I had to remove some tile as per our window contractors request. Windows went in well but I need to finish up these window sills again.

I’m pretty sure I just need to buy some primed pine trim and simply cut it down to size. Sound right?

So do I just cut it down to size and nail or glue it into the frame? Should I bother removing the previous massive adhesive chunks or just compensate in my measurements?

Also, any tips on whether the depth of the lumber (like an inch) can go above the already existing trim or should I do all I can to get it flush?

Thanks 😊

enter image description here

  • 1
    This depends on some dimensions that are in play here, your skills at trim carpentry and if you need to keep the picture frame trim that is already there. Also are all the windows needing to be done, or just this one? The process can be easy or rather detailed, depending on what you want.
    – RMDman
    Mar 21 at 1:13
  • Might help if you let us know how far the casing extends past the current surface, and how side the sill is. I'm assuming you don't want to simply re-tile? For me, I would get some wood (or possibly PVC board), cut to fit, and paint. You could also use drywall. (Wood and drywall may also provide some warning if/when the window starts to leak.)
    – Huesmann
    Mar 21 at 13:17
  • You likely will not find a board the perfect width. Do you have the ability to cut a board lengthwise (rip), like do you have a tablesaw, or other saw with a fence? Mar 21 at 13:52
  • Your questions are somewhat subjective. Why aren't you reinstalling tile?
    – isherwood
    Mar 21 at 14:06

1 Answer 1


If I was doing this job I'd be removing the casing, installing extension jambs, and refitting the casing to them. The casing gets shorter in that scenario, so you can reuse it. This is the way to a professional, original-look installation.

  1. Procure some jamb material. This can be many things, but needs to be as deep as the dimension from the window face to the drywall face, and it should have at least one finished edge. They should be at least 3/4" thick. Paintable wood or vinyl are common choices.

  2. Carefully remove the casing. Be especially careful to not pry on the miters and unduly damage them. Pull nails through the back side and set them aside.

  3. Install the jambs as a box with lapped corners. Convention and best practice has the head and sill overlapping the sides. You can build them in advance or install by piece. Shim them off the old tile surface so you have a uniform, parallel, suitably sized reveal on the window. I'd go with a small overlap inside the channel in the window in order to conceal it.

  4. Decide whether you want insulation. Even if you don't need it for energy efficiency, it can really solidify the jambs. If so, low-expansion spray foam is ideal. Fill a bit at a time so you don't have a mess. It'll grow for 5-10 minutes. Trim off any excess with a knife.

  5. Refit the casing, overlapping the new jambs but leaving a reveal at the inside. Glue all miter joints.

The outcome will look something like this:

enter image description here


  • 1
    To point #1: don’t use mdf or particle board, as these respond poorly to moisture. Mar 21 at 21:32

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