A variety of materials are used for making architectural detailing, columns, and similar millwork. Here is a closer look at each:

Composite Materials
PrimeTrim exterior and interior trim from Georgia-Pacific is an all-wood composite that is highly resistant to rot and decay and has no knots, finger joints, or defects. It is sold factory-primed on the face and two edges and is said to require re-painting less than traditional wood trim. It is made in 16-foot lengths and may have either a smooth or textured surface.

Plaster Architectural Detailing
Plaster has been used for centuries to create interesting detailing. On building exteriors, it is used for some columns, corbels, wall plaques, and other small details.

One plus for plaster is that it is all-natural; it is made from gypsum and typically reinforced with hemp.

It must be sealed for weather protection. Plaster Cast Designs, in Shelbyville, Tenn., is one company that sells an extensive line of stock parts by mail order and can custom-cast parts by request.

Polyurethane Foam
New mouldings and architectural elements are commonly made from high-density polyurethane foam. Easy to cut and fasten with standard woodworking tools, polyurethane isn’t subject to some problems associated with wood: shrinkage, expansion, warping, splintering, and decay.

Moulded detailing is usually factory finished with a UV-inhibiting primer and white acrylic finish. Components may be painted or stained with a non-penetrating stain, and, unlike finishes on wood, finishes on polyurethane tend to last somewhat longer.

Unlike wood mouldings that are often combined from several different pieces, these products are one piece, which makes them much more affordable to install than wood.

Many different components are available. The largest manufacturer of these products, Fypon, makes more than 3,500 different styles and sizes. And if you can’t find a stock piece that suits you, you can get it custom formed to your specifications. NMC Focal Point and Orac Decor also distribute a full line of products throughout the United States.

Typical products made from polyurethane include door surrounds (both complete or with separate pilasters, mantels and pediments), decorative window headers, raised panels for under windows, decorative scrollwork brackets, gable-end trim, corner trim, shutters, dentil blocks for under soffits, cornice mouldings, and more.

Many homeowners install polyurethane mouldings themselves, following the manufacturer’s instructions. These materials are cut with conventional woodworking saws (a special miter box is available for large profiles). They’re usually tacked in place with finishing nails, but special adhesives are used for joining mouldings that create joints guaranteed not to crack or separate. Small profiles are priced similarly to wood, but larger profiles are more economical because they’re made as a single piece.

For mail-order catalogs or the names of nearby dealers, you can contact the companies directly. Because the offerings are so vast, the best way to check prices is to get a catalog. Orac Decor’s most popular crown mouldings range from about $10 per lineal foot to $17 per foot. All are sold in 6 1/2-foot lengths.