DOORS
WOOD PANEL, GLAZED, HOLLOW-CORE, FRENCH & MORE: LEARNING TO READ QUALITY BY TYPE.
The familiar wood panel door is a masterpiece of available materials and technology. Found in most homes built before 1950, panel doors are designed and engineered to allow the wood to move and adapt to changes in temperature and humidity. The structure begins with a framework of vertical stiles and horizontal rails mortiseand-tenoned together. This strong framework is filled in with recessed panels that “float” between the stiles and rails. | The most traditional configuration is the frame- and-panel door, where pairs of vertical panels float over each other between rails that act as dividers.
Doors usually have between one and eight panels, and the door is often referred to by the number of panels it contains. A house built with a panel entry door usually has panel passage doors as well. Early versions of this door were cut and shaped by hand, usually by a carpenter on site. Variations to the panels—size, shape, moulding profiles, orientation—reflect different eras and styles. By the late 1800s, doors began to be mass-produced in millwork shops, at which time heights, widths, and patterns were standardized. Doors still were made from parts of solid wood, but lacked such hallmarks of hand construction as plane and saw marks.
About 1905, plywood, an assembly of thin sheets of wood bonded together with an adhesive, began to replace solid lumber in door panels. These engineered woods often were quality prod- ucts made from Douglas fir or other durable species, and the doors are worth saving today. (Only later did plywood become ubiquitous for structural uses like sheathing and subfloors.)
It’s not an exaggeration to say that plywood changed the technology of the door. It was now possible to build a door that was smooth and flush rather than a multi-planed door with four, five, or six panels. As early as the 1930s, the first flush plywood door appeared, quickly followed by the first hollow-core doors.
Pierced by slender or square geometric glass lights, flush exterior doors are a key architectural feature on many homes built in the late 1940s and 1950s. Inside, both solid and hollow-core flush doors lacking any decoration beyond hardware became standard interior passage doors.
Today, contemporary passage doors are
among the most purely engineered of building products. While the finish surfaces may look the same or similar to period doors, decades of technological innovation have changed the nonvisible parts of the door. Composite flush doors have honeycomb cores, softwood interior framing, and particleboard surface panels. The same internal technology is used for moulded doors, defined by the polymer or PVC that coats the surface. Better quality flush wood doors have a solid, continuous core of wood block or chipboard with plywood surface panels. Finish surfaces range from paint- or stain-ready to wood veneers.
Like the original engineered hollow-core doors from the mid-20th century, the quality and durability of a moulded door depends on the density, stability, and continuity of the materials that compose it. Doors made with contemporary technologies shouldn’t be rejected out of hand: these new materials and meth- ods make it possible to re-create historical patterns, especially if the door is meant to be painted. Some moulded doors cost less than $100 each, making technologically advanced doors in period profiles (like an Arts & Crafts door with five horizontal panels) a real option for renovators on a budget.
As for exterior doors, many of the patterns and styles that appeared in builders’ catalogs since the early 1900s are available in solid and engineered woods, from competing brands. They look similar to the originals thanks to innovations in veneer cladding, but the interior composition varies widely.
For example, the materials and construction methods that hold together a stock four- or six-panel door from a local builders’ supply aren’t likely to be the same as those used a century ago. Even doors billed as solid wood are often constructed with engineered stiles and rails and panels with three-ply engineered
For Flexible Joints
Traditional wood panel doors are designed to shrink and swell with changes in temperature and humidity. This makes for a longer-lived entry, but can also lead to open grain issues when bare wood at the seams and joints is exposed to the weather, weakening the integrity of the finish. The most forgiving and easily refreshed coating is stain, which should be applied on all sides of the door, including the top and bottom. Where joinery meets, saturate the seam or joint heavily with the stain before applying a finish coat—preferably a flexible alkyd exterior coating. Avoid marine varnishes or any other finish that is inflexible once it cures.
BUNGALOW DOORS: Flat trim, the horizontal orientation of a five-panel door, and a transom over a single-light door are typical of the period; this Pasadena house was built in 1910.
cores that help stabilize the surface woods. (There are even rubber “cushions” inserted in joints to help the door hold together better when slammed!)
In a good-quality door, the stiles and rails are constructed from smaller pieces of hardwood, which are clad in the desired finish veneer, usually a premium hardwood, then dowel-jointed together. (Cheaper doors are face-finished over medium density fiberboard, or MDF.) On higher-quality doors, two pieces of lumber are laminated together, front to back, to form stiles and rails. Similarly, the panels are thinner pieces of wood laminated together. Panel mouldings (aka “sticking”) are sometimes made of solid lumber and applied to rather than cut into the panel.
A step up, grade-wise, are doors with solid wood rails cut from one piece of lumber, with matching grain patterns on both sides of the door. Only the most expensive manufactured doors have mortise-and-tenon joints. Ironically, these extrasturdy joints are sometimes reserved for doors made with engineered cores.
For wood doors made the tried-and-true traditional way, look for smaller companies that specialize in re-creations of historic doors. Vintage Doors, for instance, makes its doors from furniture-quality woods including poplar, cherry, and Honduran mahogany. The doors are built with real stiles and rails, and are fitted together with cope-and-stick construction, using a joint where one moulding is cut to mate with the profile of the second.