Water damage to wood floors

John Horton <jhorton [at] ncsl__dcr__state__nc__us> writes

>I
>am requesting information from anyone on the Conservation List who
>has had any experience with the restoration of water damaged
>flooring, i.e., cupping, buckling.

To correct the distortion caused by excessive amounts of water to a
wood floor can be a very time consuming endeavor, To save the paint
layers complicates matters even more. It is helpful to have
experience in wood bending/drying dynamics, wood species knowledge
and coatings consolidation. I have never removed warping from a
floor, my experience being primarily with furniture, given the right
methodology and enough time, I believe it can be done.

One must remember that dry wood fibers have a memory of shape and
relative position to each other. When a board gets wet and dries,
any distortion is fixed and any paint is no longer firmly bound to
its substrate. Also, once dry, its probability of being permanently
shrunk in width is almost assured. A Poly(ethylene glycol) PEG
solution may help to eliminate some shrinkage and distortion but may
also negatively effect reattachment of the paint layer.The cost of
materials and time may also out weigh any gain PEG can offer.
Preferable treatment would be done before the board has dried from
the damaging water, but this is almost never the case. As years go
by the memory of distortion is reinforced.

The number of growth rings per inch and grade of lumber determine
the rate of shrinkage. Vertical grain offers less shrinkage and
cupping is easier to correct. Flat grained boards are more
susceptible to shrinkage and cupping more difficult to correct. When
one bends wood, the greater degree of upset or radius achieved the
less spring back when dry. Cupped wood can be considered a mild
upset. To correct cupping, moisture needs to be introduced into the
convex side allowing minimal diffusion to the concave side. Fiber
saturation should not be reached out of concern for the paint layer.
After swelling the board begins to flatten. Also, if the paint layer
were not a concern, I would add some steam (even though pine has a
low content of lignin) at this point to help prevent spring back.
Hot steam, a plasticizer can dissipate a lot of internal stress.
Sometimes, especially with flat grained boards, after the treatment
moisture has dried one can reintroduce moisture a second time. This
rewetting reinforces better memory by relieving retained stress but
is not essential if steam is used. After the introduction of
moisture the board needs to be clamped flat and held until dry. The
ideal environment for drying is a room or building with good
ventilating conditions, where the moisture can gently decrease and
temperature remain relatively constant at 70 to 75 degrees F. Using
fans to force air directly over the boards will result in rapid and
uneven drying which can cause splitting or distortion. The longer
the board (wood without a paint layer) remains clamped and stickered
or in a press (wood with a paint layer) the more certain the cells
will remain stress free when returned to the floor. The length of
time can be weeks, months or longer if the cupping is stubborn or
very old. In this case one may need an additional recycling of
moisture.

What about the loose and flaking paint? The clamping/ pressure puts
the fragile paint bond at further risk and more flaking can occur.
The use of Tyvek can aid as a mechanical cushion to reduce abrasion
and control the release of moisture. The process of readhering the
paint is no easy task so testing must be done. Ideally, the
consolidant would be a water-based system since water is used to
treat cupped wood. The use of Aquasol for consolidating the paint
layer has possibilities. If under the paint layer, the boards were
originally heavily coated with shellac, then a slow drying alcohol
can be tried after the board is removed from the drying press.
Consolidating the coating is implemented only to save historic
fabric and not intended to return the coating to a serviceable
state. Due to the large quantity of boards, ease of treatment, time
duration and durability, one might want to consider not saving the
paint layer.

To treat the floorboards in place as a floor would be a rather
complicated endeavor, but not impossible. The easiest way would be
to remove each board by cutting the nail in half between the board
and joist. Once treatment is completed, return each board to their
identified positions on the joists (using original nailing holes?).
The shrinkage problem is solved by an addition of a "new" last
board. Finally, correct any for aesthetic or protective
discrepancies concerning the paint layer.

I have not found much written on this subject. Some related
information can be found in the kiln drying and steam bending
literature. Contact me if you have questions.

John Kjelland, Conservator
Missoula, Montana

                                  ***
                  Conservation DistList Instance 12:26
                Distributed: Tuesday, September 15, 1998
                       Message Id: cdl-12-26-001
                                  ***