Pecora 895 NST is designed specifically for:
- Structural glazing of metal, plastic and glass. It can also be used in structural glazing applications as a weatherseal.
- Non-structural glazing applications including toe, heel and cap beads and as a weatherseal in glass to glass butt joint glazing.
- Use in unitized curtain wall systems.
- Perimeter sealing of windows, doors, and other building components.
- Sealing expansion and control joints in natural stone, metal curtain walls and precast concrete panels.
- Adhering stiffeners to building panels.
- Security glazing and impact-resistant window systems
Questions about Pecora 895? Contact Us.
Weatherseal Joint Designs:
When installing elastomeric joint sealants, proper sealant dimensions are critical. In general, a width-to-depth sealant ratio of 2:1 is recommended. A minimum 1/4” width and 3/16” depth is required for dynamic joint conditions to maintain movement capabilities of the sealant. Consult Technical Services for joints greater than 1”. Closed-cell polyethylene or open-cell polyurethane foam are the suggested back up materials for most joints*; in cases where joints are too shallow to allow backer rod, polyethylene tape is used. See Figure 2. These materials act as a bond breaker and permit application of a thin bead which allows free stretching of the silicone sealant 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 blistering/bubbling and outgassing in the sealant. Width of building expansion joints varies because of daily and seasonal temperature changes. The design joint must be at least twice the total anticipated joint movement when Pecora 895NST silicone building sealant cannot be installed and the design width is around halfway between the dimensional extremes. Due to construction tolerances and material variations, allow joint design of four times the anticipated movement according to good architectural practice calls. Glazing joints and rabbets 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. A minimum width of 1/8” (3.2 mm) should be allowed for small curtain wall lites and panels for the sealant bead. A width of at least 3/16” to 1/4” for the sealant bead should be allowed for lites and larger panels which will require a great amount of movement. A bigger than usual joint dimensions is required for securing of wall panels fabricated of plastics and glazing of plastic lites due to possible greater movement caused by plastic’s higher coefficients of thermal expansion.