Installing Trim Around A Plastered Window Well
Simple Window Trim Dresses Up Window Opening:
Recently I was asked what I could do to dress up a basement recessed window that had no trim and wa
s all plaster walls by installing trim around a plastered window well.
The designer on the project wanted the window to look like the windows upstairs, which had window trim and a traditional window sill. This was an easy fix I so I suggested we add a half round molding to the plaster opening bottom to simulate a window sill and then install colonial casing [similar trim to what is on the interior doors in that room] around the window opening.
It’s All in the Reveal
The first step was to mark my reveals around the opening. I use 3/16″ as my reveal. Once that was done I measured the width of the two side reveal marks, added the width of my trim multiplied times two and then added for sill nosing over hang of 3/4″ on both sides.
[ FORMULA: width between reveal marks + 2x Trim width + 1.5″ for sill overhang] I then used a router to rout a half round on three sides of a 4″ board, then ripped the board down to 1-1/4″ wide.
Start With the Sill Trim
I applied this nosing to the wall below the window opening with adhesive caulk and finish nails. 
Next I applied trim to the two sides of the opening and then ripped the top trim on the table saw to fit tight to the crown molding. I finished this project by adding trim under the sill nosing to form the stool trim. forty-five degree bevel returns to the walls finish off the trim nicely.
