Fastening and Finishing PVC Trim

Josh Buesking, owner of Louisville Exteriors, in Crestwood, Ky., says that he often leaves the PVC trim he installs unfinished and has had no complaints.

Concealed fastener systems use self-countersinking screws and special bits that drive the screws to a specific depth.

The hole in the PVC that was cut by a countersunk screw is concealed with a small cylindrical plug of the trim material that slides into the hole and is tapped flush to the board surface with a hammer.

When using a concealed fastener system, drive the screws perpendicular to the surface of the trim.

Some contractors prefer to use nails to fasten PVC trim. One trim manufacturer recommends using the same nails—either stainless or galvanized—that you use to fasten wood trim or siding. These can be driven by hand.

Azek specifies that if you are using pneumatic tools to attach PVC trim, fasteners should have a full round head (instead of clipped-head or finish nails). Set the pressure so that the nails are set just below the surface of the board.

Wire collation doesn’t always break off cleanly and any remaining pieces of wire can rust and discolor the trim.

Nail heads will be visible, so maintain a neat pattern.

An unglued scarf joint allows the board to expand and contract without visually opening up.

On southern exposures, installing a wood subfascia or blocks between the rafter tails helps to stabilize the fascia.

This house with unfinished PVC trim was built more than 10 years ago.

This unfinished PVC trim was installed more than 10 years ago and still looks great, except for some discoloration around the cut edges.

When PVC trim is ripped, open interior cells are exposed, allowing moisture to penetrate and mold and mildew to develop.

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