Sealant

[rwmurphy15]

I am replacing my cracked skylight and I am wondering that the butyl rubber sealant that the manufacturer recommends putting under the skylight will damage my TPO rubber roof.

[JRTJH]

Nope, butyl putty tape is used on every trailer to seal all the J-channel (drip rail) molding, the front cap and the rear cap, the roof vents, tank vents, refrigerator top vent and the TV/radio antenna base. There's no problem using it on the skylight. It's already all over your TPO (or EPDM) roofing membrane.

[chuckster57]

Butyl tape and putty tape are both sealants but they are different. Easiest way to tell the difference:

Butyl tape will stretch when pulled
Putty tape breaks off when pulled.

I have found that putty tape will “squish” down easier than butyl tape when screwing something on the roof. I would use putty in this application.

[rwmurphy15]

The butyl sealant the manufacturer wants me to use comes in a caulking tube. You lay a bead of caulking down on the roof then lay the new skylight on top of the caulking and squish out the caulking. Icon makes the skylight and the butyl caulking. This is not the tape type butyl. Just wanted to make sure the butyl caulk sealant was not a solvent based material since I'm putting it on a TPO rubber roof

[JRTJH]

You might want to contact Icon, the manufacturer and ask specifically if the sealant is compatible with TPO and EPDM roofing. Many sealants have petroleum as a dispersant/thinner and will damage the roofing membrane. If they won't tell your or if they don't know, I wouldn't use it. Butyl putty tape works well, lasts a long time and doesn't damage the roof. Clay putty tape will dry out in 2 or 3 years, but also won't damage the roof.

I'd be reluctant to use anything that the manufacturer can't guarantee is safe on the roof. Remember that there are at least 4 types of RV roofs, so the instructions you're reading may well be intended for an aluminum, a steel or a fiberglass installation.... This is one time caution before proceeding is advisable.

[BigTexRex]

What you need is Dicor sealant--it's compatible with TPO roofs and is used for ALL roof applications. You would use butyl tape for windows and doors.

[chuckster57]

Originally Posted by BigTexRex

What you need is Dicor sealant--it's compatible with TPO roofs and is used for ALL roof applications. You would use butyl tape for windows and doors.

It’s industry standard to use butyl/putty tape under the surface that you screw down onto the roof, and then cover the edge and screws with the appropriate sealant compatible with the type of roof. I have yet to remove a vent or skylight that didn’t have the tape underneath.

[JRTJH]

I've never seen a factory or professional installation with DICOR under the edges. It's (as chuckster indicated) always putty tape or butyl tape under the screw lip and after installation on the roof, the screwheads and margins are covered with DICOR self leveling sealant. The only time I've ever seen DICOR under the screw lip is on an "owner installed component"....

[BigTexRex]

Originally Posted by chuckster57

It’s industry standard to use butyl/putty tape under the surface that you screw down onto the roof, and then cover the edge and screws with the appropriate sealant compatible with the type of roof. I have yet to remove a vent or skylight that didn’t have the tape underneath.

Thanks for the information...learn something new everyday.