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Dicor lap sealant or Eternabond tape for new roof vent

rlw999
Explorer
Explorer
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?
19 REPLIES 19

rlw999
Explorer
Explorer
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
Explorer
Explorer
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
Nomad
Nomad
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.
2009 Silverado 3500HD Dually, D/A, CCLB 4x4 (bought new 8/30/09)
2018 Arctic Fox 992 with an Onan 2500i "quiet" model generator

Cummins12V98
Explorer III
Explorer III
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.
2015 RAM LongHorn 3500 Dually CrewCab 4X4 CUMMINS/AISIN RearAir 385HP/865TQ 4:10's
37,800# GCVWR "Towing Beast"

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JIMNLIN
Explorer
Explorer
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 judgment comes from experience, and a lot of that comes from bad judgment" ............ Will Rogers

'03 2500 QC Dodge/Cummins HO 3.73 6 speed manual Jacobs Westach
'97 Park Avanue 28' 5er 11200 two slides

Cummins12V98
Explorer III
Explorer III
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.
2015 RAM LongHorn 3500 Dually CrewCab 4X4 CUMMINS/AISIN RearAir 385HP/865TQ 4:10's
37,800# GCVWR "Towing Beast"

"HeavyWeight" B&W RVK3600

2016 MobileSuites 39TKSB3 highly "Elited" In the stable

2007.5 Mobile Suites 36 SB3 29,000# Combined SOLD

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

mr_andyj
Explorer
Explorer
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
Explorer III
Explorer III
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.
2015 RAM LongHorn 3500 Dually CrewCab 4X4 CUMMINS/AISIN RearAir 385HP/865TQ 4:10's
37,800# GCVWR "Towing Beast"

"HeavyWeight" B&W RVK3600

2016 MobileSuites 39TKSB3 highly "Elited" In the stable

2007.5 Mobile Suites 36 SB3 29,000# Combined SOLD

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

Cummins12V98
Explorer III
Explorer III
Super_Dave wrote:
Both, belt and suspenders, no worries.


YES!!!
2015 RAM LongHorn 3500 Dually CrewCab 4X4 CUMMINS/AISIN RearAir 385HP/865TQ 4:10's
37,800# GCVWR "Towing Beast"

"HeavyWeight" B&W RVK3600

2016 MobileSuites 39TKSB3 highly "Elited" In the stable

2007.5 Mobile Suites 36 SB3 29,000# Combined SOLD

JIMNLIN
Explorer
Explorer
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.
"good judgment comes from experience, and a lot of that comes from bad judgment" ............ Will Rogers

'03 2500 QC Dodge/Cummins HO 3.73 6 speed manual Jacobs Westach
'97 Park Avanue 28' 5er 11200 two slides

Lwiddis
Explorer II
Explorer II
2x on opnspaces opinion.
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opnspaces
Navigator
Navigator
I would put Dicor under the vent and then Eternabond it. Then just don't drive under any low branches.
.
2001 Suburban 4x4. 6.0L, 4.10 3/4 ton **** 2005 Jayco Jay Flight 27BH **** 1986 Coleman Columbia Popup