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
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
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
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
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