how to remove lap sealant from EPDM roof

[jeeplj8]

I am going to replace the vent in our bathroom. The factory (or more likely dealer) did a great job of sealing the original unit, which is less than 1 year old. The lap sealant is wide and thick on the EPDM roof. Instructions suggest scraping off old sealant. Looking at the material, I am not sure how you scrape lap sealant from the EPDM membrane without causing damage.

Suggestions?

[ryand]

I ran in to the same thing when adding a fan over the bedroom....i started to remove the sealant and was pulling on the roof material so bad that i thought it would tear. I scraped off most all of the material on the flange for the vent i was replacing and picked at the remaining sealant until the new fan sat as good as flush as possible. No leaks so far. I think this dicor material is pretty forgiving stuff.

[TexasBBQ]

I've removed a lot of the Dicor lap sealant using a very well used putty knife. The blade was semi flexible and the edge was not sharp, it was somewhat rounded, including the corners. That's what I mean by very well used. I kept the blade parallel with the EPDM and worked it back and forth with slight pressure inward. It worked very well, in most cases it barely left any sealant.

Don't get in a hurry and it'll come up just fine.

[MC9]

Unlike most glues lap sealant doesn't have to be cleaned off squeaky clean. It sticks to stuff just fine. I've done a couple of vents and it hasn't been a problem.

[avolnek]

I have used a fairly sharp paint scraper or putty knife to do this. As ryand said I did end up tugging on the rubber roofing a bit but pushed down with my opposite hand on the material i was pulling while using the other to cut the sealant.

When i did mine I ran the blade of the scrapper at a 45* angle to the edge i was cutting on.

[Herk7769]

I have used a plastic putty knife or scraper (might need more that one!) and a heat gun on low to soften hardened Dicor

[jeeplj8]

Originally Posted by herk7769

I have used a plastic putty knife or scraper (might need more that one!) and a heat gun on low to soften hardened Dicor

supposed to be low 90's next week, so by the time I get home from work I am hoping it is good and soft!

[jeeplj8]

Thank you for the advice, this went somewhat more easily than I expected. I found the lap sealant was nice and soft as I expected at 98 degrees. (It was much cooler by the time I started, about an hour and a half before sunset, still around 87 though.) I ended up more cutting away from the rubber roof material than scraping it off. I found I could slide a putty knife along and leave just a thin film of old sealant.

I used the butyl tape instead of the foam gasket the instructions called for. I found it interesting the fantastic fan uses far less screws that the original and is a plastic housing as opposed to metal.

I then layed on the lap sealant pretty heavy and finally installed the vent cover. I am surprised that the vent cover is held in place by 4 cotter pins. I would think they might vibrate loose and come off going down the road.

[TexasBBQ]

Looks good and water tight. Hope it works out good.

[BigTJohn]

Good thing to do and the Fantastic vent cover provides almost 100% air flow over any other cover. Looks good.

[sirbob]

Jeep thank you for posting the pics before and after your work. I recently chose 2 of these covers for the airflow for my power fan, over the easier installation of a MAXXAir vent cover. Was courious to see how difficult it might be to safely remove the sealant from the base for the installation.

Great job!

[rvroofer]

Everything looks great instead of lap sealant we use a 4" fiber back seam tape(tape-kote) then seal with our 20 year rv roof coating.