Wood Flush Doors New Standards & Low-Pressure Laminates
For many architects and specification writers, excellence in product performance, not construction, is the litmus test that separates providers who offer quality products from those who don't. In response to this emerging trend, some architectural wood flush door manufacturers are shying away from traditional prescriptive standards in favor of performance standards that respond to the new technological advances in door construction.
Performance-driven standards are paving the way for a new generation of wood flush doors that, in many cases, are superior to those produced in accordance with prescriptive standards. The door industry is not alone in embracing this new construction ethic. The switch to performance-driven quality standards, for example, is become increasingly evident within the concrete and fire protection systems industries where performance standards are currently in place and have been employed successfully.
Actually, the concept of a performance-driven standard is not new to the architectural door industry and its leading trade association, the Window and Door Manufacturers Association (WDMA). The WDMA's current standard, the I.S. 1A, was preceded by the I.S. 2-A440, which established performance criteria for side-hinged exterior doors, including their ability to resist air and water infiltration and impact. In the past, architects have also incorporated in their "references" sections quality standards for wood flush doors developed by two other woodworking organizations - the Architectural Woodwork Institute and the Woodwork Institute of California. The latter sets standards for doors used primarily on the West Coast.
Unfortunately, these standards are not uniform, nor do they all emphasize performance. In fact, only the WDMA's I.S. 1A incorporates standards that will ensure reliability and longevity, as well as eye-pleasing aesthetics. There are several important changes in the 2004 edition of the I.S. 1A document, including:
The introduction of "Performance Duty Levels"
Listing of performance attributes and their values within duty levels
Publication of a suggested installation chart for each duty level
Removal of most of the "prescriptive" language governing construction methods
The addition of a section that addresses positive pressure fire doors
Introduction of a section dedicated entirely to aesthetics, including the appearance of faces and edges
References to a new face material--low pressure decorative laminates.
Since there are now three performance duty levels - each based on "frequency and severity" of product usage - it is up to each specifier to determine which duty level is appropriate for the doors on a given project. Extra Heavy Duty has the highest minimum performance values while Standard Duty has the lowest. The I.S. 1A document contains a chart that can help architects determine which duty levels are appropriate for various door installations.
Many current door specifications reference a series of performance tests developed by the WDMA. These tests are now incorporated into the I.S. 1A, 2004 edition. They include:
A cycle slam test to assess the performance of a door's hinges and closer, along with the door's overall performance during peak usage periods. In this test, a door is opened and closed at a rate of 24 cycles per minute or one cycle every 2.5 seconds. To ensure an uncushioned impact, the latching speed mode of the closer must be disengaged. A newly developed, non-prescriptive door type, subjected to a 1 million-cycle test never even required a re-tightening of the hinge screws. (The test protocol allows for an inspection of the door at least once every 25,000 cycles, at which time hardware can be lubricated and hinge screws tightened if necessary.) In order to properly inspect the door area where the hinges are attached, the hinge is removed from the door.
A hinge load resistance test to determine the ability of a wood door's vertical edge to resist the horizontal withdrawal of an attached hinge and to evaluate the various vertical edge designs, hinge types and fastening systems. According to this test, a stile and rail door may not actually require a stile if the door design can meet or exceed minimum attribute values.
A screw withdrawal test to determine the ability of a wood door component to resist the withdrawal of a screw that is perpendicular to the component.
In addition to establishing test protocols, WDMA has established engineering models that can help door manufacturers develop more than adequate minimum values. Among other things, the models simulate stress typically associated with swinging doors and help analyze load distribution at the hinge.
For years, flush door standards developed by WDMA used descriptors to help specifiers choose the door they wanted. For example, a specifier would typically refer to a "PC-5" door - a five-ply door with particle core. Under the latest version of I.S.1A, a door is specified using the performance duty level and the aesthetic grade. An example would be "Extra Heavy Duty, Premium Grade." If fire-rated doors are required, they must be clearly specified. Moreover, they must meet testing requirements established by local building codes. In many cases, these testing requirements have switched over to positive pressure. A section in the standard outlines the highlights associated with positive pressure-tested fire doors.
Specifiers should recognize that while the shift to a performance-based standard has opened the door to more innovative construction methods, there is still a role for prescriptive guidelines to achieve the desired aesthetics. Fortunately, the latest I.S.1A standard recognizes all traditional face materials, including wood veneer, medium density overlay paper for premium paint, other paintable faces for custom paint and high pressure decorative laminates.
Perhaps one of the most significant changes in the latest I.S.1A standard is the prominence given to low pressure decorative laminates (LPDL). Made from decorative laminate paper that has been saturated in reactive resins, these aesthetically pleasing facings are hot-pressed to a door surface to create a permanent bond. In fact, the paper doesn't just bond to the door, it thermally fuses to the door.
Low pressure decorative laminates resemble their high-pressure counterparts in some ways, but there are distinct differences as well. For example, most high-pressure laminates are subjected to a one-step resin bath, allowed to dry, and pressed onto a phenolic backer. The high-pressure laminate is then glued to the door core. By contrast, low pressure laminates receive a two-step, resin bath, giving them greater scratch resistance. These laminates are then "direct pressed" to the door, creating a single-ply, monolithic door.
Low pressure decorative laminates are typically applied to an engineered door core made of high-density (42 pounds) board. High-density boards are preferred for these laminates because of their improved physical properties, face screw holding power and their ability to resist sound transmission effectively.
Since low-pressure laminates do not require a phenolic backer, they are immune to stress cracking, which can occur with high-pressure laminates, especially following a strong impact, or in areas around hardware components or a vision light cutout. With no phenolic backer, low-pressure laminates also do not display an unsightly black line where the door edges and faces meet, as is the case with high-pressure laminates.
The addition of low-pressure laminates to the I.S. 1A quality standard provides architects with new prescriptive options to ensure that the wood flush doors they select meet their requirements for products that combine high performance with pleasing aesthetics.
David San Paolo is Technical Director for The Maiman Company, an architectural door manufacturer located in Springfield, MO
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