07 Ultra Class C window leak

[lindana]

Overcab window has developed a leak. Outside wall under skin both sides of window is flexible (moves when pressure is applied) but inside wall is solid. Very little dampness on bed floor. I am being told I will need to replace whole front ($4500), but curious as to why inside is solid? Wouldn’t dry rot affect the inside wall?

[RCSMITH]

Side window or front window?

[lindana]

Front window. We are going to have to take it about 300 miles to be repaired by reputable guy.

[RCSMITH]

Front of upper bunk on our 2006 Ultra Super C is aluminum skin on outside which is fairly flexible. Inside wall is luan wood which does not give.

[lindana]

So, how bad is my damage do you think? Floor of bed is solid. Is it possible that we don’t have extensive dry rot?

[RCSMITH]

Unfortunately, hard to tell until you open it up.

[lindana]

Unfortunately, hard to tell until you open it up.
I’m feeling better about it. Pulled the bed cushions, no mildew. Rain coming in tomorrow and I will be able (hopefully), to see where there is seepage. Thank you so much for your input, Rich!

[RCSMITH]

Check where glass seals to window frame. Over time they can separate.

Good luck

[lindana]

Thanks so much, you’ve been a great help, Rich.

[jamesham]

We have had front window water leaks in our GS Yellowstone Ultra Class C. We have no front window because factory installed an entertainment center above the cab. But we have two windows in bunk area on either side of cab, and we have had to repair them.

We had a bubble in the fiberglass exterior but no damage to the inside paneling. Removed the window and dumped Gorilla Glue under fiberglass bubble and clamped for a week with lots of clamps. It worked. Reseated window using white 70% elastomeric caulk and it has held water tight for 3 years. Repeat on other side. Replaced the deck on the bunk area with new stronger piece of plywood because water leaks had caused a sag under the weight of the entertainment center. No mattress so no mildew problem.

Cost was just lots of caulk, glue, and clamps, plus 2 sheets of nice 3/4 inch plywood. There is a special glue sold online for 100 bucks especially to solve the fiberglass delamination problem but did not purchase.


Overcab window has developed a leak. Outside wall under skin both sides of window is flexible (moves when pressure is applied) but inside wall is solid. Very little dampness on bed floor. I am being told I will need to replace whole front ($4500), but curious as to why inside is solid? Wouldn’t dry rot affect the inside wall?

[lindana]

We have no delamination problem.
I’m thinking we may be ok. Rained for hours last night and bed flooring is dry! The caulking we did held. Going to try to get “2nd opinion!”
Thanks so much for weighing in. Owners always have good advice. ☺️

[jamesham]

In your first post, you said the exterior wall was flexible and moved in when pressed. That sure sounds like the start of a delamination problem. It is an easy glue fix when confined to a small area, but must be solved before a large separation happens and you have to remove large sections of exterior fiberglass. Delam usually starts below windows or edge corners when water seeps in and breaks the factory glue bond.

We caught ours in upper bunk while it was small and simple bottle of glue flooded into the void fixed the problem. Upper bunk area in Class C motorhomes frequently seem to have a problem.

Glad to hear you have no leaks. Best wishes that everything is OK.


We have no delamination problem.
I’m thinking we may be ok. Rained for hours last night and bed flooring is dry! The caulking we did held. Going to try to get “2nd opinion!”
Thanks so much for weighing in. Owners always have good advice. ☺️

[lindana]

The front panel of our unit is aluminum. I didn’t realize that fact until someone else with a similar unit mentioned it. I could see immediately the difference on the material compared to the sides. Thank you so much for taking the time to respond.

[jamesham]

Thanks for posting the new information. Yes aluminum cap vs fiberglass bonded wall makes a big difference. On our motorhome, the front cap is plastic and the rear cap is fiberglass not bonded to any interior wall panel. The plastic has had a few cracks and was a terrible choice by GS factory.

The front panel of our unit is aluminum. I didn’t realize that fact until someone else with a similar unit mentioned it. I could see immediately the difference on the material compared to the sides. Thank you so much for taking the time to respond.

[lindana]

We learn from each other!