[jte1130]

Not really sure what topic this would fit under so I threw it in the general category. I had replaced my thru the wall a/c last summer and never got to sealing up the outside since its on the 2nd floor and I needed a large extension ladder.
Finally got my hands on a ladder now I have a question. I was going to caulk it between the sleeve and the siding. However this sleeve is slightly smaller then the original. I had put in some 1x4's to build up the opening a bit. When I seal it from the outside can I caulk directly on top of the wood to seal the gap between the a/c sleeve and the siding? Or should I apply something else first?

 

[Ron6519]

If the gap is 1/4" or less, you can just caulk it. If it's larger, say 1/4"-3/8"use a backer rod to take up the space and caulk the backer rod. More then that would require something else. It would depend what it looks like.
If you did it correctly, the gap shouldn't be more then 1/4"
Backer rod is sold in the big box stores in the weather stripping aisle.
Ron

 

[jte1130]

There actually is no gap between the a/c and the built up box. What I'm worried about is on the outside of the house the 1x4 that I used to build up the box is now slightly exposed. Since the siding and flashing mathched the original hole there is now a slight exposure of the wood. I just was wondering if I could caulk over the wood.