What is a Jamb Liner?
Definition of Jamb Liner in Construction Smaller pieces of wood or vinyl, in comparison to the typical, full size, jamb extensions. These jamb liners provide custom size depth of window and door frames, to accommodate varying thicknesses of exterior wall construction. The need for jamb extensions as well as jamb liners has become increasing more common, due to the amount of insulation being required and installed within exterior walls. The ability to use a small and simple jamb liners is not the issue that the use of larger and more invasive jamb extensions are. Normally the jamb liner is installed in the field and is not installed at the factory prior to shipping to the project site.