Window and door trim

Windows and doors must be installed so that they are sealed to the air barrier and must be flashed and sealed to keep water out (see Figure 130 and Figure 138). Exterior trim is used to conceal gaps around windows and doors and cover the exposed ends of the siding. The trim can be wood or prefinished metal, which is the most commonly used.

Figure 138

Section through doorframe at sill

Section through doorframe at sill

Source : Canada Mortgage and Housing Corporation (CMHC)


Exterior trim and millwork that needs to be periodically coated with paint, stain or clear finishes is becoming increasingly less popular. Exterior, site-coated surfaces can be expected to require maintenance at least every three years. Exterior trim and millwork is often difficult to access without ladders or other special equipment, further increasing the cost of maintenance.

Factory-finished metal and other trim materials are recommended because their appearance can be maintained for a long period of time by cleaning rather than recoating.

Resource Conservation

Exterior trim and millwork that uses finger-jointed wood, or medium/high density fibre, board conserves forest products.