Expansion and Contraction
PVC trim expands and contracts with changes in temperature. Properly
fastening and
bonding the trim along its entire length will minimize expansion and contraction.
- Use stainless steel nails or screws designed for wood trim and long enough to penetrate the substrate a minimum of 1". Screws are better for limiting the thermal movement of the trim.
- Allow the trimboard to acclimate to outside temperatures before installing.
- Allow 3/16” space per 18’ run of the trimboard for expansion and contraction. Use a UV resistant acrylic based, polymer based, or polyurethane caulk to fill any gaps between boards for appearance. NPC’s solar seal 900 in trimboard white is recommended with the trim.
- Bond joints between pieces of pvc trim to eliminate separation. Be sure to allow adequate expansion and contraction space at the ends of these long runs.
- Product that cannot be face nailed in accordance with our recommended "on center" spacing will require more room to accommodate expansion.
- Product facing direct sunlight may be susceptible to a larger temperature range.
- You can further restrict product expansion and contraction by decreasing the "on center" spacing between fasteners to 12” or less and bonding boards to substrate when feasible to do so.
- When utilizing a bevel or shiplap joint, leave a full 3/16” gap when installing on a day where temperatures range from 35°F to 45°F.
- When utilizing a bevel or shiplap joint, leave a gap just large enough to accept a bead of sealant when installing on a day when temperatures range from 80°F to 100°F.
- Scarf cut joints are preferred over butt joints.