# Dicor I Just Added Is Cracking. Why?



## Stance

I just spent a ton of time caulking the OB. Everything looked fine afterward. Most of the caulk I applied sat for at least a day or more before we left. When we got to our destination, I noticed roughly half of the caulking had cracked. It is a single, long crack in the middle of the caulk along the joint. I used Dicor non-sagging. The first time I put it on, I put it on thin to keep it neat. It cracked. So, this time I put it on thicker (not too thick), and it cracked. Should I use something else? The joints were cleaned well before applying it.

Also, Dicor doesn't stick to what I am assuming is silicone caulking the factory uses. Peels right off.


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## CamperAndy

If this is for side lights or trim then you need to use a silicone caulk.

I only use the Dicor for the roof fittings and then use the self leveling version. It can get surface crazing but it seldom has deep cracks.


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## Stance

Yeah, lights, trim, speakers, etc. I had the kitchen window leak. That Dicor caulk is still good for now.

Figures. I thought I read on here that is what people recommend. I guess I misunderstood.

1. Any recommendations on how to remove it cleanly?
2. Do you have a favorite silicone caulk?


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## CamperAndy

Windows use Butyl rubber tape for the flange when they are installed new. Not normally needed to apply any additional sealant.

To remove Dicor, use a heat gun and a plastic scraper. Use only enough heat to get it soft then it should come right off.

I always use latex caulk. Water clean up means that if I screw it up it is easy to clean off and re apply. If you use the non latex it may last longer but it is an art to get it to look good.


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## duggy

I use GE silicone around lights, etc. Make sure that the silicone smells like vinegar. If it doesn't, it's not the right stuff. GE also makes a product called Silicone II. I don't recommend it. As Camper Andy said, it's an art to apply, but it's what was used in the first place, and stands up the best. Make sure the surfaces are thoroughly clean first.


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## TennesseeOutback1

To help apply the silicone I always have a small cup of water and a paper towel. I speed the silicone then wet my finger and gently, in the same direction as applied, smooth it out. I hope I explained that well enough. Always make sure your fingers is wet that way the silicone wont stick to your finger.


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## SDCampers

No ya all have me confused. A while back I read on here that silicon caulking doesn't stick well to the fiberglass and to use a non silicone caulk. has this changed?


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## CamperAndy

SDCampers said:


> No ya all have me confused. A while back I read on here that silicon caulking doesn't stick well to the fiberglass and to use a non silicone caulk. has this changed?


There are few basic different types of silicone, Latex, Acrylic, and Silicone oil based (there may be a better word for the oil based stuff but I can not think of it at the moment). They all will stick to fiberglass but may not stick to the rubber roof. I prefer to use the Latex based silicone as it cleans up with water, the oil based requires mineral spirits. The oil based is reported to last longer but I do not think that is a good enough reason to use it since even the shorter life stuff will most likely out live the trailer.


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## CamperAndy

Truth be told there are so many different combinations of caulking compounds that it is hard to keep up.

I just went and looked at what I used last and it was a Acrylic Latex Silicone Caulk, I guess it covers all bases.

Anyway pick a water based product with a long life (typ 10 to 15 years) listed on the tube and you will be just fine.


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## Stance

CamperAndy said:


> No ya all have me confused. A while back I read on here that silicon caulking doesn't stick well to the fiberglass and to use a non silicone caulk. has this changed?


That's what I remember. I remember reading that others have used Dicor instead. After reading Andy's first reply, my wife and I remembered the dealer telling us during the PDI to use silicone caulk which we inconveniently forgotten until reading Andy's post.

Oh well, I guess it's another one of life's lessons learned the hard way.


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## therink

From my own experience silicone products do not last or adhere well in the outside elements to plastic, fiberglass or aluminum. 
I highly recommend using only urethane based caulk made specifically for rv's. Dicor and ProFlex are two good names. You will need to use lap sealant around windows and other vertical seams. Use self leveling Dicor on the roof. 
Generally, these products are not available in home stores. Any rv supply store will carry them, also Google the brands to get cheaper online. 
Using dish soap on the finger when working urethane caulk is very helpful. 
Steve


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## Stance

Are you talking about this stuff?

Dicor Lap Sealant - CW

That is the stuff I used and a majority of it either peeled and/or cracked within days of applying it. If it isn't the stuff you mention, do you have a link to it?

Thanks.


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## therink

Stance said:


> Are you talking about this stuff?
> 
> Dicor Lap Sealant - CW
> 
> That is the stuff I used and a majority of it either peeled and/or cracked within days of applying it. If it isn't the stuff you mention, do you have a link to it?
> 
> Thanks.


Where on the RV did you apply the lap sealant?


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## clarkely

i will chime in as well ........... I use Dupont Corian adhesive silicone - i was looking online to provide a link for it ..... i can find a bunch of there silicone's but not the one i use ... it may only be available for fabricators (we sell to them) but if you have a local shiop to you......that stuff is an adhesive and silicone like no other.......... expensive, but extremely strong and yet flexible to take an rv's constant movement.......


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## Stance

therink said:


> Where on the RV did you apply the lap sealant?


Around the windows, trim, lights, speakers, etc. The stuff around the windows was OK before I put it back in storage. A lot of the other caulk pulled away and/or cracked. I used self-leveling Dicor on the roof and it seems to be holding up well.


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## Stance

Follow up: I tried using Lexel clear caulk to replace most the Dicor I applied. It didn't seem to want to stick to the existing silicone when applying it. Also, since it was so clear, I had a very hard time seeing if I had enough applied.

So, I then tried using GE Supreme Silicone caulk (100% silicone). I chose it because it stated it was shrink and crack proof. It also stated "Extra Flex" claiming it flexed 50% more than other caulks. I am very impressed by it. It spread like butter and cleaned up pretty easily. I could clean it off my fingers with just paper towel if I didn't wait to long. It is gloss white and blended in with the fiberglass very well. It seems to be sticking to everything very well so far and no cracks or pealing edges (knock on wood). I am very happy with it.

Interestingly, I applied some of it to some over the Dicor I applied to see what would happen and it is still sticking well. It's odd that it will stick to Dicor but Dicor will not stick to silicone.


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