DOORS

Doors fall into two general categories, exterior and interior. Weather resistance is usually the most important functional factor in choosing exterior doors, whereas resistance to the passage of sound or fire and smoke are frequently important criteria in the selection of interior doors. Many different modes of door operation are possible (Figure 18.23).

There are numerous types of exterior doors: solid entrance doors, entrance doors that contain glass, storefront doors that are mostly or entirely made of glass, storm doors, screen doors, vehicular doors for residential garages and industrial use, revolving doors, and cellar doors, to name just a few. Interior doors come in dozens of additional types. To simplify our discussion, we will focus on swinging doors for both residential and commercial use.

Wood Doors

At one time, nearly all doors were made of wood. In simple buildings, primitive doors made of planks and Z-bracing were once common. In more finished buildings, stile-and-rail doors gave a more sophisticated appearance while avoiding the worst problems of moisture expansion and contraction to which plank doors are subject (Figures 7.23 and 7.24). The panels are not glued to the stiles and rails, but instead “float” in unglued grooves that allow them to move. The doors may be made of solid wood or of wood composite materials with veneered faces and edges. In either case, they are available in many different species of woods.

In recent decades, stile-and-rail doors have continued to be popular in higher-quality buildings. However, flush doors have captured the majority of the market, chiefly because they are easier to manufacture and therefore less costly. For exterior use in small buildings, and for both exterior and interior use in institutional and commercial buildings, flush doors are constructed with a solid core of wood blocks or wood composite material (Figure 7.24). Interior doors in residences often have a hollow core. These consist of two veneered wood faces that are bonded to a concealed grid of interior spacers made of paperboard or wood. The perimeters of the faces are glued to wood edge strips. Flush doors with wood faces are also available with a solid mineral core that qualifies them as fire doors.

Flush wood doors may be manufactured and specified according to any one of several industry standards for door appearance and durability, the most commonly used of which is the Window and Door Manufacturers ANSI/WDMA I.S.1-A-04 Architectural Wood Flush Doors. This standard includes three performance grades—Standard Duty, Heavy Duty, and Extra Heavy Duty—intended for doors used in applications of increasingly heavy usage, as well as varying appearance grades that control the quality of face veneers.

FIGURE 18.23 Some modes of door operation.

FIGURE 18.24 Some typical configurations for wood doors. The top row consists of flush doors. The middle row is made up of stile-and-rail doors.

A relatively recent development is a door made of wood fiber composite material that is pressed into the shape of a stile-and-rail door. Usually, the faces of the door may be given an artificial wood grain texture or faced with real wood veneer.

Entrance doors must be well constructed and tightly weatherstripped if they are not to leak air and water. Properly installed and finished wood panel or solid-core doors are excellent for exterior residential use (Figures 6.14 and 6.15). Pressed sheet metal doors and molded GFRP doors, usually embossed to resemble wood stile-and-rail doors, are popular alternatives to wood exterior residential doors. Their cores are filled with insulating plastic foam, making their thermal performance superior to that of wood doors. They do not suffer from moisture expansion and contraction, as wood doors do. They are often furnished prehung, meaning that they are already mounted on hinges in a surrounding frame, complete with weatherstripping, ready to install by merely nailing the frame into the wall. Wood doors can also be purchased prehung, although many are still hung and weatherstripped on the building site. The major disadvantage of metal and plastic exterior doors is that they do not have the satisfying appearance, feel, or sound of a wood door.

Residential entrance doors almost always swing inward and are mounted on the interior side of the door frame. This makes them less vulnerable to thieves who would remove hinge pins or use a thin blade to push back the latch to gain entrance. In cold climates, it also prevents snow that may accumulate against the door from preventing the door from opening. For improved wintertime thermal performance of the entrance, a storm door may be mounted on the outside of the same frame, swinging outward. The storm door usually includes at least one large panel of tempered glass.

In summer, a screen door may be substituted for the storm door. A combination door, which has easily interchangeable screen and storm panels, is more convenient than separate screen and storm doors.

Steel Flush Doors

Flush doors with faces of painted sheet steel are the most common type of door in nonresidential buildings (Figure 18.25). For economy, interior steel doors in many situations have hollow cores. Solid-core doors are required for exterior use and in situations that demand increased fire resistance, more rugged construction, or better acoustical privacy between rooms.

Metal doors and most nonresidential wood doors are usually hinged to hollow steel door frames, although wood and aluminum frames can also be used. Many different types of anchors are available for mounting frames to partitions of various materials (Figure 18.26). Where hollow metal door frames are installed within masonry walls, they may be filled with cementitious grout to improve sound deadening and to make the door frame more resistant to tampering or forced entry.

Steel doors and frames are commonly manufactured and specified according to one of two standards: the Steel Door Institute’s ANSI/SDI A250.8 Recommended Specifications for Standard Steel Doors and Frames or the Hollow Metal Manufacturers Association’s ANSI/NAAMM-HMMA 861 Guide Specifications for Commercial Hollow Metal Doors and Frames. The first of these is intended for standard steel doors, manufactured to a standardized set of sizes, configurations, and quality levels. The second standard is for custom steel doors, those generally manufactured to a high quality standard in custom sizes and configurations.

FIGURE 18.25 Some typical configurations for steel doors.

FIGURE 18.26 Details of hollow steel door frames. The lettered circles on the elevation at the upper left correspond to the details on the rest of the page.

Fire Doors

Fire doors have a noncombustible mineral core and are rated according to the period of time for which they are able to resist specified time and temperature conditions, as defined by NFPA 252 Standard Methods of Fire Tests of Door Assemblies, or by several similar tests defined by Underwriters Laboratories. In general, doors within fire-resistance-rated walls must themselves also be fire rated. However, because doors constitute only a limited area of most walls, and because combustible furnishings or materials are not normally located directly in front of door openings, the required fire resistance rating for fire doors is often less than that required for the walls in which they are located. Figure 18.27 gives fire resistance ratings for fire doors as required by the International Building Code (IBC). For example, a door in a 2-hour rated exit stairway enclosure must be 1½-hour rated, a door in a 1-hour rated exit stairway enclosure must be 1-hour rated, and a door in a 1-hour rated exit corridor must be 20-minute (⅓-hour) rated. Doors in walls that are 2-, 3-, and 4-hour fire resistance rated, such as those separating uses within a building or separating buildings from one another, must be 1½- or 3-hour rated. A standardized label is permanently affixed to the edge of each fire door at the time of manufacture to designate its degree of fire resistance. (The building code requires that these labels not be painted over during construction so that the fire rating of the door can always be verified during subsequent building inspections.)

Glass used in fire doors must itself be fire rated (see the previous chapter) so that it will not break and fall out of the opening for a specified length of time when exposed to the heat of fire. The maximum size of glass may also be restricted, depending on the fire classification of the door and the properties of the particular type of glass used. Like glass in any door, glass in fire doors must also meet the requirements of safety glazing so that if broken, it does not create life-threatening shards.

Egress Doors and Accessible Doors

Many doorways act as components of a building’s egress system, the path that occupants take when exiting a building during a fire or other emergency. Building codes require that such doorways be sufficiently wide to allow occupants to exit in a timely manner, with the width of any particular door dependent on the number of occupants served. For ease of operation, most egress doors must be side-hinged, they must not be too large, and when equipped with closers, they must not require too much force to swing open. The International Building Code requires egress doors serving 50 or more building occupants, as well as doors serving Hazardous Occupancy spaces, to swing in the direction of egress travel so that they do not become impediments to occupants attempting to exit quickly. Other building codes have similar requirements. Even when locked, egress doors must remain readily openable from the side from which occupants may approach the door when exiting. To ensure the simplest possible operation under emergency conditions, some egress doors are required to be fitted with panic hardware, horizontal bars or similar devices installed across the face of the door that unlock and unlatch the door whenever the bar is depressed.

FIGURE 18.27 Required fire resistance ratings for doors according to the International Building Code. (Portions of this publication reproduce tables from the 2006 International Building Code, International Code Council, Inc., Washington, D.C. Reproduced with Permission. All rights reserved.)

Doorways along buildings routes that must be accessible to persons with disabilities must meet requirements for minimum width, ease of operation, maximum height of sill, and adequate clearance for approaching and opening the door.

There are many types of special-purpose doors. Among the most common are X-ray shielding doors, which contain a layer of lead foil; electric field shielding doors, with an internal layer of metal mesh that is electrically grounded through the hinges; heavily insulated cold storage doors; and bank vault doors.