Wood door restoration, repair and refinishing


Restoration may be less expensive than replacement

Doors fail in many ways; rot damage, weather damage and sunlight damage are usually repairable.
By using high-quality products and simple procedures, long-lasting repairs can be done.

Doors made of wood are the door of choice on homes. The reasons include simplicity, cost and beauty. Unfortunately, they are not always well-made, may be distributed to the public by large chains that buy from the lowest bidder, and may have poor-quality clear finishes on them. The home-owner or apartment-manager may buy an unfinished door and then whatever clear finish some store sells, expecting that it all will last for years and years, as did the “Factory-applied” finishes of their youth. The modern over-the-counter finishes are mostly waterborne, mostly fail sooner, and even the wood itself is much lower-quality than the wood of houses in which we grew up. The decay of our buildings continues, and at a faster rate. More effective technology is needed to make things last.

This technical note addresses the main reasons wood doors fail, and how to deal with those failures. It is based on over thirty-five years of study of the failures and application of effective technology by hundreds of thousands of people all over the world.

The main sources of failure of wood doors are from wood rot, from weather damage (meaning water and temperature) and from sunlight (part of weather, but it needs special treatment).

Failure due to wood rot is dealt with (assuming the rot is not TOO bad) by Restoration. The Modern Technology That Restores Deteriorated Wood was invented by myself in 1972 with the invention of Clear Penetrating Epoxy Sealer™. This is also discussed Smith & Co. website, on the page The World’s Greatest Primer. Much more detailed information about the underlying science is in a paper by myself, one of my staff scientists and an architect.

The general topic of Restoration of Wood is discussed in an application note of that name, part of the Smith & co. literature package included with those products. It is a very general application note. For the particular case of restoration of a wood door due to rot damage, there are some additional guidelines:

Rot damage is usually found on the bottom edge of a door. Sometimes on the top, but usually only the bottom. This is because storm-water usually runs a bit under the bottom edge and may not fully drain, thus it is a damp environment. Finishes are not usually well-applied to the bottom edge of a door, since it is not visible. Thus, doors painted new or repainted tend not to have a decent protective coating on the bottom edge, and what may be there often fails and is not visible, thus the coating failures go unseen; rot begins, continues for years to eat away the underside of the door, yet the outer surface looks fine, and who notices the bottom quarter-inch of the outside of their front door, anyway? By the time some warping of the outer surface and coating failure is visible, rot damage may have eaten an inch or three into the bottom edge of the door.

The first step is removal of the completely deteriorated part. It is VERY difficult to do a good job of this without taking the door off its hinges, since one needs to probe the depth of decay with an icepick to assess how much material needs to be removed.

Doors often have a wood veneer laid over a solid wood core similar to a rail-and-stile frame, and it may be that the veneer and some of the adjacent wood is intact, with the rot extending mainly up into the end-grain of the vertical pieces called stiles (the horizontal pieces of a panel door are called rails, see for example this page.

In rail-and-stile panel doors, it again is usually the porous end grain of the stiles that is deteriorated, and usually deepest in the middle.

Try to excavate only the central part of the deteriorated area, leaving the external door surfaces intact. They will be stabilized with the first-step impregnation of Clear Penetrating Epoxy Sealer, and leaving the outer surfaces intact creates a reservoir. When you stand the door upside down and pour the Clear Penetrating Epoxy Sealer into that cavity, it will wick directly down into all the deteriorated areas of the wood. Keep the reservoir filled, so all the wood gets impregnated. After about ten minutes, what remains in the cavity can be removed with such as a turkey baster. Now, some time needs to be allowed for the solvents to evaporate. If you are working indoors in the shade and using the Cold Weather Formula of Clear Penetrating Epoxy Sealer, lower the door so it is resting on its long edge and arrange a fan blowing air directly into the cavity, to give good ventilation and help the solvents to escape. A couple days is usually adequate for that step. Next, the Fill-It Epoxy Filler is applied, and at this point we are back to the general directions of Restoration Of Wood as mentioned earlier.

Failure due to weather damage (meaning water and temperature) is dealt with by addressing the damage. Usually this is a lifted finish, either paint or some clear finish, and some cracking of the wood, often with decay behind. The wood is usually discolored. If the door is to be painted, discolored wood does not matter. If it is to be clear, it may be best to stabilize the wood with the Clear Penetrating Epoxy Sealer, and then sand and stain. Directions for staining wood are in the application note Staining Wood.

An old, failed finish needs to be removed. Sanding or heat-gun-and-scraping are the recommended methods. Some chemical strippers can leave a residue in the wood that will interfere with adhesion of the coatings, or may act as a paint-remover within the wood, and months later some of the finish may soften and blister.

There may be cracks in the weather-damaged area. Cracks in wood may be called checks. They are dealt with by first, application of the Clear Penetrating Epoxy Sealer and second, by filling with the Fill-It Epoxy Filler. A final sanding and then priming of the area with Clear Penetrating Epoxy Sealer, and we are ready for the finish application.

Adhesion of the finish is important. The finish is there to protect the wood from weather and water damage. If the finish fails, then the wood underneath begins to fail. The purpose of the Clear Penetrating Epoxy Sealer is to glue the wood fibers together below the surface, to seal the porosity at the surface, and to glue the finish to the wood, thus protecting everything underneath. High quality doors are made this way at the factory. Low-quality ones are not, and then repairs must be done years later.

Failure from sunlight is addressed by removing the degraded and failing finish and applying a better one. It is normally clear finishes that fail from sunlight, due to the various attack mechanisms. A pigmented finish (paint) normally fails on wood when the coating is too stiff, the normal expansion of the wood cracks it and allows water to get in, the water cannot easily evaporate out the crack, warm damp wood allows rot fungi to eat the wood under the paint, and then the paint comes loose from the wood, cracking and peeling. Refinishing of doors is also discussed in a City-Data posting.

Those are the main failure mechanisms for wood doors, and the links above give the refinishing procedures. For more specific information you may email or telephone Smith & Co. at 1-800-234-0330.

© copyright 1972 - 2009, The Brain Trust, a California irrevocable trust,
reprinted with permission