Originally Posted by Scubawise
can I used a 15 or 30 year regular white from lowes home depot or need something special?
I wouldn’t. The specialized recommended product is “self-leveling lap sealant”. Often called “Dicor” - which is a common brand. As the name suggests it flows to some degree on horizontal surfaces (like roofs). It is relatively cheap and readily available and given what you probably paid for your RV why take chances? They also make lap sealant for vertical surfaces like windows and corner seams. I do use urethane caulk on the sides but not silicone. It simply isn’t a first line product anymore. At least not for joints that flex a lot like RVs do.
Also plan to inspect and reseal your roof and sidewalls where needed every 3 or 4 months. No aspect of RV ownership is more important than keeping water out!