Pecora 895 NST has been specifically designed for:
• Structural glazing of glass, metal and plastic. It may also be used as a weatherseal in structural glazing applications.
• Non-structural glazing applications including cap, toe and heel beads and as a weatherseal in glass to glass butt joint glazing.
• Sealing expansion and control joints in precast concrete panels, metal curtain walls, and natural stone.
• Perimeter sealing of doors, windows and other building components.
• Adhering stiffeners to building panels.
• Use in unitized curtain wall systems.
• Security glazing and impact-resistant window systems
Questions about Pecora 895? Contact Us.
Weatherseal Joint Designs:
Proper sealant dimensions are critical when installing elastomeric joint sealants. Generally, a sealant width-to-depth ratio of 2:1 is recommended. Dynamic joint conditions will require a minimum 1/4” width and 3/16” depth in order to maintain the sealant’s movement capabilities. For joints greater than 1”, consult Technical Services. Open-cell polyurethane foam or closed-cell polyethylene are the recommended back up materials for most joints*; use polyethylene tape for joints too shallow to allow backer rod. See Figure 2. These materials permit application of a thin bead and act as bond breakers, which allow the silicone sealant to stretch freely with the joint. *Use a size that will compress 25% when inserted into the joint. When using closed cell polyethylene foam, extra care must be taken not to puncture the rod which can cause outgassing and bubbling/blistering in the sealant. The width of building expansion joints varies because of seasonal and daily changes in temperature. If Pecora 895NST silicone building sealant cannot be installed when the design width is approximately halfway between the dimensional extremes, the design joint must be at least twice the total anticipated joint movement. Good architectural practice calls for joint design of four times the anticipated movement due to construction tolerances and material variations. Glazing rabbets and joints should be designed to allow installation and retention of the bond-breaking, back-up material during the installation and curing of Pecora 895NST silicone building sealant. Lap shear joints should have a bead width which is equal to or greater than the total anticipated movement. See Figure 3. Small curtainwall panels and lites should allow a minimum width of 1/8” (3.2 mm) for the sealant bead. Larger panels and lites which expect a great deal of movement, should allow a minimum width of 3/16” to 1/4” for the sealant bead. Glazing of plastic lites and sealing of wall panels fabricated of plastics require larger than usual joint dimensions due to the greater movement potential caused by plastic’s higher coefficients of thermal expansion.