Roof vent question

[LDK]

I'm about to install the roof vent but I am wondering what would be the best sealant to use. I have butyl tape and 3m 4200 or maybe I should use a good silicone caulk. I can't decide on what to use. Any advice would be appreciated.

[Loader]

Larry,

I used the tape (picked it up at a local RV dealer) on the Bungalette, and I plan to use it again on the current build. I had no problems with it at all.

[Synthesis]

I second the butyl tape.

On my teardrop, I installed a used Fantastic Fan. Since I have a plywood roof with EPDM Rubber roofing over it, I used the Butyl Tape between the rubber and bottom of the flange.

After it was securely screwed in place, I cleaned up the excess that compressed out. I then used an EPDM RV caulk to seal the heads of all of the screws and around the outer flange against the EPDM. It bonds to the roofing material and provides a tight seal.

[LDK]

Well I went ahead and used butyl tape on the roof vent. I applied it to the inner flange and then screwed it in place. I think it turned out pretty good.



I guess now I could hit each screw head with a dab of silicone.

[48Rob]

I guess now I could hit each screw head with a dab of silicone.

Larry,

After trimming off the excess putty tape, it is wise to run a (small) bead of sealant around the edges to protect the putty from drying out from being exposed to the elements, and to form a second barrier.

Applying a dab of sealant on the screw heads is a good idea, but a method that assures a better chance of no leaks is to remove the screws a couple at a time, inject sealer into the hole, then reinstall the screws.

The reason for the dab of sealer on the screw heads is to prevent water from following the screw threads into the wood.
By injecting sealer and reinstalling the screws, you have created a gasket/seal that won't allow any moisture to follow the threads, even if the screw head to flange area opens up.

Rob

[48Rob]

Larry,

You asked in a PM about what type of sealant; since it pertains to this thread I decided to answer here.

Silicone will work, but a polyurethane caulk is better.
I've been using another product that surpasses them both (in my opinion) which is a synthetic rubber and resin mix in a carrier.
It is called Micro gutter seal.

It works best when warmed up (very warm) as the warmer it is, the thinner the product becomes.
Thinner allows it to get into, and seal, very small cracks and holes.
I like it because it stays clear, doesn't attract dirt like silicone, and best of all, if you want/need to remove it, it will come back off leaving no residue.
(It is not easy to remove, but not impossible like silicone.)

If you are stuck on using silicone, give yourself the best chance of success by using mineral spirits, or better yet Acetone to clean all surfaces first.
Be sure your roof material won't be damaged by either before using.

(Silicone has gotten a bad rap from users who simply pump it out of the tube and fail to smooth it out with moderate pressure to assure good contact, or smear it on without properly preparing the surfaces first, then complain that it doesn't stick very well...
Much like painting your car without bothering to wash-degrease-and sand it first).

Whatever product you choose, if you inject sealer and reinstall the screws, be sure to retrim the putty around the edges before caulking them, and of course clean all mating surfaces with the solvent recommended by the manufacturer.

Rob

[LDK]

Thanks Rob.

[LDK]

Hey Rob

I remember you mentioning something about that sealant several weeks ago. I was going to get it but I couldn't find that particular one locally. I may just go ahead and order a tube of it on line and use it on all the exterior screws. If heating it up thins it out, that would work well in all the screw holes. It would pentrate deeper in the holes like you mentioned and that would be a good thing. I could use a syringe and inject it into the holes.

[48Rob]

Hi Larry,

Good thinking!
However, just cutting the tip of the tube very small, and using nothing larger than coat hanger wire to puncture the inner seal will allow the material to get far enough in the screw holes.
When you run the screws back in, they will force the sealant into every crack and crevice!

Rob

[LDK]

Hey Rob

I went to lowes today after work and I finally found this stuff. I thought maybe laying it in the sun for awhile would help to thin it out. What would be the best way to warm this stuff up? Also I wonder if it would have a reaction if it came into contact with the butyl tape.

[48Rob]

Hi Larry,

Lowes keeps it with the gutters...instead of with the caulk...

I've used it with butyl putty tape for several years and have had no adverse reactions.

I put mine on the dash of my truck in the sun, or in cooler weather, I turn the defroster on high for a few minutes till the tube feels very hot.

Rob

[LDK]

I'll definitely use this stuff in all the screw holes and around the roof vent. I used white 3m 4200 adhesive/sealant for the aluminum skin. I'm still gonna use the 3m 4200 for the trim too but now I can use the osi gutter sealer around the edges of the trim after it's installed for added insurance. Since it's clear, it should look ok.

[Loader]

Thanks for the info Rob!, I'll be picking some of the OSI up as well! Great questions Larry.