Dicor lap sealant or Eternabond tape for new roof vent

[rlw999]

I'm replacing a roof vent with one with a fan. I have both Dicor self leveling lap sealant and some 4" Eternabond tape. The roof is TPO.

The current vent is sealed with lap sealant, but I'm not sure which to use for the replacement.

The way I see it, Eternabond (assuming the surface is clean and prepped) gives a better seal and will last for a decade. But with the drawback that it's very hard to remove if I need to replace the vent again down the road (though cutting it and just leaving it there is an option).

So what do you think, which would you use?

[rlw999]

I should have looked at the fan before I asked this question, I assumed it would have a nice wide flange like the fan it replaced, but it has a plastic flange (narrower at the front) with a couple of projections on each side of the flange that extend to the edge of the flange. So instead of a nice uninterrupted segment of Eternabond tape, I'd end up with notches in it that I'd have to cover well with Dicor anyway.

So, I just used the Dicor and didn't bother with the tape.

Thanks everyone for your advice!

[mwachel]

Dicor for the ease of removal if necessary. You should be getting on the roof a couple times a year minimum for inspection anyway. Re-sealing with Dicor should be easy if needed.

[deltabravo]

Butyl tape under the flange, Dicor on top.

Dicor under the flange is a disaster when it comes time to replace the roof vent.

This is how I do it.

[Cummins12V98]

JIMNLIN wrote:
Be careful about building up height (over old sealant) of lap sealant around roof fixtures/jacks/etc. This can cause water to pool (lake effect) and a future source of water intrusion. BTDT ...I was a member of "more is better" crowd and it was a expensive lesson.

Good point!

I have always removed all the old Dicor possible and then apply new.

[JIMNLIN]

Be careful about building up height (over old sealant) of lap sealant around roof fixtures/jacks/etc. This can cause water to pool (lake effect) and a future source of water intrusion. BTDT ...I was a member of "more is better" crowd and it was a expensive lesson.

[Cummins12V98]

LittleBill wrote:
can dicor be placed over old dicor, or does it all have to be removed to work?

Clean it good with Acetone then apply right over.

[LittleBill]

can dicor be placed over old dicor, or does it all have to be removed to work?

[mr_andyj]

Lap sealant! hands down, Lap sealant!!!
I have used both, and both are excellent, and the tape is incredible in its holding ability.
I have used both for enough years that I have had to remove both many times. The tape is a nightmare to remove, requires a heat gun, and always leaves a residue or "stain" of stuff that is hard to get off. Sometimes it comes off clean for a few inches, then other times it sticks as a mess.
Lap sealant comes off with a scraper or putty knife. Leveling lap sealant flows into all the nooks and is much better sealing odd shapes where the tape will never seal. Tape only seals flat surfaces, where two surfaces meet (like the vent flashing) you will need a bit of lap sealant to keep tape from leaking.
Tape should only be considered when you need that extra strong bond. IF you can make lap sealant work then use lap sealant.

[Cummins12V98]

mobeewan wrote:
I'd put butyl tape under the flange to protect the membrane from the flange then use Eternabond.

Personally I would wet set into Dicor as it gives another layer of protection from water entering.

[mobeewan]

I'd put butyl tape under the flange to protect the membrane from the flange then use Eternabond.

[Cummins12V98]

Super_Dave wrote:
Both, belt and suspenders, no worries.

YES!!!

[JIMNLIN]

My 24 years old 32' 5er has had nothing but Dicor added when the OEM sealant needed help or replacing. The trailer was 4 year old when a crack formed in the skylite over the bed. I replaced it with a vent. I used the grey butyl tape like OEM first. Removed the squeeze out butyl then added Dicor over the scr heads and joint. Haven't touched it since.

I helped a neighbor replace Eternabond on his roof (around two skylites) that some newb had poorly applied. I would never add Eternabond over screw heads. Its a bitzh to remove even when poorly applied.

Having worked on RV and mobilehome mostly roof mfg/repair previously I would never add Eternabond over screw heads. Great stuff for hole repair or repairing long tears in roofing material.

[Lwiddis]

2x on opnspaces opinion.

[opnspaces]

I would put Dicor under the vent and then Eternabond it. Then just don't drive under any low branches.