ebuild Guide to Interior Door Specifications

Finish carpentry details can have a dramatic impact on the appearance of a house interior, but few have as much visual and functional impact as an interior door. A typical two-story house can easily have 18 or more interior doors of various configurations, and most of them are used regularly. Homeowners often focus their praise on doors they find appealing, or their ire on doors that operate poorly or don't match the style of the house. Interior doors come in a wide variety of woods, construction types, sizes and formats. In the broadest terms, they can be categorized either as panel doors or flush doors.

Panel doors--A panel door consists of stiles (vertical side pieces) and rails (horizontal pieces) made from solid wood. The spaces between stiles and rails are filled with loose-fitting panels made of solid wood or plywood. The panels fit into grooves in the door stiles and rails.

Flush Doors--A flush door features front and back surfaces that are largely flat. A further distinction comes with the construction method. Hollow-core construction consists of a honeycomb-like structure surrounded by a band of solid wood; both faces of the door are covered with veneer, hardboard or thin plywood. The doors are light in weight but are not as durable as solid-core flush doors, which are solid panels of laminated wood, MDF, HDF, or particleboard, covered with wood veneer. Solid-core construction is sometimes specified to reduce noise transmission, as between a bathroom and a hallway. Flush doors usually have surface veneers of birch, oak, or mahogany.

This distinction between flush and panel doors was originally based on a fundamental difference in how doors were constructed as well as their appearance. However, recent innovations in materials and manufacturing techniques have made it more difficult to distinguish between the two types purely on their looks. A number of manufacturers, for example, offer flush door construction with the traditional detailing of panel doors.

In terms of cost, there's some overlap between high-end flush doors and the lower end of the panel door range. This is particularly true when it comes to molded high-density fiberboard doors, which feature crisp surface details similar to those of panel doors and a texture that resembling hardwood.

Key Specifications

Size type--Doors come in a range of standard (stock) heights and widths, but are commonly 1-3/8-inches thick. Custom or special-order doors may be available at significantly higher cost.

Nominal dimensions--The nominal width and height of a door refer to the dimensions of the door itself, not including the frame. They are given in feet and inches, or as inches only (for example, height may be noted as 6'-8" or as 80"). If a door must fit into an opening of some unusual size, most remodelers order the next size up and then trim the door to fit. The alternative is to order a custom door.

Wood species--With flush doors, wood species generally refers only to the surface veneer and is primarily a matter of aesthetics. With panel doors, however, it refers to the entire construction of the door. In that case, the species determines how dimensionally stable the door will be as well as its appearance, and it has a significant impact on cost. Pine is often specified for paint-grade panel doors, while luaun mahogany is a common surface for paint-grade flush doors.

Color/Finish--Doors that will be painted or stained on site are typically delivered unfinished. A factory-applied primer coat is an option for doors that will be painted, and makes the door more resistant to expansion caused by moisture picked up in transit or on the jobsite. Doors are also available with a factory-applied final finish, though the color range may be limited.

Panel style --This is primarily an issue for solid wood panel doors, though some molded solid-core flush doors may also be described by this feature. Panels that are thicker at the center than at the edges are called raised panels, while those with a consistent thickness are called flat panels. Flat panels are typically less expensive than raised panels.

Panel shape--Most panels are square or rectangular, but the uppermost panels in a door sometimes feature a shallow arch shape called an eyebrow or a more rounded shape called a radius.

Lites--Lites are made of shatter-resistant glass and can replace wood panels. Consider this option where light transmission is important and privacy isn't required, as is often the case with French doors.

Top profile--Most doors have a square top. Arched-top, angle-top and other non-standard-shaped doors are available but may require special ordering.

The specifications above apply to the door itself, but hardware is another factor to consider. All doors require some sort of mounting hardware, such as hinges, pivots, or tracks. In many cases the hardware will be supplied with the door, but in the case of slab passage doors, it must be purchased separately. The type of metal and its finish affect how the hardware looks as well as its durability and cost.

Doors for various applications

Passage Doors--Passage doors swing open and close on two or more leaf hinges, and are the most common doors in most houses. They can be purchased either as a slab (just the door itself) or as a pre-hung unit. A prehung door comes pre-installed within a door frame, with hinges already attached and the door itself usually bored for a lockset. Pre-hung doors save installation time by eliminating the need for a carpenter to construct the jambs, mortise the hinge gains, and fit the door to the jambs. However, the choice of hinge style and configuration is limited. Pre-hung doors include two side jambs, a head jamb, and stop moldings that the door closes against. One-piece jambs are available in standard widths for plaster and drywall construction. Two- and three-piece adjustable jambs are also available for use with unusual wall thicknesses.

Louver Doors--Louver doors are essentially standard passage doors in which all or some of the panels have been replaced by angled wood slats. Louver doors are typically used for closets and laundry rooms because they provide ventilation as well as privacy. A full-louver panel format offers the most ventilation, but a louver-over-panel format makes the door appear similar to solid panel doors in the house.

Sliding Doors--Sliding doors sometimes called a bypass doors, are typically specified for use on unusually wide openings. They don't swing open so they won't interfere with furniture placement, making them particularly popular for use on bedroom closets. Access to the closet is obtained by sliding the doors right or left, but only half of the opening is accessible at one time. The door track is attached to the underside of the head jamb and can be hidden from view with a piece of trim. Sliding doors are guided at the bottom by a small piece of hardware screwed into the floor where the doors overlap. The exterior surface of sliding doors is sometimes covered with a shatter-resistant mirror.

Bifold Doors--Bifold doors are often used to enclose a closet, pantry, or laundry area. The doors may be wood, metal, or a composite such as wood covered with vinyl. Unlike sliding doors, bifold doors can be opened so nearly the entire opening is exposed at one time. Each individually-hinged portion of the door is called a panel, and a typical door has 4 panels. However, the tracks may be cut in half if only two panels are necessary. Bifold doors pivot on pins inserted in their top and bottom edges. The pins fit into adjustable metal sockets in the tracks and can be raised or lowered to fine-tune the fit of the door.

Folding Doors--Sometimes called accordion-fold doors, folding doors are made from wood, reinforced vinyl, or plastic-coated wood and take up little space when opened. A folding door may be used as a room divider or to close off a laundry area, closet, or storage area. Folding doors hang on nylon rollers that glide in a metal track that can be concealed with matching wood molding.

Mirror Doors--Flush passage doors with an inset of shatter-resistant mirror glass are popular options for bedroom closet doors. However, a mirror door can also be suitable for bathrooms. Some manufacturers offer doors with a mirror on one side and a raised panel design on the other.

French Doors-- These paired doors often provide a dramatic focal point in a house. They hang on hinges located at each side of a wide door opening and swing toward each other, meeting at the center. When both sides of the door are open, the area between the jambs is unobstructed. French doors are usually fully glazed; come in a variety of divided lite patterns and can be mounted to swing either into a room or away from it.

Pocket Doors--Pocket doors slide into an opening or pocket inside a wall. They are particularly convenient where there isn't enough clearance for a passage door to swing. Any door style or format with a thickness of 1-3/8-inches can be installed in the pocket, making it possible to match other doors in the home. However, upgraded hardware is required when the door itself is unusually heavy. Carpenters should consult manufacturer's installation instructions before they frame the wall in which the pocket door will be housed.

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