Q. Installing Interior PVC Trim

On a bathroom remodel, my client has requested flat 1x6 PVC trim fitted with a profiled PVC cap piece to match the look of the period baseboards in the rest of the house. What’s the best way to smooth out the routed surfaces after I cut the profile in the cap piece? And should the joints be glued, or should I leave them unglued so they can expand and contract (the technique I use for exterior PVC trim)?

A.Gary Katz, a frequent contributor to JLC and moderator of the JLC Online finish-carpentry forum, responds: I’ve installed PVC trim on a number of interior projects using the same basic techniques I use with wood and have never had a problem. I’ve had the best results with Versatex cellular PVC (versatex.com). It has sharp, clean corners and nice edges, mills beautifully with a router bit, and has a finish that accepts paint very well; it’s not mirror-glossy like some other brands, which practically require etching to bond well with paint. To smooth routed PVC edges or surfaces that have dried PVC glue on them, I use fine-grit (P320 or P400) sandpaper, which allows me to buff a profiled PVC edge right back to its almost-shiny factory finish.

I miter outside corners and cope inside corners, fastening the outside corners together with glue and one-inch-long 23-gauge pins, the same fasteners I use for wood. To fasten the trim to the wall, I use 2 1/4-inch-long 15-gauge nails. On the interior of a home, nail holes in PVC can be filled with almost anything used with wood; Bond-and-Fill (bondfill.com) is a safe choice. To glue joints together, use PVC cement, since wood glues like Titebond II don’t work all that well with PVC. Sometimes I use Versatex’s branded PVC cement, but I’ve also used 2P-10 (fastcap.com), especially on self-returns and small pieces. If you use 2P-10, be careful — and don’t use the activator: It will melt the PVC and bond your fingers to the plastic instantly. I don’t bother using any adhesive on cope joints, whether I’m working with wood or PVC trim — there’s nothing to glue to and no reason for it.

One reason I don’t worry much about the PVC expanding or contracting is that interior trim runs are usually much shorter than exterior trim runs, where the potential for movement is much greater. Also, PVC trim shrinks and expands because of changes in temperature; if it’s installed when the temperature is anywhere near 70°F, it’s unlikely to move much later on.