Jambs & Thresholds For Fat Walls

JANUARY JLC 1998 ost windows and doors are manufactured to fit the 41/2-inch-thick walls that were the norm 20 years ago. Since the early '80s, when 2x6 exterior wall studs became commonplace, units designed to fit 61/2-inch-thick walls have also been made available. But the exterior walls of today's houses often include additional materials — a layer of rigid insulation, a double layer of 5/8-inch fire code drywall between the house and an attached garage, resilient channels to reduce sound transmission — that add another inch or more to the wall thickness. This isn't much of a problem with windows, because they can be mounted flush with the exterior sheathing, with extension jambs applied on the