Dave Solberg is a leading expert in the RV industry and author of the “RV Handbook” as well as the Managing Editor of the RV Repair Club. Today he discusses sealing around RV windows.
Dear Dave,
Thanks for the great, informative answers you give to readers’ questions. I’m wondering if you would advise sealing around windows before looking for a leak. If so, what type of sealer do you recommend? If not recommended, why not? Thanks. —Louie
Dear Louie,
Thanks for reading and submitting a question. If I were you, before I started sealing around windows I would investigate the leak further. Typically you do not need to seal around a window unless the butyl tape has started to crack or separate. Keep in mind, water leaks can show up in one area but the leak actually started in a totally different spot.
RV window installation
Most RV windows are installed with a “sandwich” design, meaning the outside frame with the glass has a lip that fits against the sidewall with a putty-type butyl tape used for sealant. Some manufacturers use a rubber gasket and silicone designed for fiberglass. The inside frame is screwed to the outside frame and sandwiches or pinches both frames against the sidewall. If the butyl tape or silicone is applied properly, you do not need any additional silicone. However, I have seen some manufacturers put a cap seal bead of silicone on the top.
So start by finding where it is leaking inside the unit and look for possible infiltration spots such as sealant areas on the roof. Look at all the sealant for cracks or gaps such as the roof-to-sidewall joint, around any vent and skylights, or the front cap. Water can get into these areas and travel along the hollow framework and come down the wall. So just sealing the window might not help if it’s not the entry point.
Proper sealant
As for the proper sealant, it depends on the material it will be applied to. If it’s a rubber roof, you will want to use a sealant designed for rubber. Fiberglass is generally a 311 sealant as it is a little more smooth of a surface and it will adhere better.
If you find an area that looks like it is cracked or pulling apart, you can use a small amount if the area is small, otherwise I would recommend removing as much of the bad sealant as possible and reapplying. Another option would be to use Eternabond, which is a “go to” for many RVers.
Read more from Dave here.
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So, back to leaks at windows, Dave, certainly one is not going to use Eterna Bond. Suggestions? Replace butyl? Apply silicone around window?
Recently, I had a leak that dripped across the dashboard. I chased it for about a year. It was hard to find since it only leaked in driving rain.
Then the front windshield cracked. There was rust where the windshield sealed against the metal! That was the source of the leak. The people who replaced the glass ground the rusted area then primed the metal. They’d obviously seen the problem before.
A few years later the other side leaked! Once again, it seemed to only happen in driving rains. I first suspected the window, but fortunately, that was not the problem; the leak was above the windshield. The RV was old enough (2003) that the caulk in the accent lights across the top-front of the RV had dried out. Once they were all re-caulked the leaks stopped.
Some windows do leak if a blowing storm. Ours did. Water was running down the window. Sealed them and no leaks.