High-density polyurethane is a popular choice for decorative trim, thanks to the wide variety of shapes and profiles and the material’s long-term durability. Some manufacturers of urethane products offer thousands of pieces of both interior and exterior trim, including crown molding, entrance trim, window trim, shutters, medallions, and other decorative millwork. Because the trim products are manufactured using a mold, rather than milled from solid wood, the profiles can feature artistic patterns and embellishments with the classical appearance of carved wood. To achieve the same intricate cornice moldings with wood trim that are available in urethane, one would have to install multiple sticks of smaller molding with varying profiles, building up to the overall final shape piece by piece.
The urethane material weighs less than wood but can be nailed, cut and sanded just like wood. The joints should be fastened with a polyurethane-compatible adhesive. For outdoor use, urethane trim doesn’t have the maintenance problems of wood. It resists insects, cracking, peeling, chipping, swelling, splitting and rotting. Polyurethane molding products are available as double-primed with an exterior grade coating or as finish-painted from the factory.
Randy Stephenson, a professional remodeler in central Alabama, recently shared a tip for hanging classic-style urethane molding that minimizes the use of mechanical fasteners and the associated repair work.
Stephenson’s project involved a double course of prefinished classic-style crown molding to decorate the look of a vaulted ceiling.
First step is to set up a stable work surface that supports the lengths of molding to be joined.
Moldings that feature a continuous pattern should be carefully cut so the mating pieces will marry seamlessly to continue the pattern without a visual break in the artwork.
Stephenson’s solution to join the connecting pieces required a clear two-part epoxy applied to the two mating surfaces.
To make sure he didn’t adhere the molding to the work table, Stephenson made a jig to support the joints that provided an air space a few inches wide beneath the joint.
To reinforce the epoxy-joined joints, Stephenson used contact cement to glue a 1/2-in. plywood block to the back of each connection, bridging the seam.
To keep the plywood blocks in a uniform position so they wouldn't shift around while the glue dries, Stephenson measured and marked their positions on the trim and fastened them to the rear of the joints with screws short enough to avoid penetrating the decorative face of the molding.
After the glued joints had completely dried, Stephenson cut the strips of molding to final length then transferred the measurements of the plywood blocks to the wall where the trim would be installed. After marking the block locations, Stephenson made drywall cutouts that would nest the plywood blocks and allow the molding to install flush against the wall along the ceiling.
To assist with installation, Stephenson fastened a temporary ledger board along the wall, which was positioned to support the molding and align it with the ceiling.
To reduce the need for nailing, Stephenson fastened the molding in place with urethane-compatible construction adhesive and held it in place with a few strategically placed pin nails while the glue dried.
The end result was a professional-grade project that preserved the factory finish of the crown molding without the need for repairs after installation.