How to Install PVC Trim
See the unique methods that are needed to install this trimwork material
Synopsis: Although PVC trim can look like wood, it doesn’t behave like wood, so it requires some unique installation methods. For example, PVC expands as it gets warm, so long runs require a gap at butt ends. Use a scarf joint to join PVC trim boards; use PVC cement for any joint that does not require an expansion gap. Find out more in this video.
Video Transcript: Although PVC trim can look like wood, it doesn’t behave like wood, and requires some unique installation methods. PVC expands as it gets warm, so long runs require a gap at butt ends.
Clear the product shown here requires a 1/8th inch gap per 18 feet when installed at 70 degrees. In hot weather, make the gap a little smaller. In cold weather, make it a little larger. Fill gaps using manufacturer recommended sealant. Just like with wood use a scarf joint to join PVC trim boards.
A scarf is made from two opposing miters that are glued together with manufacturer recommended cement. PVC cement is used on any joint that doesn’t require an expansion gap.
For fastening use stainless steel trim nails so the nails will last as long as the trim. Nail within two inches from the edge of the boards and at least every 18 inches along the length.
You can also use a screw and plug system. This one from Fasten Master has plugs made to match clear products.
For exposed edges sand smooth with 150 or 220 grit sandpaper
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We install pvc trim a lot and I would say use the fastenmaster screws instead of nails. It allows for adjustment after install and it will stay put during expansion and contraction. I second the glue on mitered joints, we had to take one apart and it will rip the guts out of the board before the glue leaves loose.
PVC seems like a cool material, but it has serious health concerns:
1) It is very environmentally hazardous on the manufacturing end for the workers and for the communities surrounding the PVC plants.
2) It is highly toxic when it combusts, because it releases massive amounts of sulphuric acid vapors, which is why many State Fire Marshals have co-authored a position letter to this effect, which was sent to developers and architects so as to discourage its inclusion in projects.
Yes, this bums me out because it is so easy to work with and to achieve great results with all at a cheap cost, but this is one of those cases where something almost seems too good to be true and probably isn't.