Interior doors are moveable structures designed and constructed for indoor use. The primary function provides access and egress to a room or other space inside of a building. These doors are used in residential and commercial applications to:

• Provide privacy
• Help reduce noise from other parts of the building
• Separate one interior space from another
• Aid in ventilation
• Let in light

The exact time in history interior doors were first introduced is unknown. The earliest record of their use was discovered in ancient Egyptian tombs. Archeologists have documented the existence of wooden doors inside individual tombs. Beyond these first discoveries, ruins of ancient Greek and Roman interior entryways reveal the popularity of interior door use. While functionality was necessary, the interest increased due to interest in style as well. The Greeks and Romans built single, double, sliding, folding and even automatic doors out of wood, stone, metal and a combination of each. While interior doors in the post-industrial era have become commonplace, they are still valued for many of the same reasons.

Types

Commercial doors are built to a higher level of durability in order to withstand heavy traffic and repetitive use. Additional structural requirements must be met to comply with building codes, fire protection and access for the handicapped. However, the types of doors available for commercial and residential applications do not vary. Types include:

• Passage doors, most common in homes, swing open and close shut via leaf hinges. Available as a slab door, which is a single unfitted panel, or otherwise prepared for installation in a doorway or pre-hung
• Accordion doors that hang suspended from the top and slide horizontally to open and close
• Dutch doors that are similar to passage doors and have been cut in half along a horizontal line, creating a lower portion and upper portion of the door that opens and closes independently
• French doors. A combination of two doors that function as one by meeting at the center while hinged opposite one to another
• Sliding doors that have one panel or more and move along a horizontal track to help utilize space efficiently
• Bifold doors have a fixed end and one or more pivot points between panels to provide large openings and save space
• Bypass doors are two single doors that meet in the middle and overlap when slid horizontally
• Pocket doors that slide open and shut on a horizontal track running into a pocket in the wall
• Flush doors, which have a flat or flush hardwood surface
• Mirror doors that contain full-size mirrors or partial mirror covers on at least one side

• Shower doors that prevent water from escaping and are hung to enclose a shower

Operation

All variations of interior doors operate with hinges, tracks or a combination of both. Hinges are positioned for adequate swing motion while tracks enable doors to slide. Bifold doors use both horizontal tracks and hinges. Panels utilize hinges to fold in or out as the full door rolls open or shut along the track. While horizontal tracks are the most common, some interior doors open and close on vertical tracks when pushed up or pulled down.

Features

Interior doors have an assortment of safety features including fire resistant or fireproof, blast resistant and bullet resistant. Optional windows create visibility between rooms and open a space visually. Insulated doors deliver thermal insulation for higher energy efficiency and serve to reduce outside noise.

Each type of interior door is designed with unique features in mind. For example, sliding and bifold doors use tracks that maximize space in smaller areas. Dutch doors are made with lower and upper halves that open and close independently.

Numerous interior doors, particularly residential varieties, have distinctive core options for each type. Hollow-core doors with a veneer facing the outside have a cardboard base, making them lightweight and inexpensive. Solid-core doors feel and look like solid wood doors that yield similar levels of soundproofing and durability, yet have a wood fiber core.

Applications

Interior doors exist in residential, commercial and industrial applications. The most frequent application is to provide a barrier that allows access and egress between rooms. Interior doors are also used to enclose showers, closets, cupboards and other specialty interior spaces.

Materials

Materials used to make interior doors are selected based on their intended use and necessary function. These factors include security necessities, durability, a degree of fire protection, desired visibility and esthetic tastes. A single material or a combination of materials include:

• Wood
• Plastic
• Aluminum
• Stainless steel or steel
• Copper
• Bronze
• Precious metals
• Glass

• Fiberglass

Selecting Interior Doors

Residential interior doors have a wider selection of designs, shapes, sizes and esthetics due to the emphasis placed on these characteristics by consumers. The consumer profile is that of homeowners, landlords and property owners and online research is a primary starting place during the selection process. Commercial and Industrial interior doors have a more specific selection criteria, and suppliers have less web presence than residential product resellers. For buyers of these products, a web search to find suppliers and manufacturers is an excellent first step. However, detailed product information, images and user reviews are scarce. Therefore, direct contact with these suppliers is a must.

During the selection process, several factors are essential to making the best choice. The height and width must coincide with the installation area to ensure a proper fit. Other aspects include:

• The importance of blocking or reducing noise
• Durability and strength requirements
• Absorption of substantial impact
• The space available on either side of the doorway

For commercial and industrial doors, meeting more stringent building code requirements like fire protection and safe egress and accessibility for the handicapped are critical details during the selection process.

Standards

ASTM F821/F821M - Standard specification for domestic use doors and frames, steel, interior, marine

References

Image Credits:

General Door & Locksmith

Midwest Doors & Interiors

Grainger Industrial Supply