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Everybody is busy these days, so it's no surprise that durable, low-maintenance exteriors have become increasingly popular with homeowners. However, traditional exterior decorative millwork and trim that is constructed of wood has limited rot and weather resistance in many climates. One alternative is high density, plastic trim, which is more durable and has a lower installation cost than wood. It can be molded into shapes and profiles that resemble more expensive hand-carved wood or multi-layered moldings.
There are several types of plastic material used to make exterior trim. High density, polyurethane is the most common material used to mold decorative, synthetic exterior trim. Although it is most popular for exterior window and door surrounds, it is also produced in profiles for fascia, friezes, balustrades, and numerous flat and curved profiles. It can also be used for home interiors. One manufacturer even produces a fascia molding that has special air intake vents for attic ventilation. Another plastic material is polyvinyl chloride (PVC) that is formed into boards and profiles.
Plastic trim products vary in formulation and density. The higher density products are more dimensionally stable, stronger, and indentation resistant, but are also more expensive. Plastic trim is normally sold primed and ready for paint, or a stain for a simulated wood finish. PVC trim is less costly than polyurethane, but its surface must be lightly sanded prior to painting.
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Plastic is not susceptible to rot and swelling, providing a long lasting décor for homes.
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By reducing the chances for decay, there is less danger of the trim coming loose or exposing the house to the elements.
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Plastic trim is available throughout the United States from manufacturers and local distributors.
Material cost is slightly higher than pine trim and molding. However, because less preparation must be done to the material, labor costs can be less than for pine and other wood trimmings.
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Some manufacturers use a fire-resistant coating on their plastic trim to meet flame-spread requirements for certain building types.
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Installing plastic trim is very similar to wood molding, and with few exceptions uses the same process, tools, and fasteners. Since the molding is often too large to fit into a standard miter saw, a relatively inexpensive miter box must be used. When splicing pieces together on long runs, a "butt" joint (molding cut with square ends) is used instead of a "miter" (molding cut with a 45 degree bevel) common with wood moldings. Unlike wood corners, plastic exterior molding is mitered, not coped (cutting one piece of molding with a "coping" saw to match the contour of the adjoining piece). Frequently, complex wood moldings require several different layers of material. Plastic trim can be installed as a single piece, which simplifies installation and reduces labor cost.
Adhesives are typically used to attach plastic trim, although nails may be used to attach molding to a wall temporarily until the adhesive has hardened. Adhesive is placed on all joints (corners and splices) to prevent gaps from opening during the life of the structure. Nail holes, gaps, and indentations can be filled with any suitable filler. The same trade contractors that install traditional wood molding can install plastic trim.
Warranties stretch from 1 year to lifetime warranties against rot and infestation, depending on manufacturer. Some are transferable among homeowners. Additionally, some manufacturers may offer up to 15 year warranties against color change.
Plastics used for this type of trim are not subject to bacterial rot, and they do not shrink or swell like wood. Resistance to indentation is said to be about the same as pine. Painted finishes on plastics are generally more durable than on wood because of their stable moisture content. Plastic trim is easy to cut, plane, and shape. It can reduce labor significantly when installing decorative trim instead of several layers of wood molding. Although wood molding frequently requires flashing to protect them from rainwater, some manufacturers of plastic trim do not recommend flashing their materials, which provides additional savings in labor and materials. Depending on the complexity of the molding, an installer can save from 10 to 50 percent over wood moldings
Plastic trim and moldings are new to many installers, so they must learn to use the special miter box and adhesives correctly. Some moldings may not be available locally, and some manufacturers have order lead times of greater than one week. Therefore, purchasers must be careful to order the correct amount and installers must minimize mistakes during installation for on-time project completions. Plastic trim is more readily available.
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