Seal around windows, doors, and lights

I was at a reputable dealer yesterday to get caulk (not camping world). They only had dicor and 100% silicone caulk. I asked them what to use, use dicor for the roof and silicone for windows and doors and everything else. I told him I had read to never use silicone, he disagreed and said they put silicone on all trailers they sell or service. This is a reputable dealer (in OR) that sells a NW brand many rave about. I was very surprised, but purchased the dicor based on this website. Glad I read through these treads. I'm replacing my downspouts and silicone is not the right product...

My experience:

OSI QUAD is used around doors and windows on houses and buildings. It is available in colors, but typically only carried in white, black, grey & beige at Home Depot & Lowes. Works good on aluminum sided RV's. Should work good on other RV siding, but can't positively say it does. Also used it to seal around new PVC brick molding around doors and windows on a house and the doors and trim on my new wooden shed.

From the mfg:
OSI QUAD is composed of elastomeric polymers and high quality synthetic resins. This product offers the superior adhesion characteristics and unmatched elasticity found in high performance sealants. It yields a tough, rubbery seal which resists outdoor weather-related elements.

With resistance to UV and extreme temperatures (20°F to 120°F) and proven wet surface application, OSI QUAD is the versatile and durable choice for professional contractors.

mosseater wrote:
Dicor or equivalent only. Once you put silicone in place, nothing else is ever going to stick to it.

Thanks, that is the reason. (Getting brain full syndrome)

mosseater wrote:
Once you put silicone in place, nothing else is ever going to stick to it.

Not even more silicone.

If it's something I want to last, I go with polyurethane caulk.

Because it doesn't work and will fail.

For whatever reason, silicone caulking randomly will not get good adhesion to both surfaces and no way to predict exactly where it doesn't get good adhesion, creating random weak spots. Those random weak spots over time fail just enough to allow water to wick it's way right past the silicone.

Additionally, cured silicone is a real bear to remove and once cured not even new uncured silicone will adhere to the old cured silicone, ever, making your next repair a real time consuming nightmare to correct.

Silicone caulking is pretty much worthless.

Lets just stick with what does work, remove the window/door frames, remove the old butyl rubber caulking (removes easily with mineral spirits) and refresh with new butyl rubber caulking (rope or flat).

Yes, butyl caulking does dry out over time.

Yes, butyl caulking does crack over time.

Yes, butyl caulking will need replaced periodically.

But, even with those issues it simply works and will do so for 5-6 yrs at a time and unlike silicones it is easily replaced and if you compared the cost of butyl caulk vs a bunch of tubes of silicone it is very low cost.

And don't be tempted to take the lazy way out and slather on any caulking on the outside of the frames or trim, it just wastes money, time and looks horrible and will leak even faster.

Dicor or equivalent only. Once you put silicone in place, nothing else is ever going to stick to it.

Your reading was accurate IMO and silicone is not recommended by most RVers.