In the course of remodeling older homes, I’ve developed the window box/greenhouse shown in the drawing. Its deep recess gives the same comfortable feeling of a window in a thick stone or adobe wall, and makes space for plants and other things.
The heart of the design is a 2×12 frame built with clear, dry lumber and then nailed into the window opening. The frame is easily cut and assembled on the job site with portable electric tools and can be fitted with any combination of casement, awning or fixed sash (new or used). Inside, I trim the edges with casings consistent with other openings in the house. For weather protection I install a sloped metal flashing above the window and caulk along the jambs and sill. To date, all the windows I’ve built this way have proven to be weathertight.
Glen Jarvis, Berkeley, CA