by Beth Kraus, CSI, CDT
Whether one is trying to replicate the ornate trimwork from a 19th Century southern plantation or trying to seamlessly replace exterior molding on a 1972 ranch-style home, polyurethane plastic millwork products can be the answer. Widely used for both historical and contemporary residential and commercial renovation projects, these urethane plastic components have gained in popularity since their introduction several decades ago.
With the advent of urethane plastic millwork in the 1970s, high-density polyurethane plastic’s durability and versatility made it competitive with more traditional materials for applications both inside and out. Additionally, these urethane plastic products can resist moisture, humidity, warping, splitting, splintering, insect infestation, and extreme temperature changes.
Specifying the urethane plastic spectrum
Urethane plastic products, which come with a factory-applied ultraviolet (UV) ray-resistant topcoat, may be painted with any good quality latex or oil-based paint. They also accept decorative faux finishes well, such as marbleizing, washing, and texturizing. (These can be especially appealing on products such as round and oval ceiling domes, wall niches, and moldings.)
Urethane plastic products range from louvers and moldings to columns and decorative millwork, with plastic products in both structural and nonstructural categories, such as window/door trim, gable vents, porch posts, and balustrades. From ornate brackets to faux beams to door pediments, urethane plastic manufacturers have a wide variety of plastic products ideally suited for both residential and commercial projects when it comes time to think about renovation work—or subtly replacing damaged components made from more traditional materials.
The high-density urethane plastic is manufactured using a two-component rigid polyurethane foam plastic system and has a closed-cell structure that can resist water penetration and absorption. (For more information, see “Making Urethane Products.”)
Rigid polyurethane plastic’s durability is due to its status as a thermoset plastic material—in other words, once the reaction has taken place to form the plastic polymer, it cannot revert to its original components with just heat being applied. This means increasing the temperature of the polyurethane plastic—within reason—does not cause it to melt or significantly lose its structural properties. Generally, rigid polyurethane foam plastics have good dimensional stability (including resistance to volume change in extreme ambient temperature conditions) due to the strong polymer network created when the foam plastic is produced. Additionally, polyurethane foam plastic has a low coefficient of thermal expansion and contraction, which can make it suitable for many temperatures.
With urethane plastic, each piece has a consistent quality and finish, so there are no wasted materials and on-site installation is easily accomplished. Compared to decorative trim products made from traditional materials, urethane plastic millwork generally has lower overall product and installation costs. Furthermore, as urethane plastic products require no sanding, priming, or sealing, they can also allow for labor savings. While raw material costs for urethane plastic’s traditional counterparts may be lower than polyurethane foam plastic, labor costs for product installation and maintenance of these traditional products is generally higher.
Capabilities of urethane plastic millwork
Architects and designers interested in specifying urethane plastic products for renovation projects can find support on the Web sites of various urethane plastic manufacturers.1 Specially created design programs exist from all major plastic product suppliers, with several offering design configurators, computer-aided design (CAD) programs, and architectural binders. Additional resources include industry-standard calculators (for radius, rake, and bevel miter cuts) and the ability to create elevations and assemblies.
Urethane plastic millwork pieces can replicate intricate patterns on ceiling medallions or contain smooth lines on moldings. For renovation projects, one of urethane plastic’s chief assets is ability to gain highly detailed, authentic looking reproductions of historic products. Some heavy, ornate, plaster ceiling medallions can be replicated in a urethane plastic piece weighing less than 0.45 kg (1 lb). For those projects requiring the ‘look’ of traditional materials, many manufacturers offer stainable urethane plastic moldings containing authentic wood grains.
The closed-cell structure of urethane plastic products can make them suitable for high humidity areas of the home, such as bathrooms, kitchens, and laundry rooms. Wall niches, moldings, and brackets are popular in these rooms because they neither warp nor twist when exposed to excessive moisture. Throughout the rest of the home, urethane plastic products can be found as window and door trim, ceiling domes, faux beams on ceilings, and as one-piece mantel surrounds. Low-maintenance urethane plastic shutters, louvers, and entryway surrounds are extremely popular on the exterior of residential projects and are generally available in dozens of styles complementing all major designs.
Non-residential renovation applications of urethane plastic products are abundant. From refurbishing classic millwork in restaurants, offices, and healthcare centers to replacing balustrade systems in college dormitories, nursing homes, and hotels, urethane plastic is selected for a wide variety of commercial projects worldwide. What once may have been an arduous task of specifying historically accurate reproductions of moldings can now be accomplished relatively quickly. Urethane plastic companies offer architectural profiles in everything from uncluttered to ornate designs. Suitable for both interior and exterior use, there are hundreds of decorative urethane plastic millwork options including corbels, ceiling domes, acorns, wall niches, and brackets.
Available in lengths up to 4.9 m (16 ft), urethane plastic moldings range from simple 51-mm (2-in.) tall pieces to intricate built-up combinations more than 0.3 m (1 ft) high. Hundreds of profiles exist to replicate an array of designs and styles. Some of the most popular plastic moldings include dentil profiles, cornice-and-cove, crowns, chair rails, and window/door trim. More elaborate egg-and-dart, crown leaf, ribbon-and-bow, Florentine, and scalloped plastic molding profiles are also available. Special collections of styles, including Victorian, arts-andcrafts, southwest, and contemporary moldings and millwork are also available, as well as accessories including miterless corners, plinth blocks/rosettes, keystones, and molding divider blocks.
Whether one is trying to replicate a molding pattern from an 1812 Federal-style inn or create a unique design element of a mallard for the entryway of hundreds of hotel rooms, urethane plastic manufacturers have the ability to support custom design needs. Once patterns and designs are finalized, special plastic molds can easily be created at the production facility and pieces formed to fit the project’s exacting requirements.
Specifiers can take advantage of urethane plastic’s custom capabilities by requesting fabricated pieces for door entries and windows. The in-house fabrication shop at urethane plastic production facilities can customize pieces for oversized openings or with specific design preferences. Specifying the mixing and matching of pieces from a product catalog can result in the manufacturer creating customized window and door enhancements, saving job-site time and labor.
One innovation applauded as a time saver by both specifiers and installers is the urethane plastic eave vent system, which acts as both a decorative molding profile and a functional vent that can prolong roofing shingle life. Structures using these plastic fabricated systems often contain functional louvers—a combination of urethane plastic louvers featuring slats with steep 45-degree angles that also include non-corrosive screens to help keep insects out while allowing airflow.
Limitations and building codes
Many urethane plastic products are solely created for decorative use and have little structural integrity. The exceptions are porch posts, balustrade systems, and columns constructed with fiberglass, polyvinyl chloride (PVC) plastic, and/or steel support interiors. (Since there is no distinct advantage of any of these structural materials when used in conjunction with u rethane plastic, the support material is determined by the application and manufacturer.)
Some companies conduct independent testing by certified laboratories for load-bearing capabilities on these structural products. While many manufacturers follow International Building Code (IBC) guidelines for testing of rail systems, there are no specific guidelines for load-bearing capabilities on structural products. Some manufacturers test these pieces to a load at which the amount of force being applied stops increasing and levels off. From that number, a safety factor of 1.75 to 2.00 is used to come up with the load capacity.
Specifiers will find most urethane plastic products produced by manufacturers can safely be used in accordance with rulings from the International Code Council’s (ICC’s) I-codes and the National Fire Protection Association (NFPA). Some plastic balustrade systems meet the National Building Code’s (NBC’s) 1993 Criteria (1615.8.2 Guard Design and Construction and 16184.108.40.206 In-Fill Areas) when assembled according to manufacturer guidelines. These codes are met based on the way the plastic balustrade system is assembled, not necessarily on the urethane plastic product itself. Manufacturers assemble the plastic balustrade systems according to the installation guidelines they share in their catalogs and then test these same systems to check that urethane plastic pieces comply with code rulings.
While urethane plastic millwork products are suitable for varied climates, they should never be stored for long periods in extreme heat as they can expand and contract slightly when heated and cooled. Should the products be exposed to intense heat for extended periods of time, they can become distorted and warp. Most urethane plastic millwork can withstand about 60 C (140 F), but in prolonged exposure to temperatures beyond 93 C (200 F) can result in the deterioration of the polyurethane foam plastic’s physical properties. One of these aspects may be the blistering of the urethane plastic product ’s surface—an incident especially prevalent when the plastic product has been painted a dark color that absorbs the heat. However, since polyurethane plastic foam is a thermoset plastic, it does not melt in extreme temperatures—the worst-case scenario is deterioration and possible blistering.
As with most plastic building products, urethane plastic foam pieces should acclimate for approximately 24 hours in their installation environment prior to application. Due to the temperature warping described above, a special consideration for urethane plastic millwork is that it should never be specified in an area subject to solar temperature buildup, such as behind a storm door.
While some plastic manufacturers are currently working toward meeting the flame-spread tests in ASTM International E 84, Standard Test Method for Surface Burning Characteristics of Building Materials, most urethane plastic millwork products are not specifically formulated for fire resistance.
Therefore, specifiers are encouraged to check with individual manufacturers for flame-resistance restrictions and special product orders that meet Class 1 ratings. In all cases, local building codes should be consulted and followed when using urethane plastic or any other building product in a project.
Case studies and examples
While the primary use of urethane plastic products is for decoration, there are many cases where plastic millwork pieces are specified to solve challenging design problems. For example, to help create a stately exterior for a Providence, Rhode Island, assisted living center, the design team specified an expansive array of urethane plastic balustrades, corbels, and detail work on the building exterior. The urethane plastic foam pieces transformed the three-story structure and added both the necessary structural and decorative accents to replicate an old-time mansion. In a similar situation in St. Louis, Missouri, a designer challenged with replicating cracked and decaying plaster molding in a historic hotel ballroom turned to urethane plastic building products. The plastic manufacturer was able to create a perfecthistoric match to the existing millwork. In an unusual twist, the urethane plastic product was added to the room in various sections while original plaster pieces were also left in place. The result is a space using both plaster and urethane plastic millwork with differences that are difficult to see.
In Atlanta, Georgia, an interior designer chose to use urethane plastic products in the renovation of her own home after specifying them on projects for clients. After transforming her master bedroom with a new urethane plastic trey ceiling, she added faux-finished crown molding to hide accent lighting at the base of the ceiling and then a second level of stark-white molding a foot lower on the wall for contrast. While remodeling her master bath, the same designer surrounded both her shower and soaking tub with sets of pilasters and crossheads to ‘frame’ her settings.
To make life easier for his beachfront customers, one builder in Avalon, New Jersey, surrounded the exterior of dozens of windows with urethane plastic molding and trim. The Dutch Nantucket-style home sits directly on the water and is continually exposed to sea air and salt spray. Exposure to such elements would mean repeated scraping and repainting on traditional trim products. However, the use of urethane plastic helps minimize opportunities for rot, decay, and degradation caused by harsh weather.
One reason why urethane plastic balustrade systems are so popular is because the balusters are reinforced with fiberglass or aluminum, while rails and newels have PVC plastic reinforcements and porch posts have steel reinforcements. The balustrade pieces are made with non-corrosive parts that are hidden to provide a clean, classic appearance from any angle—they can maintain their design aesthetic without the heavy demands of ongoing maintenance.
There can also be other advantages—for Toledo, Ohio’s Owens Illinois building, the design team consulted to update the look of the structure was challenged with replacing outdated can lighting. However, since replacing the lights meant disturbing asbestos and gypsum wallboard, the team decided upon a stepped-trim urethane plastic molding that simply covered the old fixtures and eliminated the need to remove the asbestos. Additional complementary urethane plastic moldings were used on the building exterior to tie it together with the interior design.
1 Specifiers interested in gaining more information on the urethane plastic industry can also find weekly updates from Urethane Update—Polyurethane Abstracts. This online newsletter, available at www.pu2pu.com, offers information on the latest patents, technical papers, product information, and technical aspects affecting the urethane plastic industry.
Beth Kraus, CSI, CDT, has been working with architects and specifiers for more than 20 years as a representative for various building product manufacturers. Since 2001, she has been a district sales manager for urethane millwork manufacturer, Fypon. Kraus is a member of the Construction Specifications Institute (CSI) and the American Society of Interior Designers (ASID) and is currently working toward her certified construction product representative (CCPR) designation. She can be contacted via e-mail at email@example.com.