Because doors are highly visible, hardworking parts in a home's interior, they deserve thoughtful attention when it comes time to buy new ones. The right doors will stand up durably to daily usage, minimize sound transfer between rooms, and add character or style to the home's overall interior design.

Interior doors come in two basic types: flush and panel.

Flush doors have flat, smooth surfaces that are typically painted or stained with wood stains. They are basically nondescript and, as a result, blend in with a home's interior (unless that interior is quite traditional or classic). Hollow-core flush doors, installed in millions of homes for the past 50 years, are lightweight, low-cost versions of the flush door. These have an inner softwood frame surrounding cardboard honeycomb cores, and are faced with thin wood veneers. They are damaged relatively easily and allow considerable sound transfer. Those surfaced with lauan mahogany veneer have particularly soft surfaces that do not receive finishes very well. Surface veneers of birch or other hardwoods are stronger and take stain or paint better.

Panel doors are made from a framework of horizontal rails and vertical stiles that frame flat or raised wood panels or, in some cases, glass panes. This construction method is common for solid-wood doors because it minimizes the effects of wood's tendency to shrink, warp, and swell with variations in humidity. The best types are built with precisely fitted, interlocking sections, and they are significantly more expensive than flush doors. A good, less expensive alternative with much the same look as a wood door is a medium-density fiberboard (MDF) door. This type is solid and won't swell or bind. In addition, it takes a finish well. Although new wood doors are sold unfinished and must be stained or painted, MDF doors come primed and ready to be painted.

Door Sizes
 
Standard interior doors are 1 3/8 inches thick and 6 feet 8 inches tall. You can special order taller doors but, if you do, be prepared to pay a premium. Standard interior door widths run from 24 inches wide (used for closets and small bathrooms) up to 36 inches. A door that is 36 inches wide is necessary for handicap accessibility. If you're planning new doorways, be aware that many furniture pieces are too large to pass through doorways that are less than 30 inches wide.

Pre-hung Doors and Blanks

Interior doors are sold pre-hung in frames or as doors only, called blanks or slabs. The latter type are for hanging in existing door frames or for mounting in a situation where the interior carpenter is up for the challenge of building the entire jamb set. They are sold without hinges, knobs, or locksets, but they may be ordered with a hole pre-bored for the lockset.

Pre-hung doors are the preferred choice in most situations because of the labor they save. The door comes mounted to a jamb set, with hinges mortised into the edges. When ordering this type, you specify the surface-to-surface thickness of the wall and the size and location of the holes for the lockset.

Understanding "Left Hand" or "Right Hand" Doors

A door that opens toward you and has its knob on the left side is a left-hand door. A door that opens toward you and has its knob on the right side is a right-hand door. --DV