I went to replace all of the pipe for a pellet stove insert and discovered that the installer did a poor job of following any of the manufacturer’s guidelines for rise on the pipe or the appropriate thimble usage. I now have a 14” x 14” hole that accommodated a gas stove thimble and is lower than necessary.

I need to raise the opening ~4” and reduce the size to a 7x7 roughed in opening for the appropriate thimble.

I was going to pull some siding from above to place on the lower portion of the wall and raise the rest of the siding up incrementally, and retain the outside appearance of the same size opening (yet framed in smaller behind with a sheet of aluminum with a cutout for the thimble, but the sheets don’t line up to accommodate that.

The roughed in framing and moving the opening up isn’t an issue for me. Trying to determine how to finish the outside without looking dumb and provide a water/airtight finish.

No availability for the type of siding that was used (no extra and no longer made).

Any ideas?



Close up

Siding Planned Opening

  • It's not really clear what you're asking. Gray double-4" (or 5") vinyl is available almost anywhere siding is sold, though it may not match color exactly due to aging. You'll need either more siding or more J-channel (to extend the opening). Are you saying that neither are available?
    – isherwood
    Oct 19, 2020 at 19:10
  • i agree with @isherwood ... you described the project, but you did not ask a question ... any ideas? is a nonsense question if you don't say what you want to know .... if it's about the siding, you could try to move the siding strips
    – jsotola
    Oct 20, 2020 at 0:20
  • 1
    @isherwood More j channel is the obvious answer that I was just overlooking. I was way over complicating this getting stuck in the idea of getting replacement siding to make the opening smaller and not having matching siding available. I'll replace j-channel to move the frame up and more than likely just put a sheet of aluminum behind the wall and in front of the thimble to fill up the space.
    – Russ W.
    Oct 20, 2020 at 20:08
  • @jstola Sorry. A case of the I know what I wanted to know in my head and didn't articulate it well. I was indeed looking for a solution on how to fill the space with a smaller thimble without replacing or adding more siding. Looking for how to best make the larger hole in the siding look decent without adding more siding.
    – Russ W.
    Oct 20, 2020 at 20:10

1 Answer 1


I would get some J-channel from your nearest siding store. It's almost universally available. Cut the opening a bit taller, fit new top and side channel, and flash around whatever surface treatment you like.

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