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soohma 03-16-2018 10:59 PM

Type of caulk for outside of rv
 
I have a lot of caulk on the outside of my rv (1997) that I'd like to remove. It's turned dark and dirty looking plus there's a leak somewhere I need to find and fix.

I've read it's not good to use silicone caulk on the outside of a rv, so what type of caulk should be used. And any tips on using it will be appreciated. This is going to be a big job.

BBQ 03-17-2018 12:57 AM

.

NEVER never Never ever use household bathroom silicone
even if it says UV protected
even if it says it is for indoor/outdoor use


The silicone will fail, and it will be a pain-in-the-you-know-what to get it off
and you must get the old silicone off before you can apply a new sealant,
because most stuff do not adhere to cured silicone very well.

Use RV sealant
eg. dicor, butyl, etc.

peteco 03-17-2018 02:12 AM

I have used Lexel caulk for many years and am very satisfied. You can apply Lexel on top of itself. It is somewhat harder to work with than silicone so read up on how to apply and smooth. Do a search on reviews of Lexel and you will see many are hooked on Lexel.

soohma 03-17-2018 02:14 AM

Type of caulk for outside of rv
 
Thanks for the advice and especially for the names of the right types of caulk to use.
:flowers:

Davydd 03-17-2018 03:37 AM

Pure silicone won't fail and it will last 20 years or about 10 years more than most all other sealants. However, BBQ is right in that once down nothing will adhere and if you don't do it right, well, you have a mess on your hands. The problem is silicone is mixed with acrylics in a lot of consumer sealants and are no good. In fact stay away from any product using acrylics.

Rubber sealants don't last long and get brittle and hard. The best products are polyurethanes, one part or two parts, but again don't buy hybrids mixed with other products like acrylics and rubber. That is just a method to making them cheaper and probably sound good in marketing. Good polyurethane sealants are last about 10 years if properly installed. I don't keep up on product names anymore. I've been retired for 11 years. :)

BTW, sealant is the proper name. Caulk is a verb.

cruising7388 03-17-2018 03:57 AM

Quote:

Originally Posted by Davydd (Post 69279)
Pure silicone won't fail and it will last 20 years or about 10 years more than most all other sealants.

As long as we're on this subject, can you help me understand why the OEM caulking on every RV roof top I've ever seen looks like it's been dribbled on by a village idiot?

Davydd 03-17-2018 01:11 PM

Quote:

Originally Posted by cruising7388 (Post 69280)
As long as we're on this subject, can you help me understand why the OEM caulking on every RV roof top I've ever seen looks like it's been dribbled on by a village idiot?

OEM as in Mercedes, Ford, Ram or OEM as in Roadtrek, Winnebago, Advanced RV, etc.? I haven't seen any dribbling from the van manufacturers other than squeezed out of the seams sealant and I would guess they are pretty much assembled and caulked by computerized robots and I have heard not much about leaking in their assembly other than over 20 year old vans which have issues of just age. Nothing last forever. My MB doesn't have dribbled seams.

As for OEMs for the conversion, I doubt they are robots assembling things like skylights, AC, fans, vents, and other roof penetrations. you get what you get from humans and I think many of them think the more the better. I've had problems with all three of my Class Bs. Great West Vans skylight was the worst case in that the installer did not understand sealant should be placed in a continuous bead between the skylight frame and the roof. Subsequent repairs by a dealer didn't fix the problem and just wedding caked more sealant icing over it. I had to disassemble the whole skylight and start all over. I think I have an old thread here on the process.

Caulking is understanding the process and few employees are trained to understand what they are doing in that regard. Dribbles I guess are a way of seeing on inspection if the sealant is continuous and, of course, the belief the more the better. I know roofs are out of sight out of mind so no one seemingly cares about appearance.

On static buildings it is somewhat easier but you do get leaks mainly from just shoddy construction that mostly shows up right away. On moving vehicles you are not only dealing with wind pressures and climate but also different climates, moving parts with every bump in the road and metal, plastic and wood stressing and moving at different temperatures. Eventually you are going to have failures.

InterBlog 03-17-2018 01:28 PM

My favorite to date has been Sikaflex 221. It is difficult to apply and probably even more difficult to remove (I haven't had to try yet), but it seals very well. It was recommended by a well-known contractor who specializes in solar and lithium upgrades.

Reportedly per other forum threads, the company that produces it released another formulation more suited to RV applications, but I haven't tracked it down.

booster 03-17-2018 01:54 PM

Quote:

Originally Posted by InterBlog (Post 69283)
My favorite to date has been Sikaflex 221. It is difficult to apply and probably even more difficult to remove (I haven't had to try yet), but it seals very well. It was recommended by a well-known contractor who specializes in solar and lithium upgrades.

Reportedly per other forum threads, the company that produces it released another formulation more suited to RV applications, but I haven't tracked it down.

Do you recall what the tube or literature had to say about multiple coats, resealing, etc, adhesion? I ask because the place I used to work had always used PL urethanes with decent results, but a new engineer insisted that the Sika products were a lot better. When we tried them, we found they didn't stick to themselves well, similar to silicone products. I don't recall off hand which Sika products they tried, but it was all tube type caulking applications, outdoors in Minnesota.

Bud 03-17-2018 03:36 PM

Quote:

Originally Posted by peteco (Post 69277)
I have used Lexel caulk for many years and am very satisfied. You can apply Lexel on top of itself. It is somewhat harder to work with than silicone so read up on how to apply and smooth. Do a search on reviews of Lexel and you will see many are hooked on Lexel.

I am. Used it on the B and a house roof about 5 years ago. The roof gets Rain (metro New Orleans) and the Lexel sits under water for awhile in several areas. It was a new renovation with a new roof that was not warranted, another story.

Lexel is good stuff.

Bud

avanti 03-17-2018 03:55 PM

Quote:

Originally Posted by cruising7388 (Post 69280)
can you help me understand why the OEM caulking on every RV roof top I've ever seen looks like it's been dribbled on by a village idiot?

I think that question pretty much answers itself. :ermm:


For many purposes, butyl tape or Eternabond are much better choices than hand-applied beads of sealant. Guaranteed continuous and requires less skill. A role of 4" Eternabond is the swiss army knife of sealing.

cruising7388 03-17-2018 06:24 PM

Quote:

Originally Posted by avanti (Post 69286)
I think that question pretty much answers itself. :ermm:


For many purposes, butyl tape or Eternabond are much better choices than hand-applied beads of sealant. Guaranteed continuous and requires less skill. A role of 4" Eternabond is the swiss army knife of sealing.


Look at 4:03 to 4:21

https://www.youtube.com/watch?v=QzMldczZfMA

InterBlog 03-18-2018 01:31 PM

Sika 221 is one coat, sticks VERY well to everything it touches, and takes a very long time to degrade in any way. I also use it to seal the brick perforation where my air conditioner lines enter the house from the exterior condenser. People who live in the south know that area is an expressway for rodents. Normally it is packed with a sealing spray foam that they chew through and then they run up the lines to the attic. So far, knock wood, nothing has been able to chew through the Sika.

It is not self-leveling and has the consistency of a very sticky peanut butter. People use different techniques for applying it. Solar installer Lew Farber uses a nitrile glove and a specific finger technique. I took oil painting lessons in my childhood and I use a palette knife type of technique.

Sika 221 is also paintable. Here's an example pic I took yesterday showing one of our roof rack feet which was covered by Sika 221 and then painted over with Bus Kote reflective roof coating. Bus Kote is a latex product and I was initially very hesitant to add it to the Sprinter's metal roof, but it is standing up wonderfully (blog post here). The caulk job (blog post here) is about 15 months old and the paint is 11 months old. With the way Airstream installed this rack with its feet jacked up on the roof ribs, I have to be careful not to allow moisture to penetrate under the feet because it would rust out the sheet metal of the roof. Anyway, a year after this was applied, it shows no signs of degrading.

https://i.imgur.com/r6K1lH5.jpg


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