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Door (Wood)

A door is a movable barrier that closes off a doorway, which is an opening in a wall through which people and their possessions must pass in order to enter or leave a house or go from one room to another. Most doors swing on hinges, or butts, fastened to one side of the door. A few doors—mainly closet and wardrobe doors in modern houses, but also large living- room and dining-room doors in older or more expensive dwelling—slide sideways, on special tracks, to open and close A door fits closely into an especially constructed frame that forms the sides and top of the doorway. The construction of this framework is much the same for all doors, both hinged and sliding, and regardless of the size or quality of the door (see Fig. 1). The two sides of the frame are the side jambs; in a hinged door, they are sometimes called the butt and lock lambs, according to function. The top of the frame is the head jamb, or simply the head. The jambs are surrounded by casing, which is decorative wood trim that sets off the doorway and also covers the gaps that exist between the jambs and the adjacent wall construction.

An interior hinged door also has a projecting strip of wood, a doorstop, nailed all around the perimeter of the doorway against which the door abuts. The door must have something to knock up against when it closes, otherwise it will simply keep on swinging, which will pull the butts out of the jamb after a while. In an exterior door, the doorstop consists of a rabbet cut about in. deep all around the side and head jambs.

An exterior door will also have a sill installed at the bottom of the doorway. The sill is a raised, sloping piece of wood, stone, or concrete that's about as wide as the jambs. Its function is to prevent rain entering the building past the bottom of the door. An interior doorway leading into a bathroom will usually have a sill installed also, especially if the bathroom floor is tiled, to prevent any water that overflows onto the floor from running out the door. Most exterior doors will also have a threshold attached to the sill. This is a thin strip of wood or metal that's about as wide as the door is thick that further closes off the gap at the bottom of the door. So much for basic nomenclature.

Fig. 1. Detail of an interior door installation, showing doorstop (U.S.Forest Service).


An enormous range of door styles and sizes exists. These doors are made from a wide variety of woods and wood products that vary greatly in quality, in the way they are manufactured, and in the way they are fastened to each other to form the finished door. The price range of doors is correspondingly wide. What follows, therefore, can be only a broad introduction to the principal types of doors that are available.

Doors are basically of two types—panel and flush. Panel doors consist of a wood framework in which are installed thinner wood panels. A panel door can have any number of panels, which are arranged in standard patterns (see Fig. 2). Flush doors are just that, perfectly flat on both sides, without any inset paneling or raised decorative trim to break the surface. Panel doors are used mainly in houses built in a traditional style, and flush doors are usually installed in dwellings built in a modern style.

Fig. 2. Types and styles of doors. In the paneled doors, the panels can be held in place either by grooves cut into the stiles or by separate moldings nailed to both the stiles and rails.

Panel Doors

Figure 2 also shows the construction of a typical panel door. The door has a vertical member on each side called a stile. The stiles run the full length of the door. The stile to which the butts are attached is known variously as the hinge, butt, or hanging stile. The other stile is the closing or lock stile. There can also be one or more intermediate stiles, but if there are, they’ are generally smaller and they never run the length of the door.

The horizontal members are called rails. There are always at least two rails, one at the top and the other at the bottom of the door, the bottom rail usually being much wider than the top rail. There can also be one or more intermediate rails, which run from one stile to the other and join them together more securely. These are known as cross rails. The cross rail in which the lock is installed is also called the lock rail. The greater the number of rails, the less tendency the door will have to sag as it gets older.

The open spaces between the stiles and rails are filled by thin wood panels. These panels may be held in place in either of two ways. The edges of the stiles and rails can be plowed (that is, grooves are cut into them) to receive the panels, the entire door then being assembled together at the same time; or the panels can be held in place by moldings nailed to the already assembled stiles and rails. These moldings are called sticks in the trade, and their installation is called sticking or stickering.

The stiles and rails of panel doors may be constructed of solid pieces of lumber or veneered plywood. Paneled doors made of solid wood aren't considered to be of the highest quality. They are used, rather, when the door is to be painted. Better-quality doors intended be stained or varnished are made from hardwood veneers. It is possible to make a panel door completely from solid pieces of hardwood, of course, but such doors have a bad tendency to warp. Veneered plywood is an excellent material as it combines the attractive appearance of hardwood with the strength and dimensional stability of plywood.

The stiles of a veneered plywood door are edged with matching hardwood strips that are 1/2 to 3/4 in. thick. The presence of these strips allows the carpenter to plane down the sides of the door to obtain a close fit in the doorway without destroying the appearance of the door.

As for the panels, they may also be made either from a solid piece of wood or from veneered plywood. Again, veneered plywood is preferred because it's dimensionally more stable than solid wood, which has a tendency to split or shrink in its frame. But, if the panels are to have raised faces or beveled edges, and if the door is to be stained or varnished, the panels must be made from a solid piece of wood.

Paneling is always set loosely within its frame. It is never glued, nailed, or otherwise fastened to the frame. To do so would not allow the frame or the paneling to swell or shrink in response to normal changes in humidity, and it's likely that the panels would warp or crack in time.

Flush Doors

Flush doors are constructed basically much like ordinary ply wood panels (see PLYWOOD). The doors, however, have much thicker center cores. There are two main types of core used— those that are of solid construction and those that aren't (see Fig. 3).

Hollow-Core Doors

Hollow-core flush doors are used inside a house, where the temperatures are equitable and the humidity stable throughout the year. Under these conditions, there isn't much danger that these lightly-constructed doors will encounter any unusual stresses that will cause them to warp.

A hollow-core flush door will have a framework of stiles and rails made usually of ponderosa pine. On less expensive doors meant to be painted, the stiles will remain exposed. On better- quality doors meant to be stained or varnished, the stiles will have veneer strips glued over them that match the face veneer used on the side panels. On the best-quality doors, solid hardwood strips 1/2 to 3/4 in. thick are glued to the stiles.

Hollow-core flush doors also require solid blocking into which mortises for the door locks can be cut. These lock blocks are glued to the stiles and are anywhere from 20 to 27 in. long and 4 to 4 5/8 in. wide—plenty of room in which to locate a lock. Less expensive doors will have a lock block built into only one edge of the door, and the carpenter had better not bore into the wrong edge. More expensively made doors will have a lock block installed along each of the edges of the door.

The center core space may be filled with any of a wide variety of lightweight materials in themselves flimsy but which, when glued to the facing panels, increase the strength of the door tremendously. The same principle is used in modern aircraft construction. Some of the most common of these fillers which is then planed down as a unit to its final thickness. In other doors, the core blocks are merely laid in place and glued not to each other but to the face panels. White pine was once widely used for core blocks because of its lightness and dimensional stability but ponderosa pine is used nowadays, as it has the same qualities.

Each side of the door is faced with a one- or two-ply hardwood veneer. If one-ply panels are used, they will be 1/8 to 1/4 in. thick. If two-ply panels are used, the inner ply will usually be 1/8 in. thick, and the outer ply will be from 1/16, to 1/8 in. thick. Laminates printed with a simulated wood pattern or in bright colors are being used increasingly for the face plies are shown in Fig. 3.

Fig. 3 (a, b). Flush doors are manufactured with many different types of core construction. (National Woodwork Manufacturers Association).


Occasionally an architect may design an elaborate entrance door for an expensive dwelling, which must be especially made, but apart from this rarity doors nowadays are stock doors, that's , they are mass produced in standard sizes and installed by a carpenter “as is.” Table 1 shows the wide range of stock-sized flush doors that are made; one can find in the table almost any combination of width, thickness, and height one would ever need. If a customer should want an odd-sized door, most mills would make the door to order but would charge a premium, of course. Despite the complexity of Table 1, most doors are made in only a few popular sizes, which are as follows.

Interior doors are usually 1 3/8 in. thick, the major exception being small closet doors, which are often only 1 1/8 in. thick. Interior door heights are usually 6 ft 8 in., for both first-floor and upper-floor doors, though sometimes the upper-floor doors are only 6 ft 6 in. high. Interior door widths are usually 2 ft 6 in., except for bathroom doors (which may be 2 ft 4 in. wide) and clothes-closet and linen-closet doors (which may be 2 ft 0 in. wide).

Exterior doors are usually 1 in. thick, 6 ft 8 in. high, and 3 ft 0 in. wide, although service-entrance doors may be only 2 ft 8 in. wide. These are the usual minimum dimensions. Many main entrance doors will be larger than this—doors 7 ft 0 in. high and from 2 to 2¼ in. thick are common.

In fact, the sizes of the doors in a dwelling may be taken as a reliable indication of the general construction standards followed by the builder. If the door sizes are made to the standard dimensions noted above, one can assume that the rest of the construction follows customary standards as well. If the doors are smaller and /or thinner than the sizes mentioned above, it's likely that the builder cut corners in the rest of the construction as well. If the doors are larger and heavier than ordinary, it's a good indication that the builder tried to build a house of better than average quality.

Table 1. Standard Sizes of Wood Flush Doors: Interior Flush Doors Solid-Core; Interior / Exterior Flush Doors Hollow-Core; Flush Dwarf Doors


Door-frame Installation

There is a difference of opinion regarding just when the door frames should be installed. One group of builders will set the doorframes in place immediately after the house frame has been completed and the walls and roof installed but before the finish flooring or the plaster or wallboard are installed. A second group of builders will wait until construction of the house has been almost completed and the finish flooring has been laid down. That is, the first group considers the door- frame installation to be part of the rough carpentry, and the second group considers the doorframe installation to be part of the finish carpentry.

As far as the homeowner is concerned, the advantages to him are with the second group of builders. The point of installing the doorframes as soon as possible, from the point of view of a builder, is that the edges of the doorframes will form grounds, or straightedges, that the plasterers can use to level the plaster (see PLASTERING). This technique is certainly faster and cheaper than installing separate grounds, which are shown in Fig. 1, and the builder is assured that the doorframes (which he will have bought ready-made) and the wall finish come out exactly flush with each other, which will make it easier to install the casing.

When door frames are installed this soon, however, the danger always exists that the wood will become saturated with moisture as the plasterers and others work around it, with the consequence that the doorframe may warp as the wood dries out. (The doorframe will probably have been pre-primed by the manufacturer to minimize this danger, but the danger still exists.) The edges of the doorframe may also be nicked and gouged as the workmen move themselves, their tools, and their scaffolding about. Finally, the carpenters may leave unsightly gaps along the edge of the floor where they butt the ends of the finish flooring against the installed jambs. None of these problems can occur if the door frames are considered part of the finish trim and are installed after the rest of the house has been completed.

Doors and doorframes are widely sold as completely finished, prepackaged units, the doors being already fitted and hung within the assembled doorframe, all ready for installation in the rough opening. Doors and doorframes are also sold as complete but disassembled kits, with the jambs precut to size, the wood routed out in both jambs and door for the butts and lock, and the entire package requiring only assembly into the rough door opening.

In these prefabricated door assemblies, the doorframes are already trimmed to one of several predetermined widths. Which width the builder orders will depend on the overall interior-wall thickness, which is usually the actual width of the 2 X 4 in. stud plus 1/2 in. to 3/4 in. on each side of the stud, depending on the thicknesses of the finish wall. Plastered walls are usually 5¼ in. thick overall, and 4 3/8 gypsum wall board walls are usually 4 in. thick overall. Prefabricated doorframes are also sold in which the widths of the jambs can be adjusted slightly to accommodate the overall width of a particular wall opening.

Rough door openings are usually 3 in. higher and 2½ in. wider than the size of the doors that will be fitted into them. Before the wall is constructed, therefore, the carpenter must know what the door sizes will be, information that he will obtain from the house plans. When constructing the rough opening, the carpenter must make sure that the side studs (or bucks) and the lintel are cut from lengths of straight lumber and that this lumber is installed as plumb, level, and square as possible, otherwise the finish carpenter will have trouble installing the doorframes so they are plumb, level, and square.

It is conventional to determine the “hand” of a door, that's , the direction in which the door swings on its butts when it opens, as if one were standing outside a room looking in. Thus, for an interior door one would be standing in a corridor, while for an exterior door one would be standing outside the house. If neither of these conditions apply, then the “hand” is deter mined when the butts aren't visible from the side on which one is standing.

Therefore, when one is standing outside a house or room, if the butts are on one’s right, the door is a right-hand door, If the butts are on one’s left, the door is a left-hand door. As for the locks, if, when standing outside a house or room, the door opens away from one (the usual direction of swing), the lock is a regular bolt type. If the door opens toward one, the lock is a reverse bolt type.

Door Hanging

Doors must always be handled and stored carefully. If possible, they should never be delivered to the site until the house has been enclosed so they can be stored in a dry place. Doors should never lean against a wall in such a way that only one edge of the door is resting on the wall—the door might develop a twist. It is better for both doors and walls if the doors are laid flat until they are ready to be installed.

A well-fitted door will have a 1/16 in. clearance on top and along both sides, and a 3/8-in, to ½ in, clearance at the bottom (see Fig. 4). If carpeting is to be laid under the door, the thickness of this carpeting (plus the thickness of any pad) must be known in advance, if possible, so that the appropriate amount of space can be allowed for. If a threshold is to be installed at the bottom of the door, the final clearance need be only 1/16 in.

Fig. 4. Laying Out the door hinges and obtaining the proper fit of a door within its frame.

To fit the door, it's first wedged tightly into the doorframe in such a way that it bears solidly against the butt jamb. The carpenter then checks the clearance between the door and the lock jamb and makes whatever alterations may be necessary by planing the edge of the door. The fit between the head jamb and the top of the door is checked in the same way, the top of the door being planed, if necessary, to obtain a good fit. Finally, the fit of the butt jamb and the door is checked and this edge is planed, if necessary. Once an accurate fit has been achieved, the lock side of the door is beveled slightly with a plane to permit the inner edge of the door to clear the jamb as the door swings open. If the door were left with a perfectly square edge, this edge would scrape against the jamb every time the door opened and closed.

Butt Installation

The number and size of butts installed on any particular door will depend on the weight and size of the door. Interior doors usually have two butts installed, exterior doors have three, as do the doors leading into an unheated attic, as three butts will counteract any tendency the attic door may have to warp. The butts used for residential doors are usually of the type called loose-pin butt hinges (see Fig. 5). That is, the pin holding the two halves (or leaves) of the butt together merely drops into the knuckle, i.e., the round, central portion of the butt. If the pin is held in place by a screw located at the bottom of the knuckle, the butt is called a fast-joint butt hinge.

Fig. 5. A loose-pin type of mortise butt hinge (U.S. Bureau of Naval Personnel).

Butts may be either square-cornered or round-cornered. Round-cornered butts are installed by carpenters who have a special door-hanging template that's used with an electrically driven router. Round-cornered butts are also an indication of a prefabricated door. The square-cornered butts must be mortised in place using a hammer and chisel; they are usually an indication of better-class workmanship.

The top butt is installed first. After it has been screwed securely in place, the door is hung on it and its clearances are checked. If these are satisfactory, the door is removed from the doorframe and the bottom butts are installed. The door is then hung once again to recheck the clearances and the manner in which it swings out into the room and closes into the doorframe.

If the door clearances aren’t satisfactory, the carpenter can adjust the position of the door slightly by inserting thin strips of cardboard under one of the leaves (which shifts the door away from the butt jamb), or he can deepen the mortise slightly (which shifts the door toward the butt jamb).

If the door binds in a hinge as it swings back and forth, the carpenter will have to adjust the position (or positions) of one (or both) of the butts until the door does swing freely.

Finally, the bottom of the door is checked for clearance and for parallelism with the floor.


The two main kinds of doorstop are: (1) a strip of wood that's nailed completely around the jambs and (2) a rabbeted stop that's ploughed into the edges of the jambs. The first type is used for interior doors, the second for exterior doors (see Fig. 1). In both kinds, the stop is so located that, when the door is closed, its surface is flush with one edge of the doorframe. In both kinds of doorstop also, the stop prevents light or air passing through the edges of the door.

A variation of the nailed-on strip is a stop that rests partially within a groove ploughed into the jambs. This increases the strength of the stop, which can absorb more punishment, and it also makes the door more burglarproof, if the door is to be kept locked for any reason. With the usual nailed-on stop, all a burglar need do to open the door is force a thin metal blade between the stop and the jamb. He can in this way push the latch back until the door opens. When the stop is inserted into a groove, this is impossible.

Casing Installation

It is the casing that gives distinction to a doorway. Modern houses tend to have very simple, narrow casings, for both stylistic and economic reasons. Typically, the wood will be somewhere between 2¼ and 3½ in. wide and from ½ to ¾ in. thick. Casings intended for traditional houses are much more decorative, although there is nothing today like the heavy, ornately carved casings that surround the doors and windows in a Victorian mansion, which sometimes have spiral or fluted pilasters or half-columns set into the main molding. Nevertheless, even today a homeowner can build up an elaborate casing around the doors and windows of his home if he wants to, limited only by the amount of money he is willing to spend, his taste, and his common sense.

Basically, a casing consists of three pieces of wood—two side pieces and a top piece. Large casings are usually hollowed out at the backside of the wood. This lightens the wood, prevents warping, and it also keeps most of the wood away from the construction, especially at the gap between jamb and plaster. If the plastering should have been done unevenly, high spots or roughness in the wall that might otherwise hold the casings away from the wall are prevented from doing so, and the casing will be able to rest flush against the wall.

Casings are always set back slightly from the edges of the jambs, leaving these edges slightly exposed. Usually 3/16 to 5/16 in. of the jamb edges will show, and this dimension must be the same all around the doorframe. An uneven-looking installation is an indication of a poorly done job.

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