What Is Window Trim Capping?
What Is Window Trim Capping?
Window capping (window cladding, window wrapping) in construction refers to the application of aluminum or vinyl sheeting cut and formed with a brake to fit over a building’s exterior wood trim. Screws, nails, or pneumatic fasteners may be used to hold the product in place.
The APA’s Architectural Performance Manual specifies that capping should be evaluated for its ability to withstand wind uplift pressures based on an appropriate engineering analysis (the material itself may have been rated as shear-rated but the unit installation was not); therefore, capping is typically specified as a panelized system rather than as individual pieces or panels.
A window capping unit is generally a two-piece assembly consisting of an upper and lower section, each fabricated from aluminum or vinyl. The sections are precisely cut and formed with a brake to fit around window openings, with either one or both ends being hinged to allow the sections to be swung open during cleaning or replacement of the glass.
If desired, the end pieces can be covered with wood trim so as not to stand out from the wall surface. The typical aluminum extrusion has a galvanized coating; anodizing can also be applied for appearance enhancement.
Metal sections are generally made from extruded aluminum stock and typically feature a minimum .015 metal thickness on all surfaces (including trim). A variety of other rigid and semi-rigid products (such as extruded PVC or PVC-coated stock) are available for both residential and commercial applications.
The APA’s specifications for window capping specify the use of an aluminum product but allow the use of other materials approved by the manufacturer.
In addition to aesthetic and performance considerations, window capping is usually specified to allow unobstructed wheelchair access. Requirements vary somewhat among manufacturers but commonly include highly visible signage indicating standard wheelchair access specifications.
