I currently go over my camper religiously looking for chances of leakage at least every six months. Seams on the roof, windows, etc. are checked for any signs of cracked sealant or separation. I treat them with Dicor in the two varieties, self leveling and goopy. This past trip it rained for three solid days and I was trapped inside a lot of the time. I began to ruminate over how well protected the unit was.When I was on the east coast I grew up using the 3M sealants for marine industry, notably 5200 and 4200 caulks that came in squeeze tubes and cartridges. These lasted for many years in salt water. They would also go through season after season of abuse from freezing and vibration. I can't believe there is anything that vibrates and moves more than a boat pounding the waves. Those sealants are tough, last for a long time and don't let go. I even used them to mount lighter weight things to fiberglass hulls with no screws with success.Why doesn't the RV industry use these? Is the Dicor superior because of flexibility? Lots of folks tell me to switch to Sikaflex products. I know people scream not to use silicone but I never hear why. Where is the holy grail of information on all things RV caulking?

I can only answer one of your questions. Once silicone caulk is applied, it works well for a long time. But it eventually needs scraped out and replaced. Unfortunately, even if you do a great job removing the silicone, and it looks spotless, there is still a film of silicone on the roofing/trim/whatever you scraped it from. Nothing will stick to that film, not even new silicone caulk.

Ranger Tim wrote: I know people scream not to use silicone but I never hear why. Where is the holy grail of information on all things RV caulking?Everything I've read on the forum about not using silicone is because nothing will stick to silicone, including other silicone. So, in theory, if you need to recoat a seam the new silicone will not stick to the old.Maybe that was true with the original silicone caulks? And maybe the newer silicone caulks don't have that problem? I don't know.I've had good luck with Dicor caulk but, I would consider using a different product if I knew there was not an adhesion problem.The RV Industry probably uses what works and is the cheapest.As for finding the Holy Grail on caulking, opinions are like other body parts, we all have one. I don't know if there is a one size fits all answer.

Silicone is just base material, when caulks have advanced formulas and silicone roof coating makes the best material it is. I tried all kind of caulks on my RV and marine caulks would turn yellowish within couple of seasons, not mentioning their adhesion to rubber roof was poor. Their internal strength played no role. The best caulk I experienced is the pictured below. It will stay flexible, is paintable and relatively easy to apply. Then what really made my rubber roof leak-proof was mentioned Henry's silicone roof coating, who will stick and feel gaps around all caulking.

I used 3-M UV 4000 marine sealant on compartment doors and horizontal seam on our Bigfoot. I believe Bigfoot and Northern Lite use this product at the factory.

Most of the recomended caulks are polyurethane basied, they dont get real hard like silicone and other caulks. This allows them to stay flexable. Silicon, is what they said above, not a great idea. You like the 3m , use it , its poly baised. I dont k ow what the quad is, but its miniral spiret clean up so probably the same. Polyurethane caulks you can clean up with miniral spirats and it becomes tacky again, so you can go over existing caulk if its adhered well. The others you cant. And always try to use the same stuff. Some may not play well with others.

3M 5200 Marine Sealant et al | Good Sam Community

16 Replies

stevenal
Nomad II
Jul 06, 2020
5200 is great stuff. I use it to seal screws and sink drains. Never tried using as a caulk.
Sjm9911
Explorer
Jul 06, 2020
Most of the recomended caulks are polyurethane basied, they dont get real hard like silicone and other caulks. This allows them to stay flexable. Silicon, is what they said above, not a great idea. You like the 3m , use it , its poly baised. I dont k ow what the quad is, but its miniral spiret clean up so probably the same. Polyurethane caulks you can clean up with miniral spirats and it becomes tacky again, so you can go over existing caulk if its adhered well. The others you cant. And always try to use the same stuff. Some may not play well with others.
bigfootgrey
Explorer
Jul 06, 2020
I used 3-M UV 4000 marine sealant on compartment doors and horizontal seam on our Bigfoot. I believe Bigfoot and Northern Lite use this product at the factory.
Kayteg1
Explorer II
Jul 06, 2020
Silicone is just base material, when caulks have advanced formulas and silicone roof coating makes the best material it is.
I tried all kind of caulks on my RV and marine caulks would turn yellowish within couple of seasons, not mentioning their adhesion to rubber roof was poor.
Their internal strength played no role.
The best caulk I experienced is the pictured below. It will stay flexible, is paintable and relatively easy to apply. Then what really made my rubber roof leak-proof was mentioned Henry's silicone roof coating, who will stick and feel gaps around all caulking.
gbopp
Explorer
Jul 06, 2020
Ranger Tim wrote:
I know people scream not to use silicone but I never hear why. Where is the holy grail of information on all things RV caulking?

Everything I've read on the forum about not using silicone is because nothing will stick to silicone, including other silicone. So, in theory, if you need to recoat a seam the new silicone will not stick to the old.

Maybe that was true with the original silicone caulks? And maybe the newer silicone caulks don't have that problem? I don't know.
I've had good luck with Dicor caulk but, I would consider using a different product if I knew there was not an adhesion problem.

The RV Industry probably uses what works and is the cheapest.

As for finding the Holy Grail on caulking, opinions are like other body parts, we all have one.
I don't know if there is a one size fits all answer.
srschang
Nomad
Jul 06, 2020
I can only answer one of your questions. Once silicone caulk is applied, it works well for a long time. But it eventually needs scraped out and replaced. Unfortunately, even if you do a great job removing the silicone, and it looks spotless, there is still a film of silicone on the roofing/trim/whatever you scraped it from. Nothing will stick to that film, not even new silicone caulk.

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3M 5200 Marine Sealant et al

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