Cap beads seal the exterior line between glass and frame, often over glazing tape or a gasket. They take direct sun and weather, so silicone is standard. A cap bead must bond to clean glass and metal and be tooled to shed water. Covering the frame weeps with a cap bead, a frequent mistake, traps water in the pocket.
Run the cap bead in black silicone and keep it off the weep slots in the bottom rail.
Also heard as
- cap seal
- capping bead
Related terms
Heel bead
A sealant bead at the inside edge of the glass where it meets the frame, forming a continuous air and water seal.
Wet glazing
Sealing glass into its frame with gun-applied sealant instead of preformed rubber gaskets.
Weep
An opening at the base of a wall or window system that lets collected water drain out.
Silicone
A sealant with a silicon-oxygen backbone, prized for UV resistance and high movement capability.