PVC trim: Better than wood | Pro Construction Guide

PVC trim: Better than wood

For centuries, wood has been the material for exterior trim on residential houses and multi-family buildings. Fabricated from white pine, fir, cedar and redwood, it’s easy to cut, trim, rout, install and paint. But it also absorbs moisture, rots, requires painting and can be penetrated by insects. Fortunately, a number of engineered trim products are available: PVC trim and fiber cement are the most promising.

PVC trim

Cellular PVC can be molded into a wide range of trim shapes and dimensions. Examples include garage-door trim door frames, window and door trim, and decorative exterior molding.

PVC trim

Cellular PVC can be molded into a wide range of trim shapes and dimensions. Examples include garage-door trim (brick moulds, door jambs, utility trim); door frames; door and window trim (fluted casing, J-channel casing and sill nose); and decorative exterior molding (crown, quarter round and colonial casing). Cellular PVC trim is also available in different textures and several colors. (It is, however, paintable. Use a latex or oil-based paint and avoid dark colors such as black, crimson red and hunter green, which can cause thermal expansion.)

Cellular PVC trim won’t split or crack, doesn’t shrink or swell and resists termites and moisture (which causes mold and mildew). Toolbase.org estimates that labor costs for installing composite trim such as cellular PVC is 10 percent to 50 percent lower than for wood. The product also “cuts and machines very easily with standard woodworking tools,” says Noel King, design and development, Royal Mouldings, a Marion, Virginia-based cellular PVC product manufacturer.

Installation procedures vary by brand. Royal Mouldings, for example, recommends using 6d and 8d galvanized finishing nails for attaching its Never Rot cellular PVC trim products (and yes, it’s safe to use your pneumatic nailer). Nails should be placed 12 inches on center and ¾ inch from the edges. Pre-drilling is required if installation temperatures are at 40F or below.

Some brands call for “butt” joints to join sections together. “Never Rot” is like natural wood, however, and requires 45-degree miter cuts. Royal Mouldings also strongly recommends gluing all miter joints with a quality instant glue or PVC cement. This prevents gaps from occurring during thermal contraction.

Durable and cost effective

Like cellular PVC, fiber-cement trim offers several benefits over wood trim. It is resistant to rot, insects and hail damage; requires infrequent painting; and has minimal thermal expansion or contraction (which means dark paints don’t pose a problem).

Fiber-cement board can be used for fascias, corner boards, soffits and window and door trim. It doesn’t contain oil-based additives, which makes it a green product, says Chris Clark, trim business manager, James Hardie, a Mission Viejo, California-based fiber-cement product manufacturer.

Fiber-cement trim comes in several sizes and finishes. James Hardie offers its Harditrim MD (7/16-inch thick) and Harditrim XLD (1-inch thick) in 12- and 10-foot planks, respectively (both are available in 4-, 6-, 8-, and 12-inch widths). Harditrim MD comes in both “smooth” or “cedar-like” finish, while XLD is available in a smooth finish. Both products are offered primed or pre-painted.

Fiber-cement trim is more expensive on a per-foot linear basis than pine, spruce and fir, but less expensive than clear cedar. Its factory-applied primer or paint, however, give it an advantage in total installation cost, notes Clark. (If you choose to paint it, use 100 percent acrylic paints.)

Installation techniques vary by manufacturer and region. When installing Harditrim XLD, for example, use galvanized 2½-in. finish nails, says Bryan Walters, business development product manager, James Hardie. “If you’re building in coastal areas, I strongly recommend stainless nails.”

Nails should be 16 inches on center and kept ½ inch from edges. Walters also recommends using a pneumatic nailer, which allows you to slightly countersink the nail and “patch and paint over it.” Another tip is to use “weather cuts” (a 22½ -degree miter cut) to join vertical trim. This, he says, prevents water from accumulating in seam lines.

For your next project, consider engineered wood trim; it saves time and money during installation and gives your customers a less maintenance-intensive building solution. Clearly, it’s a win-win situation for both of you.

Prime cuts

For best results, opt for these blades. The goods news about cellular PVC and fiber-cement trim is that you can use many of same the tools (pneumatic nailers, miter saws) and techniques that you use with wood. However, for best results, consider these suggestions.

For best results, Royal Mouldings says to use a carbon-tipped blade lubricated with “spray furniture polish” when cutting its Never Rot products.

Meanwhile, the respirable crystalline silica produced by cutting fiber-cement trim poses a different sort of challenge, which James Hardie addresses through its Hardiblade, a four poly-crystalline diamond blade that’s designed to minimize particulate creation. It’s available in 7¾-, 10- and 12-inch versions. In addition, James Hardie recommends using a dust-reducing circular saw equipped with HEPA vacuum extraction.

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