Does Silicone work on the exterior?

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Dean_Reynolds

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My storage boot is leaking. Whenever we get a heavy rain, the gutter system of the trailer runs all the water down the front side walls… right over the under bed storage boot.

The old caulking there has since cracked shipping the water through the coach floor.

Would silicone hold up to the wind of driving? Or I have an older tube of dicor roof lap sealant. Is one any better than the other?
 
Henry's Tropical Roof Caulk is 100% silicon, but if I had Dicor that's what I'd prefer. You'll be lucky if an old tube of caulk hasn't hardened up. I'd remove as much of the old caulk as possible.
 
One major problem with silicone is you cannot put new silicone over old. It will not adhere.
There are better sealants available. Geocell Pro Flex is one. Don't understand your term 'storage boot'. Are you talking about the side access hatch? Post a picture of what you mean.
 
Just so you know there are two types of Dicor. One is self leveling used on horizontal surfaces like a roof and the other is for vertical surfaces
 
Silicone will work but you'll eventually regret it. It's a booger to remove.

I learned this lesson the hard way.
 
Silicone is crap your Grandad used. I don't ever use silicone anywhere, there are too many better options depending on where you need it. Dicor or pro-flex is what I have used for years. As always, surface prep is 90% of the repair.
 
Insasmuch as I've had excellent success with silicone in numerous outdoor applications over the years, there are "better" sealants. Think "marine grade" where the environment is brutal and the stuff has to work. I am not a fan of dicor because it has to be continuously renewed, though it does get points for ease of application and penetration. 3M 5200 is one and done, 3M 3000 is more silicone like but also very durable. Per above, the surface prep and proper application of any sealant is going to make or break it's success.

Mark B.
Albuquerque, NM
 
Mark_K5LXP said:
Insasmuch as I've had excellent success with silicone in numerous outdoor applications over the years, there are "better" sealants. Think "marine grade" where the environment is brutal and the stuff has to work. I am not a fan of dicor because it has to be continuously renewed, though it does get points for ease of application and penetration. 3M 5200 is one and done, 3M 3000 is more silicone like but also very durable. Per above, the surface prep and proper application of any sealant is going to make or break it's success.

Mark B.
Albuquerque, NM
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Be really careful using 5200 in this application. When they say that stuff is permanent, THEY MEAN IT. There are much better options that won't cause you heartache when it comes time to service.
 
Never use 5200 to run a bead that's going to be exposed. It does not like sun. You are wasting your money and time. But never run a bead of straight caulk over old caulk. If you think your leak is on any access hatch, remove it completely and start over. If it was somewhat bedded with silicone, it will come out with a little effort. Clean up and reinstall using 100 percent silicone.

Then run a bead around the perimeter if the exterior of your unit is the uneven metal skin. Of course this is just my opinion and no one or any interior wall has been harmed with the method for any rvs for me.
 
Jayflight said:
Never use 5200 to run a bead that's going to be exposed. It does not like sun. You are wasting your money and time. But never run a bead of straight caulk over old caulk. If you think your leak is on any access hatch, remove it completely and start over. If it was somewhat bedded with silicone, it will come out with a little effort. Clean up and reinstall using 100 percent silicone.

Then run a bead around the perimeter if the exterior of your unit is the uneven metal skin. Of course this is just my opinion and no one or any interior wall has been harmed with the method for any rvs for me.
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The 3M 5200 pdf doesn't say that, where are you getting that information?. Both, Dicor self leveling ( for horizontal applications) and non self leveling ( horizontal and vertical) sealants are perfectly fine being applied over existing Dicor sealants, just clean it first. Dicor is designed to be applied in layers.
 
Dean_Reynolds said:
Would silicone hold up to the wind of driving? Or I have an older tube of dicor roof lap sealant. Is one any better than the other?
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Yes it would, and pure silicone works fine for small beads around trim. Most RV makers use it around window trim, for example. The drawback is that you have to remove the old before applying any new, even a small patch. That's easy enough if its a bead against a flat surface, but a real bear if its corrugated or recessed.

Dicor lap sealant is almost surely the self-leveling variety, so unsuitable for any vertical surface. It will literally run down the sides. There is a version of the Dicor for vertical use, but its not in common use.

There are other excellent sealers for around windows & doors and it doesn't have to be an "RV" product. Most any window & door sealant from your local hardware of home store will do nicely, including those that are "silicone blends". Geocel Proflex is another excellent choice.
 
Onyrlef said:
The 3M 5200 pdf doesn't say that, where are you getting that information?. Both, Dicor self leveling ( for horizontal applications) and non self leveling ( horizontal and vertical) sealants are perfectly fine being applied over existing Dicor sealants, just clean it first. Dicor is designed to be applied in layers.
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Real life experiences, ask any boatyard that you trust to tell you the truth. If you are running a bead of caulking, you want any caulking to stay put. Dicor goes over existing dicor as long as you clean it and want it to stay long term. But an access hatch, which is sounds like he is dealing with should be dealt with in a diferent manner. All you are doing by just applying over old stuff is masking an issue. YMMV
 
Bonding issues depends on the silicone type.
However as others have said I would use a fresh tube of rv related sealant made for that purpose.

What is the difference between acetoxy and neutral cure silicone?

*** As acetoxy cure silicones release acetic acid whilst curing they can cause bonding/discoloring problems when used on certain substrates.

When used on natural stone they can cause discolouration, when used on certain metals they can cause corrosion and on bituminous surfaces they can cause "bleeding" of the bitumen.

So when applying sealant to sensitive surfaces we would always recommend using a neutral cure silicone over a acetoxy silicone as they will not react.

Generally acetoxy silicones are used for kitchens, bathrooms and other internal sealing applications as they are more cost effective and faster curing than their neutral curing counterparts.

Whereas neutral cure silicones have better adhesion and weatherproofing properties compared to acetoxy silicones making them the superior option for external applications.***
 
Ray-IN said:
There is a reason Silicone sealants are the cheapest on the shelf.
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Actually there are several levels of marketed silicone products. I just purchased 100 percent silicone and it was 12.99 a tube.
 
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