Trimming out window interiors raises several design issues — as well as some practical concerns. Since I use only wood windows on my projects, I'll confine my comments to those. Many of the same problems arise with aluminum or vinyl windows, but their wider frames solve some problems and create others. There are three general ways to trim out the inside of a wood window: (1) Flat casings — the traditional approach (2) Plaster returns — a "trimless" system where the wall returns to the window frame (3) Window-box casings — an edge-on liner applied to the jambs, head, and sill of a window, projecting out from the drywall 1/2 inch or so The major design issues differ somewhat for each of these three trim
