New Skylight: Dicor, or Eternabond, or both?

[RVhiker]

I'm putting a new skylight on my trailer. I have used Eternabond over all caulking on the roof. The new skylight will be installed using butyl caulk between the lip of the skylight and the roof membrane.

Should I:

1) use Eternabond only over the screws and lip of the skylight
2) or should I first use Dicor, let the Dicor cure, and apply Eternabond over the Dicor?

[mayo30]

daamac wrote:
There seems to be a range of opinions. Thanks for all comments.

wgriswold wrote:
If your new skylight is polycarbonate (Lexan?) do not use Dicor. There is a different caulk that is recommended, but I can't remember the name.

I did some searches regarding polycarbonate skylight sealants and found mention of Surebond SB140 Skylight sealant... here's a link:SB-140. SB-140 specs state it is compatable with rubber - like my EPDM roof. So this is the correct sealant.... Right?

This product works super.

[hypoxia]

wgriswold wrote:
If your new skylight is polycarbonate (Lexan?) do not use Dicor. There is a different caulk that is recommended, but I can't remember the name.

This is the list I got from my polycarbonate skylight manufacturer (Majestic Formed Plastics), also RTV 5818.

Recommended Sealants, Gaskets, & Tape

Type Mfg Prod Name

Silicone General Elec Waterford NY 800-255-8886 Ultrapruf Sealant

Silicone General Elec Waterford NY 800-255-8886 Silpruf Sealant

Silicone General Elec Waterford NY 800-255-8886 Construction 1200 Sealant

Silicone General Elec Waterford NY 800-255-8886 Construction 1000 Sealant

Gasket/Tape Norton Co Granville NY 800-724-0883 Norrene® Foam V-2100 UrethaneSeries

Gasket Tremco Columbus OH 800-321-6357 Silicone (70 Durometer) EPDM (60, 70Durometer)

Tape Tremco Cleveland OH 800-321-7906 440 Tape

Butyl Tape PTI Dayton OH 800-543-7570 303,606

Butyl Tape Schnee-Morehead Irving TX 241-438-9111 Isocryl 5600 Series

Aluminum
Mesh Tape DRG Sellotape Utrecht Holland 030 44 33 44 Sellotape BV Vent Tape

Vent Tape 3M Minneapolis MN 612-733-1110 Tape 394


COMPATIBLE CLEANERS FOR SKYLIGHTS: The following cleaning agents have been found compatible with polycarbonate skylights. The manufacturer’s recommendations & instructions should be followed. FORMULA 409 (Reg. trademark of Clorox Company), JOY and TOP JOB (Reg. trademarks of Proctor & Gamble), PALMOLIVE LIQUID (Reg. trademark of Colgate Polmolive), WINDEX with AMMONIA D (Reg. trademark of Drackett Products Co.), VM&P grade naptha, Freon TF.


CAUTION: System compatibility is essential to ensure long-term performance of polycarbonate skylights. Do not expose polycarbonate skylights to solvents such as acetone, toluene or methylene chloride. Before choosing a sealant for your skylight installation, check the sealant’s compatibility with polycarbonate.


Sealant manufacturers will be able to assist you with compatibility inquiries.

[spadoctor]

Not a fan of Eternabond....had many issues with it sticking and where it did stick was a bear to get off. Ill stick with caulking....I use the same as the manufacturer used during the build.

[wgriswold]

daamac wrote:
There seems to be a range of opinions. Thanks for all comments.

wgriswold wrote:
If your new skylight is polycarbonate (Lexan?) do not use Dicor. There is a different caulk that is recommended, but I can't remember the name.

I did some searches regarding polycarbonate skylight sealants and found mention of Surebond SB140 Skylight sealant... here's a link:SB-140. SB-140 specs state it is compatable with rubber - like my EPDM roof. So this is the correct sealant.... Right?

Yes, that is the one. The company I bought my new skylight from included a tube with the skylight. I used butyl tape to seal the skylight to the roof and then caulked with the SB-140.

[RVhiker]

There seems to be a range of opinions. Thanks for all comments.

wgriswold wrote:
If your new skylight is polycarbonate (Lexan?) do not use Dicor. There is a different caulk that is recommended, but I can't remember the name.

I did some searches regarding polycarbonate skylight sealants and found mention of Surebond SB140 Skylight sealant... here's a link:SB-140. SB-140 specs state it is compatable with rubber - like my EPDM roof. So this is the correct sealant.... Right?

[wgriswold]

If your new skylight is polycarbonate (Lexan?) do not use Dicor. There is a different caulk that is recommended, but I can't remember the name.

[JIMNLIN]

daamac wrote:
I'm putting a new skylight on my trailer. I have used Eternabond over all caulking on the roof. The new skylight will be installed using butyl caulk between the lip of the skylight and the roof membrane.

Should I:

1) use Eternabond only over the screws and lip of the skylight
2) or should I first use Dicor, let the Dicor cure, and apply Eternabond over the Dicor?

1. definately use the butyl as the first line of defense against leaks.

2. having helped my neighbor (days) remove yards of newby installed Eternabond from his new to him RV trailer I sure wouldn't use it over screw heads if you ever plan on being the next person that may have to remove those screws. I would do it like OEM and simply seal it self leveling Dicor or equivalent product as the second line of defense behind the butyl.

If you decide to use the Eternabond then seal the edges with Dicor as the pro's do. Makes it look OEM instead of like long band aids lay around the roof with exposed edges. Lots of how to you tubes on this subject.

[westend]

What about Eternabond Double-Stick for a one product solution. Give them a call and see if it is listed for that application is what I would suggest.

I used Eternabond webseal under some fixtures and the screws were sealed exactly like in this video.

[Weldon]

I put dicor down then covered with eternabond.

[time2roll]

Skip the butyl and eternabond. Just use Dicor.

[Ed_Gee]

I believe Eternabond is supposed to be applied to a CLEAN RV surface, NOT on top of Dicor! Many new coaches I've looked at only have Eternabond on the roof main joint seals. Mine has some Dicor applied to the top of the Eternabond. When properly applied, Eternabond is pretty good stuff.

[2oldman]

Maybe you'll be luckier than I with sealing a skylight. No, I didn't install it, but I had a small leak that I could never patch, even with EB and caulk.

Finally ended up painting the frame with several coats of Heng's roof seal. Leak gone.