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Author Topic: Which sealant is best for roof leaks?  (Read 3727 times)
belfert
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« on: 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.
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FloridaCliff
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« Reply #1 on: 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
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luvrbus
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« Reply #2 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
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belfert
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« Reply #3 on: October 08, 2007, 11:46:37 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.
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« Reply #4 on: 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
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« Reply #5 on: 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
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« Reply #6 on: October 09, 2007, 05:44:06 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.

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Craig Shepard
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belfert
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« Reply #7 on: October 09, 2007, 05:59:08 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. 
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« Reply #8 on: 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
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belfert
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« Reply #9 on: 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.
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Brian Elfert - 1995 Dina Viaggio 1000 Series 60/B500 - 75% done but usable - Minneapolis, MN
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« Reply #10 on: 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
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« Reply #11 on: 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.
« Last Edit: April 28, 2013, 09:31:58 AM by belfert » Logged

Brian Elfert - 1995 Dina Viaggio 1000 Series 60/B500 - 75% done but usable - Minneapolis, MN
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« Reply #12 on: 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 Roll Eyes
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« Reply #13 on: 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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Scott & Heather
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« Reply #14 on: April 28, 2013, 01:22:42 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.
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Brian Elfert - 1995 Dina Viaggio 1000 Series 60/B500 - 75% done but usable - Minneapolis, MN
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« Reply #15 on: April 28, 2013, 01:25:00 PM »

I bought a quart of Elixir Plas-T-Coat some years ago for general roof stuff.  I have used it on seams and around roof penetrations.  It is a brush on product that is much thicker than regular roof coatings.  I do not know about Pro/Flex but assume it is something similar.  

When I bought the stuff on the recommendation of an RV repair place, they told me that the can would last indefinitely if I put a bit of water in it after finishing a use. That's what I have done, and it was still good the last time I used it about a year ago.  It is not water soluble, so the next time you use it, you just drain the water and your ready.
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« Reply #16 on: April 28, 2013, 05:47:19 PM »

You want to use a commercial grade roof sealant. The stuff I've got is Acrylic Urethane. It's made to seal roofs, move with the material (expansion/contraction) Paintable etc etc. They make it in white and it's paintable. Remove old caulk (theres some caulk remover stuff that works well, I prefer a sharp/thick putty knife), use some sand paper to clean the surface then mineral spirits. Perfect adhesion.

Then you should probably seal the WHOLE roof with a elastomaric coating (Kool Seal or something from home depot) Typically $20/gal but 5 gals are around $70. It seals and insulates. They even make a thick version that you slop on to cover bigger cracks/holes. Stuff has a 10 year warranty against leaks.
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« Reply #17 on: April 28, 2013, 07:09:38 PM »

Brian,

Someone from this board recommended to me CR Laurence 33S BL (Black) or C (Clear) and thats what I have been using.  Its been on the bus for about 10-12 months and it holds really well.  No cracks and is very flexible.  Not hard to work with.  Easy to wipe with towels.

I could not find it anywhere local and had to order it online.
http://www.crlaurence.com/crlapps/showline/offerpage.aspx?Productid=1036&GroupID=560&History=39324:330:511:524&ModelID=560

-Sean
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« Reply #18 on: April 28, 2013, 07:13:18 PM »

I don't know if I want to do a roof coating or not.  I've read lots of stories of the roof being hard to keep clean after putting that stuff on.  My bus is stored under trees and it hard to keep the roof clean as it is.  The roof paint is not in good shape now as the clear coat is coming off all over.
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Brian Elfert - 1995 Dina Viaggio 1000 Series 60/B500 - 75% done but usable - Minneapolis, MN
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« Reply #19 on: April 28, 2013, 09:28:58 PM »

Polyurethane and latex on the roof will dry out and turn to dust (on my truck conversion, they used polyurethane sealant on the roof, and after just 3 years, was leaking. I wire brushed it off the resealed with outside gutter silicone). I used silicone on my bus around my vents. That was 18 years ago and it is still rubbery and no leaks. Exterior grade of silicone (the type that smells) is still the best sealant. Good Luck, TomC
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« Reply #20 on: April 29, 2013, 11:57:40 AM »

I used the 3M flexible seam sealer a few years ago.  It was really difficult to be neat with it. I end up using my finger to apply it.  The warmer the better.  It fixed every leak and its paintable.  I painted over it with the white rubber roof paint and done!   No leaks, looks good, great product.  Not cheap though.  $44 for a 1/4 gallon. 
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« Reply #21 on: April 30, 2013, 05:59:04 AM »

I used a block foundation sealer on mine It was blue when applied but its paintable. I painted gloss white. Very similar to the stuff that you dip tools in for rubberized handle great stuff. Found it at a big box store Five plus years holding up great


Rick
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« Reply #22 on: April 30, 2013, 07:45:35 AM »

There are a lot of options on roof sealing.  I think I'm going to try the stuff Clifford recommended.  I am placing an order tomorrow with Tweety's so I'll add the sealer to my order.  Will that ProFlex sealer work around my Transspec roof hatches?  The hatch frame is held down by screws going down into the steel framework of the roof.  The screws weren't really sealed at all when I got the bus and I'm sure they were leaking.

Will chip brushes work with the ProFlex sealer or do I need to step up to cheap brushes with plastic bristles?  I have a whole box of chip brushes I bought some years ago.
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Brian Elfert - 1995 Dina Viaggio 1000 Series 60/B500 - 75% done but usable - Minneapolis, MN
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« Reply #23 on: May 01, 2013, 07:44:34 PM »

This is another one you might try, it even mentions trucks and buses in the spec sheet.

http://www.tremcosealants.com/products/trempro-635.aspx

HTH
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« Reply #24 on: May 02, 2013, 02:16:14 PM »

I ordered the ProFlex RV sealer.  Can I use chip brushes with this stuff?
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Brian Elfert - 1995 Dina Viaggio 1000 Series 60/B500 - 75% done but usable - Minneapolis, MN
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« Reply #25 on: May 02, 2013, 05:31:24 PM »

I used the 3M flexible seam sealer a few years ago.  It was really difficult to be neat with it. I end up using my finger to apply it.  The warmer the better.  It fixed every leak and its paintable.  I painted over it with the white rubber roof paint and done!   No leaks, looks good, great product.  Not cheap though.  $44 for a 1/4 gallon. 

OneLapper,

Also used the seam sealer on mine, hard to believe 6 years ago (2nd post in thread) and it has held up great, no leaks.

Knowing it has no adhesive issues with paint is a big plus.

Cliff
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