray foam be used on your roof?

AAR Expert Will Lorenz spray foam is a great product to put over an existing roof system and on new construction.

Editor's note: The following is a transcript of a conversation with Will Lorenz partner of General Coatings. You can listen to the interview or read the transcript below.

Lauren White: Hello, everyone. My name is Lauren White, here with AskARoofer.com, and I am joined by the one and only Will Lorenz. Will, it's good to see you. 

Will Lorenz: Hello, Lauren. Fabulous to talk with you again about roofing opportunities. 

Lauren White: Yeah, we're so excited that you're one of our AskARoofer experts. And our question this month for the month of April is, when is it acceptable to install a new roof over an existing roof? 

Will Lorenz: Well, Lauren, that's a great question. Thank you very much. We're a manufacturer of spray polyurethane foam roofing systems, and spray foam is a great product to put over an existing roof system. If you have a built-up roof and you need to extend the life of it, you need to insulate it better, waterproof it, spray foam is a great choice. Put an inch or two of spray polyurethane foam over it on roof coatings, and you seal up that roof and get it performing for another 15 or 20 years.

Spray foam is also great as a new construction. So if you had to do a tear off, you found that the existing roof was wet or damaged and you needed to remove it, spray foam's a great choice to put the new deck, whether it's concrete, metal or plywood.

So we have the solutions with spray foam for this opportunity. 

Lauren White: Yeah, amazing. Well, yeah, anything else you think people should know about, you know, what to look for when installing a new roof over an existing one? 

Will Lorenz: Yeah, I think, you know, it's always about moisture and the stability of the deck. If it's damaged and structurally unsound, then you need to remove the system. If it's loose and can't be fastened down, it needs to come off. If it's wet, boy, wet's a problem. It continues to cause things such as mold and rot, as well as, you know, just poor performing insulation. So code requires wet materials to be removed. And that's what I always tell people, getting up on a roof and you see things that are wet, if it's a small portion, you can tear it out and then replace it. If it's more than 25% of the roof, the solution really needs to be to tear it off.

But if it's in good condition and dry, and it's just failing at the seams or at the edges, then a spray foam roof system is a great alternative to get it back functional.

Lauren White: Perfect. Well, well, thank you so much. We appreciate your insights as always, and we can't wait to hear what you have for next month. 

Will Lorenz: Thank you again. Appreciate the opportunity.