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Ask Dave: Can I seal my RV’s windows without taking them out?

Dear Dave,
Is there a way to seal around the RV’s windows without removing them? Is there a sealant that can be used around the outside of the window that is safe to use with the various exterior wall materials? —James, Coleman 2515RL 2020

Dear James,
There are a variety of different window manufacturers such as Hurd, Hehr, and now Lippert, and there are also different installation designs. The traditional RV window has the glass in a metal frame with a flange that is installed from the outside with butyl tape between the flange and the sidewall. This is a putty style material that typically is the only sealant needed.

The window and frame are sandwiched to the sidewall with a metal frame secured from the inside. Some manufacturers also add what we call a cap seal, which is a silicone bead added to the top part of the window trim. From what I see in the brochure and videos online, this is the type used on your Coleman.

What to do if the RV window is leaking

If you are experiencing a leak at your window, I would recommend cleaning the entire area with denatured alcohol and inspect the butyl tape. Sometimes the tape gets pinched out as the sandwich design of the window moves and gets tighter. You can trim some of that excess putty away and use a non-sag sealant designed for fiberglass such as the Dicor brand. Run a small bead around the frame and smooth it out with your finger. An old tip from my grandfather: A little spit on your finger helps to keep the silicone from sticking!

One other thing you will want to do is check the screws inside to make sure they are tight. Road vibration can make them loosen over time and create a leak as well.

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.

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billh42
2 months ago

Use dish soap and water in cup to wet your finger before smoothing the sealer. Better than spit. Also masking tape will give you a sharper line so it looks “factory fresh”.

Bob
2 months ago

Using the term ‘silicone’ is misleading. True silicone, RTV, sealant that you find in most big box stores should be avoided. It is extremely hard to remove if needed. Also, once cured it will not allow you to reseal the area. RTV silicone, or any other sealant will not stick to it once cured. Ones like Geocell and Lexel be cleaned and reapplied.

Greg S
2 months ago

My Winnebago Class A has the butyl seal with no silicone cap seal.
My HitchHiker fifth wheels had silicone all the way around the window frames, but no butyl seal between frame and fiberglass.
What you think may be a leak could be condensation inside with no place to go because the small weep holes at the bottom of the frame are clogged.
It is also easy to get water inside if you hit those weep holes with too much water from a hose while washing your rig.
Finally, if the seals are good and you still have a leak, it is possibly a bad seal between the fram and the glass.

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