Resealing the roof vents - new hardware?

[ShrimpBurrito]

I’m about to reseal both the Fantastic Fan and the non-powered roof vent. I’m going to replace the risers, which I have learned are made of recycled plastic lumber, since they are broken apart along where the factory used staples. Even the replacements from the factory are made that way, sandwiching a thin layer of caulk in the seal that just rubs right off (and thus has near zero adhesion, and little sealing properties). I’m going to cut new risers out of PVC and glue them together to create a strong watertight seal, and put a stainless screw into the SIDE of each corner for additional strength. The factory puts staples on the bottom and top, and they’re not flush with the riser, and so I imagine that makes for a less than perfect seal (but obviously it’s “good enough”, at least for awhile).

Other than that, does any of the other hardware need replacing? Or should it be replaced? The Vent flange is going to have to be cleaned at least, and I have no idea if that will be a difficult job or not. Has anyone here felt the job would have been much easier with a new vent or flange? I’d consider a new vent (about $50) if it were going to save me a lot of work, but not a new fan due to cost and because there’s nothing wrong with it.

For the reinstall, as I’ve read in some other threads, I’m going to put down butyl tape on the roof, then the riser, then another layer of butyl tape, then the vent, and then self-leveling lap sealant. Any recommendations to the contrary?

Many thanks,
Dave

[Larryjb]

Dave,
I just finished replacing my vents.

I also replaced the vinyl risers and I found some vinyl trim from Home Depot that almost perfectly matched the size of the original risers. I used PVC cement, then inserted several brads into each corner.

I opted to use the EZ-Vent simply because it uses a clamp style rather than screws from above. My personal feeling is that the fewer holes you have on top the less chance of leaks. The downside of this is that their fan isn't as good.

As for the Fantastic Vent which must be screwed from above, I think the most important thing is to make sure you put some non-silicone based sealant into each hole. I use Proflex RV because it seems to remain soft is relatively easy to remove, and doesn't need to be removed completely when resealing. I did use the butyl tape under the riser, and two layers of butyl tape the vent itself. This is the same stuff used around the windows and seems to seal well as long as it is clamped or screwed. I then added one more bead of RV Proflex around the perimeter at the base of the riser and around the perimeter of the vent itself.

When I removed the old vent, I saw remnants of the old sealant. I believe a previous owner had removed the vent and used silicone. This stuff just leaked like a sieve. A couple of years ago I had used Eternabond as a temporary measure until I could fix the sealing properly. I discovered that despite my efforts to get a good seal all the way around, it did not make a good seal in a couple of places which allowed it to leak pretty badly. I wouldn't bother with Eternabond around the vents. It may be fine for the long seam, but it has been a fail in my books around the vents. You may think it's not leaking, but what happens is that it leaks through the screw holes, then down between the styrofoam and aluminum so you never see the water. But then it can sometimes find its way behind the walls and rot out the the wood veneer wall behind the kitchen, or find another point of entry through one of the lights. Eternabond is also nasty to remove in the future.


The only method of sealing that has worked 100% for me is to sandwich a sealant (like RV Proflex or butyl tape), and make sure you squeeze some Proflex into each hole.



I also checked the condition of the wood frame inside the roof. Mine was okay still, but I used some Zinsser 123 primer on the wood. I checked the condition of the bond between the wood frame and aluminum. I glued and clamped portions where the glue had failed with some Gorilla glue.

I haven't seen any evidence of leaks and we've had some pretty good rain storms, so I think it is good.

[rickst29]

for driving down all of my screws on the max-air, it seems to be a good idea to seal the threads with *something*.

[Larryjb]

To summarize sealant fails in my trailer:

1) applying sealant to the tops of screws. (by previous owners, and was a BIG fail).
2) applying sealant around the perimeter of anything. (by previous owners, and was a BIG fail.)
3) use of Eternabond. Any imperfection in the surface or fold or kink in the tape as you are applying it will leak. Another BIG fail for me. (Seems to be fine on long seam where there is little risk of kinks or folds.)

[ShrimpBurrito]

Thanks, Larry and Rick. What did you both use between both sides of the riser and the roof and vent?

Larry, you mentioned “putty”, which I first assumed to simply be butyl tape, but you said that failed in your subsequent post.

Dave

[Larryjb]

Originally Posted by ShrimpBurrito

Thanks, Larry and Rick. What did you both use between both sides of the riser and the roof and vent?

Larry, you mentioned “putty”, which I first assumed to simply be butyl tape, but you said that failed in your subsequent post.

Dave

Ah, I'm confusing Eternabond with butyl tape. Yes, I used butyl tape between the roof/riser, and vent/riser. Then I used RV Proflex around the perimeters.

NOTE: I have corrected my previous posts.

Butyl tape = good
Eternabond = not so good for vents.

[ShrimpBurrito]

Excellent, thanks for the clarification, Larry.

Dave

[rickst29]

Clarification: So I didn't do anything to the square riser's original seal against the roof (done with screws or staples, I guess). But I did add a thin layer of P&L 'marine fast-cure adhesive/sealant' (a cheaper generic version of 3M '4200', from Home Depot) along the edges of the fan mounting plate, as well as adding it into the threads of supplied SS mounting screws.

When driving the screws down, some of the adhesive was driven back up to the screw head - and I left it there, assuring complete coverage. Your riser replacement is a way bigger job. Neither TM or owners doing riser replacement would leave it attached with only "boat sealant", a stronger fastener would seem necessary (to me). The butyl tape seems like a good option for that job, avoiding the issue of orginal staples working loose.

[Larryjb]

Originally Posted by rickst29

Clarification: So I didn't do anything to the square riser's original seal against the roof (done with screws or staples, I guess). But I did add a thin layer of P&L 'marine fast-cure adhesive/sealant' (a cheaper generic version of 3M '4200', from Home Depot) along the edges of the fan mounting plate, as well as adding it into the threads of supplied SS mounting screws.

When driving the screws down, some of the adhesive was driven back up to the screw head - and I left it there, assuring complete coverage. Your riser replacement is a way bigger job. Neither TM or owners doing riser replacement would leave it attached with only "boat sealant", a stronger fastener would seem necessary (to me). The butyl tape seems like a good option for that job, avoiding the issue of orginal staples working loose.

TM does not secure the riser to the roof with screws or staples. It is held in place by either the clamping force or the EZ Vent or the screws used for other vents.

The only issue I have with your method of sealing around the perimeter only is that it is very easy to miss a spot. Visually it can look fine, but there can still be a pinhole leak. Maybe it's my technique, I don't know.

The riser doesn't have to be replaced if it is in good condition. The only reason I replaced my riser is that it was cracking apart after years of exposure. If the previous owner had used butyl tape, and I had not used Eternabond, and if the riser did not need replacement, removing the vent and riser and replacing the butyl tape wouldn't have taken much longer than what you did. In your case, because you removed the screws, the vent was probably ready to lift off at which time you could lift the riser off, replace the original butyl tape, slap the riser back in place, add sealant to the screw threads as you did and secure the works back to the roof.

However, if your method keeps it sealed, that's good. Perhaps the trouble I had was the residual silicone that the previous owner used which prevented a decent bond of anything else. I think I would have to say that if some one had used silicone, you would probably have to lift the works off to clean it up and sandwich new butyl tap in there.

-----------------------

Perhaps as a hybrid method, you could loosen the screws so that the riser can lift up a little, apply your marine sealant all the way around, oozing it between the riser/roof and vent/riser, then resecure the screws. Just a thought.

Anyway, what ever works. My previous owner said he recaulked everything by going around the perimeter and on top of all the screws. A few months later on a trip to Kamloops, was water leaking everywhere, so his job didn't do anything.