Do not use silicone caulk!
Silicone sealant is great indoors for caulking cabinets, but it does not work on RV exterior surfaces for two reasons. First one: RV Roofs made of rubber either EPDM or EPO will not allow adhesion of silicone. Secondly, if you do use silicone in areas of aluminum trim and fiberglass joins, it will work and seal these surfaces successfully, but when you want to renew the caulk, you cannot apply new silicone without totally removing the old silicone caulk. Silicone caulk does not adhere to cured silicone.
The following two images show a 2018 Heartland RV with silicone used to seal the rubber roof edge moulding. Notice how the reaction with the rubber compound has already cracked and fragmented the silicone only after two years! At least the old caulk was easy to remove.
Always use caulk compatible with rubber RV roofing materials.
Incorrectly installed in the factory! On the right side of the black aluminum trim, the silicone caulk is fully degraded and flaking off the RV’s rubber EPDM roofing membrane. The left side of the trim, where the aluminum is sealed with the fiberglass, the silicone is still fully intact.
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