Where Should Butyl Tape Go When Installing Rood Membrane?

Updated 10/23/2025 | Published 04/02/2025

Question:

When installing side trim does the butyl tape go on the camper then tpo membrane then another strip of butyl on the trim? The video shows you adding under membrane but didnt notice any butyl added to the trim. I hope this question is clear enough to understand. Thank for your response.

asked by: Rich N

Expert Reply:

Hello Rich, good question. One layer of butyl tape is typically enough to keep things sealed. So if you do one layer under the membrane that should be fine. You can add a second layer on top of the membrane for extra protection if you wish, but it would not be necessary.

expert reply by: Jesse M

Jesse M.

10/22/2025

Hey Rich, how did things go with sealing the side trim using the butyl tape and TPO membrane? Your update could make it easier for the next person working on the same roof setup.

Rich N.

10/22/2025

@JesseM, The TPO roof install went well I put the butyl tape on the trim and not under the roof membrane. The manufacturer had it that way as well. Then I chaulked the the top of the trim with non-self leveling dicor. No leaks after several down poors of rain. Thank's for your help on the subject matter.