Which sealant is best for roof leaks?

belfert · October 08, 2007, 11:06:28 AM

My bus leaked liked a sieve when I first got it. There are various seams, open pop rivets, and such on the roof that had deteriorating sealant. Craig Shephard looked at my roof and recommended polyurethane caulk to seal everything up.

It has now been at least a year since I sealed things up and the problem is the polyurethane caulk is cracking in spots. It is good stuff, but I don't think it likes the flexing of the bus. I also used inexpensive latex caulk to seal the large roof hatch at the rear of the bus that was formerly used for accessing the A/C evaporator. The latex caulk is cracking in spots similiar to the poly caulk.

What do folks recommend to redo this? I know RVs use Dicor lap sealant, but is it paintable? Also, every lap sealant application I see on RVs looks like crap, but that may be because the application is done in a hurry. I would need a different sealant for the rear of the bus where the evaporator hatch extends down the rear of the bus.

I'm strongly considering Eternabond tape over the seams, but not sure how it would look. There is a paintable version instead of the white plastic/rubber version used on RVs. Since the roof is white now and I will probably repaint the roof white it may not matter.

FloridaCliff · October 08, 2007, 11:16:35 AM

Brian,

I used 3M sealant #08500 All Around Autobody Sealant

http://3m.hillas.com/pc-15426-1233-3m-08500-all-around-autobody-sealant-110-gal-cartridge.aspx

Works good, no repeat leaks on seams.

Cliff

luvrbus · October 08, 2007, 11:27:49 AM

Belfret, if you will look at bestmaterial.com they have about everthing to repair leaks and they have the best price on the eternabond tape 50' rolls

belfert · October 08, 2007, 11:46:37 AM

Quote from: luvrbus on October 08, 2007, 11:27:49 AM
Belfret, if you will look at bestmaterial.com they have about everthing to repair leaks and they have the best price on the eternabond tape 50' rolls

Thanks. This is the place I would probably get the Eternabond tape if I go that route.

Christyhicks · October 08, 2007, 07:45:26 PM

Well, I have to tell you, the best sealant we've ever seen is called "Through The Roof" caulk. I swear, it is the stickiest stuff I've ever seen. . . if you get a little on your fingers, then rub it on your pants, pretty soon, everything around you will be sticky too! It stays flexible and sticks like heck!

We use it any time we're going to set an a/c package unit on the roof, or seal a flashing. You can buy it in caulking tubes, or spreadable in cans. We found it in the roofing section of one of our local hardware stores and have used it for probably 10 years now.

Now, of course, this is applicable for specific small leaks, but it would be awfully expensive to coat a large area with it. Christy Hicks

Jerry32 · October 09, 2007, 02:52:10 AM

I put eternabond tape on mine as the local surplus guy had cases of it for $12 a roll. some of the instructions that came with the tape says you can paint over it. Jerry

gumpy · October 09, 2007, 05:44:06 AM

Quote from: belfert on October 08, 2007, 11:06:28 AM
Craig Shephard looked at my roof and recommended polyurethane caulk to seal everything up.

Did you clean the old caulk out and make sure the channel was clean before you put the poly in last time? It won't stick if there's any
dirt or debris in there, and it will shrink away then.

belfert · October 09, 2007, 05:59:08 AM

Quote from: gumpy on October 09, 2007, 05:44:06 AM
Quote from: belfert on October 08, 2007, 11:06:28 AM
Craig Shephard looked at my roof and recommended polyurethane caulk to seal everything up.

Did you clean the old caulk out and make sure the channel was clean before you put the poly in last time? It won't stick if there's any
dirt or debris in there, and it will shrink away then.

I cleaned everything with a very agressive wire wheel in a grinder. The wire wheel would remove all of the paint and start eating away the aluminum if I wasn't careful.

DavidInWilmNC · October 09, 2007, 07:10:46 AM

It's strange that it's not worked for you. I use polyurethane caulk / sealer for just about everything I need to seal or glue. I used some to repair a pair of tennis shoes this past weekend. It lasts longer than the shoes do. I generally use the black kind that's sold at Lowes as flashing sealer. It's the messiest stuff I've ever worked with, and Iit's ruined many clothes. Oh, and definitely wear gloves! When it's cured, it's extremely elastic and very hard to cut or trim. Perhaps the stuff you used was from a bad batch, but polyurethane sealers / caulks are the best I've found. I generally apply a decent sized bead of the sealer, then smooth it down with a pop sickle stick, if it's in a place where it will be seen. I've not found latex caulk to last long, especially when exposed to a lot of sun. It's not the best sealer, either (it hardens). It sounds like the stuff I use is similar to the what Christy's talking about.

David

belfert · April 28, 2013, 08:54:31 AM

I started this thread a long time ago and never did get up on the roof and recaulk the seams.

Are there any updated recommendations on products to use? I've now got a few leaks and really need to take care of this. Is the 3M 08500 still a good product to use. I can get it from NAPA to at least try out.

luvrbus · April 28, 2013, 09:08:30 AM

For your needs the Pro/Flex brush able is the best way to go good stuff unless you prefer the caulking guns and a clean up mess

good luck

belfert · April 28, 2013, 09:29:18 AM

I'm just trying to fill seams. I could be totally wrong, but isn't squeezing something out of a gun less messy than trying to brush something out of a can into a seam? I'm certainly willing to give it a try if it will really seal better than caulk from a caulk gun.

Are you talking about the regular Pro Flex or the Pro Flex RV? It looks like the RV stuff might be better suited for use on metal.

luvrbus · April 28, 2013, 10:24:46 AM

I find it easy just throw away the cheap brush I used, my first experience with Pro/Flex was at a Prevost center I watched for awhile and bought me a qt right now I am redoing all the years of built up caulking on the wife's RV some of it was 2 inches thick not anymore

Scott & Heather · April 28, 2013, 12:54:53 PM

FYI, we used poly caulk too and hated it. Cracked around every clearance lamp.

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belfert · April 28, 2013, 01:22:42 PM

Quote from: Scott Bennett on April 28, 2013, 12:54:53 PM
FYI, we used poly caulk too and hated it. Cracked around every clearance lamp.

That is my problem with the poly caulk. It cracked all over. I used poly caulk to fill some joints in my concrete sidewalk at home and it didn't adhere very well. I probably should have used backer rod for the sidewalk as the seams were wide.