My 5th wheel is 5 years old and despite sitting out in the Texas sun I have no issues with any leaks in the roof. To that end, I feel it's time to do a little preventive maintenance so I've got a tube of Dicor self leveling caulk and I'm getting ready to touch up.My question is: should I try to remove any of the old calk on the roof, or just apply a light coat of the Dicor over the existing calk?The local RV dealership service department recommends not trying to get any of the old stuff off as one might cut into the rubber roof. I feel I can be gentle enough using a piece of plastic to at least get some of the old calk off without damage to the roof. The problem I see in applying more calk on top of the old is that it will build up the existing seams and create an area that will be a "dam" and hold water. What do you think?

Wash the roof then clean the area to to be calked with alcohol, dry and calk.

dryfly wrote:My question is: should I try to remove any of the old calk on the roof, or just apply a light coat of the Dicor over the existing calk?NO and yes to the light coat. All you want to do is seal any cracks that might be appearing in the old caulk. Do a two foot section at a time. Lay a thin bead, then smooth a little with a plastic spoon. It will self level real well after that.

If you're talking about seams, I would skip the caulk and go with EternaBond. Do the job once then forget it. That stuff will outlast you.

Only remove caulk that has failed and is loose and pealing up. Otherwise just touch up cracks and areas that look deficient. Wipe clean with a wet rag, let dry, then apply new Dicor generously. Don't try to go over all areas that look perfectly good. Just hit the bad spots.

If the old caulk is still pliable, and stuck, don't do anything.But yes, any cracking or obvious bad spots, clean and Dicor.

Re-sealing roof with Dicor | Good Sam Community

CA_Traveler
Explorer III
Feb 15, 2015
Wash the roof then clean the area to to be calked with alcohol, dry and calk.
John_Joey
Explorer
Feb 15, 2015
dryfly wrote:
My question is: should I try to remove any of the old calk on the roof, or just apply a light coat of the Dicor over the existing calk?

NO and yes to the light coat. All you want to do is seal any cracks that might be appearing in the old caulk. Do a two foot section at a time. Lay a thin bead, then smooth a little with a plastic spoon. It will self level real well after that.
ed6713
Explorer
Feb 15, 2015
If you're talking about seams, I would skip the caulk and go with EternaBond. Do the job once then forget it. That stuff will outlast you.
time2roll
Nomad
Feb 15, 2015
Only remove caulk that has failed and is loose and pealing up. Otherwise just touch up cracks and areas that look deficient. Wipe clean with a wet rag, let dry, then apply new Dicor generously. Don't try to go over all areas that look perfectly good. Just hit the bad spots.
RJsfishin
Explorer
Feb 15, 2015
If the old caulk is still pliable, and stuck, don't do anything.
But yes, any cracking or obvious bad spots, clean and Dicor.
Snowman9000
Explorer
Feb 15, 2015
The spots that are dammed will always need you to keep an eye on them. But if you maintain the roof, you should be okay.

You can really clean the old caulk well with lacquer thinner on a rag. Wear gloves, and don't get it on the rubber roof. If you do, wipe it right off. It won't hurt the roof in just a few seconds. Be careful of the can itself dribbling onto the roof when you set it down! BTDT.
Cloud_Dancer
Explorer II
Feb 15, 2015
Why do people keep using such a product as self-leveling Dicor? It seems to me that its failure rate is quite high, and for obvious reasons....IMO. I frequently see it used in applications where it makes no sense. IMO whenever you have a lap joint, you can bet there's going to be some movement, even if you don't see anything move. It makes a lot more sense to use a healthy bead of really good sealant, like 3M 4200 marine which has excellent qualities, right at the line of the joint. Then, cover the whole lap joint with 4" EternaBond, screw heads and all. And, replace screws with stainless while you have the joint exposed.
John_Joey
Explorer
Feb 15, 2015
Cloud Dancer wrote:
Why do people keep using such a product as self-leveling Dicor? ...

Same reason the maker of the coaches do. Last 10-15 years, reasonable priced, and isn't labor intensive.

The Dicor failure rate is on coaches that are not maintained and the roof is 10-15 years old. Cracks have formed and water got deep enough to get under the caulk.

On a 10-15 year old coach does it really make sense to put a 30-40 year repair job on? That RV may only last another 5-15 years. JMO
spadoctor
Explorer
Feb 15, 2015
IMHO from personal experience...forget Eternabond its junk
Cloud_Dancer
Explorer II
Feb 15, 2015
John&Joey wrote:
Cloud Dancer wrote:
Why do people keep using such a product as self-leveling Dicor? ...

Same reason the maker of the coaches do. Last 10-15 years, reasonable priced, and isn't labor intensive.

The Dicor failure rate is on coaches that are not maintained and the roof is 10-15 years old. Cracks have formed and water got deep enough to get under the caulk.

On a 10-15 year old coach does it really make sense to put a 30-40 year repair job on? That RV may only last another 5-15 years. JMO

Here's the problem, the water does NOT get under the Dicor self-leveling caulk. And, neither is this caulk water soluble. What actually happens is that this caulk cracks right at the seam line, and the water gets all the way under the roof to the inside. IMO this Dicor product gets rock hard and its bond is so good that it takes forever to get it off (hammer and chisel). But, if you leave the caulk on and just "V-out" the caulk down the seam line and then fill the groove with 3M 4200 marine sealant,....it'll form a dam for the water to collect.
BTW down here in the sunbelt, Dicor self-leveling caulk cures rock hard and cracks in just 2-1/2 years. I certainly would never ever use it.
If I had to fix a rubber roof, I would replace the entire roof, and then fix the joint around the perimeter MY WAY.

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