Commercial Door Selection and Installation
Selecting the correct door for any building is not an open and shut case. All aspects of the door must be considered, including its usage, frequency of use, size, finish, desired durability and required safety features, including fire ratings.
When choosing the appropriate door, questions must be answered regarding its construction. Should it be aluminum, glass, steel, wood or composite? Should it be fire-rated or not? If so, what rating is required? Understanding the differences and similarities between door types allows a design professional to make an informed and accurate selection for that building.
Each manufacturer’s representative, of course, is partial to his or her own type of door. Though each type has its own merits, it’s hard to beat the beauty of a wood door, especially with the wide range of veneer cuts available today. The wide selection of face veneer cuts is best shown in the latest Architectural Woodwork Institute (AWI) quality standards section 1300, “Architectural Flush Doors”. Topics range from suggested specifications to show-through or telegraphing limitations.
When wood doors are selected on a project, there’s the opportunity to match fire-labeled doors and non-fire labeled doors. Wooden fire rated doors have come a long way in recent years. With the better selection of core, stile and rail materials, matching hardware can be used on fire labeled wood doors. In addition to its beauty, a wood door selection can come with the security and fire safety ratings often associated only with metal doors.
A basic wood door consist of a core, (the interior, core section of the door), the stiles (the vertical edges of the door), the rails (the door’s top and bottom edges), and the veneer, or the face of the door. Some manufacturers use a five-ply system, and others use a seven -ply bottom.
A five-ply system consists of the faces (each side of the door), the cross bands (between the faces and core) and the core. A seven-ply system adds veneer backs between the cross band and core, providing two face veneers, two cross bands, two veneers backs and the core.
There may be a debate about which is better, five-ply or seven-ply. In some cases, manufacturers even make a nine-ply door. The overall thickness of a 1 ¾” door doesn’t change. If more plies or layers are added, the core, stile and rail thickness must be decreased. As long as the door adheres to the quality standards of the industry, the end result - the beauty of wood grain - can be achieved with either ply construction.
Another continuing debate is about the merit of a bonded core construction vs. an edge-framed, or drop-in core construction. In a bonded core construction door, the stiles and rails are glued to the core, while sections between the faces are bonded to the stile-rail-core assembly. In an edge-framed door, they are not. Cost differences between the two types can be substantial.
Whenever possible, the door selected should meet AWI’s 1300-G-C PC5 or PC7 specifications.While the edge-framed core meets AWI’s F PC7 specification, it does not meet the 1300 G-C PC5 or PC7 specification. In most cases, the edge-framed core constructed door should only be used if budget constraints prohibit the use of a bonded core door.
Wood doors also are available in design that can control the spread of fire for 1 ½ hours or more. These wood fire doors often are placed on openings leading from a corridor to an office, janitor closet, storage room, stairwell or any other opening that penetrates a fire barrier wall. The majority of architectural grade wood doors are manufactured to carry a 20-minute fire rating, giving them the ability to hold-off fire for a minimum of 20 minutes.
Selection of all wood doors should come from a quality architectural wood door manufacturer who meets or exceeds the Quality Standards of the Architectural Woodwork Institute or the National Window and Door Association (NWDA). These organizations provide minimum standards for the construction and quality of wood doors and either group can provide the design professional with criteria needed for proper selection of wood doors for any project.
Wood doors should not be used in any area where the amount of use could cause enough damage to call for frequent replacement. In these cases, select a hollow metal steel door. Also, whenever a three-hour (A label) fire door is required, the door must be steel.
As with other fire-rated materials, wood doors are rated by Underwriters Laboratories (UL) and Warnock Hersey (WH). Both companies provide ratings that specify the door’s fire protection capabilities, as well as the rating for hardware to be installed on these doors.
The National Fire Protection Association’s NFPA 101 Section 5 is a complete overview of the ratings required for a specific fire door in a specific use, and the hardware requirements for that door. NFPA 80 applies to the use, installation and maintenance of fire doors, windows, glass blocks and shutters. In the past, the selection of wood fire doors, especially the selection of accompanying hinges and hinge placement, has been a stumbling block for design professionals. Until recently, hinges were surface applied to the door with through bolts. With the advent of special laminate materials (or the Georgia Pacific type constructions), the hinges can be mortised into the door, eliminating the half-surface hinges with through-bolted black plates.
A surface applied hinge might be visually acceptable on the hinge leaf side of the door. However, take a look on the “push” side of the door (usually the public side). You may see either the grommet nuts or a backing plate with grommet nuts showing. These are often required to properly support the weight, and frequency of use of the door. Full mortise hinges provide the best visual appearance because the backing plates would not be required, but in many cases would not be the appropriate hinge type to use if the stile were not adequate to hold the screws used in a full mortise hinge application. Door design and construction that includes adequate stile construction for installation of full mortise hinges should be considered to avoid the unsightly appearance of the backing plates and grommet nuts on an otherwise beautiful door or door pair.
Some manufacturers who supplied laminated cold wood doors prefer not to square the corner of the hinge mortise because the plastic laminate will crack in the corners. When plastic laminated wood doors are machined in the field, you can find round corners on all the hardware mortises. In this case, perhaps a half-surface hinge would acceptable, but only with a backing plate finished to match the hinges.
In the construction of wood fire doors, the weakest point is the bending of the veneer, stile/rail and core. Construction failure, if and when it occurs, usually is on the hinge side of the door.
Both UL and WH use time-related ratings that specify how long fire has been tested to be contained on one side of the door. Ratings include a 1 ½ hour “B” label, used in openings in two-hour enclosures such as stairs (will usually carry a time rating greater than the door time rating), a one-hour “B” label (used in openings in one-hour enclosures such as stairs and mechanical rooms), a ¾ hour “C” label (used in openings in corridors and room partitions), and a 20- minute label (used where smoke control with limited fire protection is required). Local building codes and the authority having jurisdiction decide what fire rating applies to what opening in new construction projects. The design professional is responsible for indicating the required rating for each door opening according to the door’s usage and applicable codes.
Most suggested fire doors are 1 ¾” thick, with the material for the core varying according to the fire rating. For example, the construction of a 20-minute fire door consists of the door skin, or veneer, a high-density particle board core, or staved lumber core and the stile and rail system. The stile can be soft wood, matching hard wood or a special laminated material without a wood edge.
The construction methods of 45-minute or 60-minute fire-label doors are similar to each other, but different from 90-minute doors in the stile and rail construction. The cores of these three types of doors are the same, but the stile of the 90-minute labeled wood door is required to have a plastic laminated insert between the stile and the core.
In many cases, it’s necessary to machine wood fire doors, or to make cutouts for hinges, locksets, fire exit hardware, lights and louvers. To maintain the door’s fire rating, any cutouts must be made in a door manufacturing plant or certification and listing shop approved by the labeling authority. Wood fire doors only can be machined for hardware or any other modifications for which the manufacturer is approved. A Listings Manual published by the labeling authority will provide details.
Whenever glass lights are required in wood doors and some of the doors are labeled, select the same design steel glass light kit to be used on labeled and non-labeled doors, regardless of what the door is made of. Be sure the door edge dimension from the edge of the door to the glass light is the same for labeled and non-labeled doors. This edge dimension of wood doors is five inches from the edge of the door or from the edge of the hardware cutout to the edge of the glass light cutout.
Most wood door manufacturers adhere to the Warnock Hersey criteria for fire doors. This procedure is available to certified wood door distributors to allow machining of wood fire doors on their own premises, from Warnock Hersey stock. Warnock Hersey provides in-house inspection to ensure its criteria is upheld.
In most cases, a modifications shop buys the wood fire doors from the manufacturer in a flat slab state, with no hardware, light or louver cutouts. The doors then are machined for the appropriate hardware, affixed with the necessary label and shipped to the job site.
By definition, an exterior door cannot be controlled on both sides for temperature and/ or humidity. When the wood fire door is cut for glass lights, louvers and/ or hardware, moisture can enter the core area of the door and cause the core and door to fail. Wood fire doors should never be specified on exterior openings. Most manufacturers will not extend any warranty or guarantee on such an application.
The fire rating of a wood fire door must be taken into consideration when selecting hardware for the door. Only hardware certified and approved by the fire-ratings services can be used on a wood fire door. The basic rule for hardware here is that it must be self-closing and self-latching.
Each type of door has its own merits. More often, wood doors offer both usefulness and beauty. Whether the wood door is painted, stained or with natural finish, they often appeal to the eye and have more usefulness today, with regard to fire protection and life safety, than in years past. A well selected, professionally installed wood or steel door that is appropriate for the fire rating for that opening will result in an installation that is both beautiful and compliant for your commercial building applications.