Roof sealant

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Jan 13, 2005
What's the best material(s) to use on/over roof-mounted screws or hardware? e.g. the roof mounts for my ladder are showing signs of the sealant starting to lift. I know I'm going to have to re-seal around the a/c units at some point and I want to mount some other hardware on the roof. What would you use for cable/wire entries?

Monaco recommends Acryl-R for all roof openings such as vents, skylights, roof mounted antennae and ladder roof mounts. They recommend Geocel 2300 where items are sealed under a painted surface such as the metal corners of slideouts. Are both these items available at hardware stores?

Duct seal works good for wire entries in to the house. As far as what i have used on the motorhome, I have used Butyl rubber from Ace Hardware. It comes in a tube like caulking and is pretyy easy to apply.  It comes in white which is good for the roof. I have used it on both of my motorhomes with goodluck so far. Hopes this helps.
Thanks Karl. I have a fiberglass roof.
Your a/c units probably have gaskets rather than caulk and they seldom leak anyway, no little to worry about there.

Most RV shops sell various brands of RV "roof caulk", including some with a "self-leveling" attribute that spreads nicely without you having to mush it into every cranny. Can't use self leveling caulks on vertical surfaces, though.  ::)

I use clear silicone on the fiberglass parts, e.g. around windows and the vertical seam on my front cap. The drawback is that nothing else sticks to the silicone - you have to remove it and clean thouroughly before you can re-apply it [or anything else].
I use clear silicone on the fiberglass parts, e.g. around windows and the vertical seam on my front cap. The drawback is that nothing else sticks to the silicone - you have to remove it and clean thouroughly before you can re-apply it [or anything else].

Thanks Gary. That's the only reason given by Monaco for not using silicone. OTOH when Monaco made a temporary fix of a small crack where the front cap meets the roof, they used clear silicone. Presumably they knew they would eventually be grinding the surrounding fiberglass away when they make the permanent repair  ;D

On the water I've used Boat Life Caulk, a polysulphide, for many years. Excellent adhesion, but also tough to remove.

I'll check out the self-levelling sealant, although that's not critical for replacing the "large blobs" that were applied over screws and hardware at the factory.

Right on about the a/c gaskets. Read somewhere in the Coleman lit. that caulking should NOT be used around the gaskets. IIRC, it had something to do with premature hardening/deterioration of the gasket and subsequent leakage and greater noise.
I'd made an assumption that the a/c units were caulked based on comments I'd read here earlier. If they're gaskets, I won't even bother to check them - probably best left untouched.

BTW I just called Monaco and confirmed the a/c seals are rubber gaskets.
The gaskets will compress with age and the mounting bolts need to be tightened periodically to prevent leaks.  When the bolts can't be tightened any further, it's time to replace the gaskets.
Thanks Ned. I guess I'm joust going to have to go up there and crawl along on my hands and knees.
On my previous RV, I could remove the A/C inside baffle cover and tighten up the bolt which compressed the seal. I did this every couple of years, just a little bit, as was recommended to me.

On my present Dutch Star I have ceiling and can't get to the A/C units. I asked about removing the ceiling and a Newmar tech said 'Don't try it! '.

So after 5 years plus I haven't tightened them. Just hoping I am OK.

I have not looked carefully at the units from the top, as to if they can be tightened but doubt it. I need to replace one of the exterior covers soon as its cracked a slight bit.

On the subject of sealing, I have been painting on the white stuff from Camping World around all the roof seams and vents once per year. I had one very slight leak at the shower cap and cleaned it all off to screw heads and used self leveling sealer and that worked fine.

My son replaced my five front amber running lights on top cap and he used Siraflex to seal the new ones. That is what Newmar recommends for callking seams, etc.

Next year I am going to do my entire roof seams and all around the vents with the new ethernabond tape.

Jim Godward has used this. Its somewhat easy to apply and is recommended by Newmar.

I have a fiberglass roof.


On many horizontal surfaces we use Lap Sealant. They make two types, one for rubber roofs and one for the rest. I find it works very well. I have used C-10 but it hardens and turns yellow. Will not be using that again. American Coach uses three different types for their coaches. The skylight in the shower uses a special sealant to prevent cracking. Be sure to check with Monaco to see if they have a similar requirement. My owner's manual lists the various sealants they recommend.
Thanks Jim and Bob. For clarification, I'm not trying to seal the roof per se, just trying to seal where new hardware (screws) will be installed and replace the "blobs" of sealant over the top of the ladder mounts on the roof. We had just washed the coach and I needed to check something on the roof. Since I don't do heights, my best way of getting onto the roof was on hands and knees directly from the ladder to the roof. Any attempt to stand would result in me feeling like I was about to keel over.

Now, that ladder is very narrow, especially when I'm trying to kneel on it, so my knees were effectively spreading the top of the ladder at the roof mounts. That's when I noticed water squishing out from under the sealant and the alarms bells started ringing.

It's still not clear to me if Monaco applies sealant to the screws themselves before inserting them. If so, I don't understand the purpose of the big blobs of sealant over everything. It seems to me that they merely mask whatever is going on underneath.

I guess I don't see how Eternabond would work over the feet of the ladder and several screws.
Tom said:

I guess I don't see how Eternabond would work over the feet of the ladder and several screws.

If I understand you correctly you are talking about where the ladder is attached to the roof.  If it were me I would clean up the area, reseal and then when sealant has cured I would apply narrow strips of Eternabond tape a short distans vertically up the ladder and lay it out where the end would lay on the roof over lapping each strip.  Hope this makes sense.
How about this? If the tape is wide enough, cut a disk large enough to overlap the ladder mount by 3/4' or so.  Then cut out the center of the disk to match the diameter of the ladder, with a single cut through the disk to the center.  Then form the tape around the ladder, covering the ladder end and the screws, bonding to the roof.

We use lap sealant over anything that attaches to the roof. The ladder will move slightly whenever someone is on it. You probably want a sealant that will flex to a degree without cracking. I believe lap sealant will do that. I would remove the screws, make sure everything is dry. Put the screws back in with sealant in the holes and then reseal the whole thing. Eternabond might work but I would use sealant as well. With Eternabond you want to be sure it adheres all around the edges. I've used that on the roof of the shed and it's just like new after two years. A friend used it all along the edge of the roof on his coach. Hasn't had a leak since. However, I've seen it used on the flat roof of a slideout on Cherokee trailer skylights. It always leaks because they don't get a good seal all around. It takes time and patience to get it right. Once done, you shouldn't have any more problems.

Be sure to check all of your sealant carefully. I had a leak in my main awning rail which damaged the interior wall. I could not find it but American Coach did when they removed everything to repaint the exterior. The shop manager told me to clean all the sealant with a product that contains mineral spirits. This cleans and softens the sealant so it remains flexible. I've been using a product called Cleanzeze.(sp?) It's used by auto painters to clean the surfaces prior to painting. I believe it even will remove remnants of silicone. When cleaning look very carefully for any black spots you cannot remove. This is usually dirt in a void and should be resealed as soon as possible.

I just re-sealed all my vents and skylight prior to my shoulder operation. Haven't been able to get back on the roof to check them but we had torrential rain for a couple of days and there were no leaks. Now I have to check all the mouldings.

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