Wood doors provide functionality, beauty, style and have maintained their popularity despite the rise of other door material types of the late 20th century.
There are two primary types of wood doors:
Panel with Sash (pane or sunburst)
French - Nearly Fully Glazed
French Door w/ multiple divided lites
Originally wood doors were primarily of the ‘plank’ variety which often gave way to moisture expansion/contraction. More currently, the two primary styles of doors are ‘flush’ and ‘stile-and-rail’.
Stile and rail doors when introduced were touted for their sophisticated look and resistance to moisture expansion/contraction. These stiles and rails essentially ‘float’ in unglued grooves allowing minor movement. Stile and rail doors may be solid softwood or veneered hardwood.
The joints are typically doweled and dovetailed with mortises and tenons.
While stile and rail doors are still popular, more recently ‘flush’ doors have captured the market due to ease of manufacturing giving way to an economical advantage.
Solid core doors commonly comprised of bonded lumber blocks (most economical), particle board, or mineral composite (fiber core). They are most commonly available in thicknesses of: 1-1/8″, 1-1/4″ fiber core; 1-1/4″ through 2-1/2″ wood block core. 1′-6″ through 3′-6″ widths in 2″ increments are most common with 5′ maximum, and 6′, 6′-6″, 6′-8″, and 7′ heigths most common, with 12′ maximum for lumber block core. Fiber core doors are available in 6′-8″, 7′, and 8′ heights most commonly, but this can vary by manufacturer. Solid core doors are used most commonly for exterior doors but are also popular anywhere sound insulation, dimensional stability, or fire resistance is desired.
Hollow Core doors have interlocking wood grid strips, ladder strips, spiral blanks, or corrugated honeycomb. Typical thicknesses consist of 1-1/8″,1-1/4″, 1-3/8″, 1-3/4″, widths from 1′ to 4′ in 2″ increments, and heights of 6′, 6′-6″, 6′-8″, 6′-10″, and 7′ or more.
Hollowcore doors have a framed stile and rail system on the inside of honeycomb corrugated fiberboard or interlocking horizontal/vertical wood strips. They are relatively lightweight but have fairly poor thermal or acoustic insulation value. Hollow core doors are rarely used as exterior doors unless they are bonded with waterproofing adhesives.
Since the vast majority of doors are not solid wood, they are faced with single or multiple plies of thin wood veneers, referred as banding (vertical grain), cross banding (horizontal grain), and face panel. The 3 primary hardwood veneer grades are premium, good, and sound.
Premium grade veneers are most conducive to natural, transparent finishes. Good grade veneers are most conducive to transparent or paint finishes. Lastly, sound grade veneers are for paint finish only and will typically require two coats. Other faceboard panels available which can be painted are hardboard. Also, high pressure laminate may be bonded to the face panels.
B’Rated doors have a 1 to 1-1/2 hour fire rating. C-Rated doors have a 3/4 hour fire rating.
Premium grade birch and red oak are the standard level quality door, with many other types available.
Cost of doors vary based on the wood quality and type. Doors may be prefinished at the factory or finished on the job. Prefinished doors often will require minor touch ups on the job due to knicks, dings, and scuffs. Below is a chart showing an approximation in cost in relation to a value of premium grade birch and premium grade red oak being at a constant index factor of 1:
In commercial construction, flush doors are commonly solid core. Also wood doors can be produced with a fire-resistant mineral core which can qualify them as ‘fire’ doors. Wood flush doors are typically grouped into 3 categories; Standard Duty; Heavy Duty; and Extra Heavy Duty. A flush door may have glass inserts or louvered inserts but such openings shouldn’t be more than 40% of the door area. Inside flush hollow core doors are Rails (horizontal top & bottom), lock rail (horizontal center), stiles (vertical jambs), and lock blocks (vertical near center).