Hopefully this question is answerable. When making up window trim, there is typically a small reveal between the jamb and the casing. Is there a reason for having this, other than aesthetics / tradition?

Possible things that came to my mind, but I don't know if these are valid: easier to install, easier to hide imperfections.

I found this image that should clarify which pieces I'm talking about - jamb and trim/casing. enter image description here

  • When you say “jamb”, do you mean “frame of window” or “framing for window”? (I understand the casing to be the window trim.)
    – Lee Sam
    Commented Nov 23, 2020 at 19:49
  • @LeeSam I added an image to clarify. Casing == trim. Jamb == frame between the window and the inside edge of the wall. Commented Nov 23, 2020 at 19:53

1 Answer 1


Flush joints are both challenging to achieve perfectly, especially where several come together, and are generally ugly. A seam in a flat surface looks odd, as though something was added on due to poor planning.

It's that simple.

  • +1 for acknowledging the difficulty in aligning two pieces of wood perfectly. Look at the Craftsman Style. They just piled on layers of trim to make everything “appear” planned out.
    – Lee Sam
    Commented Nov 23, 2020 at 20:27

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