Adapting RV Windows for 2-1/8 Inch Thick Walls

TheHoboHouse

Member
Joined
Jan 26, 2026
Posts
11
Location
Colorado
Most windows seem to be for up to 1-1/2" thick walls. However, my walls are 2-1/8" thick (= 1/2" ext. ply + 1-1/2" framing/insulation + 1/8" interior ply).

There are a few 2-1/8"+ window sellers there, but they are considerably more costly with less options.

I did look for posts about adapting th 1-1/2" windows to thicker walls, but didn't find a clear description of the solution that I was able to fully follow.

I'll have the opening framed by 2x2s (1.5" actual), so the window will attach to it from the outside, but then what about the gap between the inward-facing metal window frame lip protruding in through the hole and the interior trim ring? Is it a matter of somehow DIY bridging that gap? (I'd like to avoid recessing the window/trim ring into the interior wall.)

Anyone have any pointers or pictures of what they did? (Or a thicker window seller at a comparable ballpark price as the 1-1/2s)?
 
Quick update... Since I didn't get any replies or find any great solutions I liked, I ended up paying a bit more for the 2-1/8" window from Vintage. Did a dry fit and it looks like it will just recess a bit in from the interior wall (trim ring is somewhat of a window sill with a recessed rim with flange, with the window attaching to it for clamping).

I looked for just a stand-alone "deeper wall" trim ring like this, so I could use it with any standard-depth window, but no luck finding one with right dimensions / curve radius. I could have fashioned a custom flange, but it was not worth the minimal cost savings or water ingress risk.
 
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