Installing Window Boxes

DEAR TIM: Is there special type of installation required when installing a window box or garden box? Is flashing required to be installed over the limestone sill? Is other flashing required around other parts of the window? Thanks, Dan N., Deerfield, Illinois.

DEAR DAN: The installation of window boxes is a function of their design. Some window boxes are made to rest on platforms while others have a special lip that allows the window box to hang from special stainless-steel clips. I prefer the fiberglass window boxes that use this special clip system.

You do not need flashing if you keep the window box away from the side of the house ever so slightly. Water problems happen when you install a window box against the side of a house so no air can get between the box and the side wall of the house.