Understanding Hurricane Product Approvals: Anchored vs Unanchored Storefront Window Jambs

Understanding the difference between anchored and unanchored storefront window jambs is critical for high-performance hurricane-rated glazing. The product approval anchoring detail pages outline all installation conditions under which a product has been tested—and in some cases, the frame profile itself may change depending on anchoring type.

For example, a steel-reinforced jamb used in an unanchored condition may be 3-1/4" wide, while the anchored version may only be 1-7/8" wide. That difference has major impacts on how finishes are detailed around the window system.

Another critical consideration is deflection. A 10'–12' tall unanchored jamb can deflect up to 1/2" under wind load. If the shim space and perimeter sealant joints are not designed to accommodate that movement, finishes can crack, fail, or leak. Proper planning must account for structural performance and the aesthetic and weatherproofing consequences.

Anchored vs Unanchored Storefront Window Jambs