 
"Panelizing"
of In-Place 3/4 Inch Hardwood Nail-Installed Floors
CAUSES & CURES
Description:
An un-natural behavior pattern of
installed strip or plank flooring due to causes which occur naturally can be
aptly described as "Panelizing". This appearance can
develop during the first or even subsequent heating seasons. It is caused by
flooring boards throwing off moisture and shrinking in random groups. The
groups, or "panels" may be any random number of boards. Within this
"panel" boards remain tight together. This transfers the aggregate
shrinkage -- that is the total shrinkage for all the boards in the panel -- into
large cracks on either side of the "panel".
Shrinkage of and by itself, in dry seasons, is not at all unnatural.
Normally, however, shrinkage is manifested in hairline cracks beside each
individual board or strip. When floors shrink in panels, the movement is not
natural, and has some underlying cause. Cracks in "panelized" floors
are almost always very noticeable and objectionable, and sometimes require
professional attention.
Causes:
On a job site many external forces act on
a hardwood floor, tugging, pushing and locking strips together. It is the
external forces that create a panelized floor. No manufacturing or kiln drying
procedure (nor lack of one) during production of the flooring itself can produce
this phenomenon.
Some causes more commonly found behind "Panelizing":
Foundation settlement: Perimeter foundation settlement can literally cause a
traditional joist floor structure to stretch across the center beam of a home,
resulting in cracks in surface floors. If the settlement is extreme, a
"jack-knifing" effect in the joists may also result. In this instance,
humps will be formed in the floor, caused by raised ends of joists near the
center beam. (In a strictly technical sense, this effect is not
"Panelizing" but just large abnormal cracks.)
Cracks or "panels" caused by foundation settlement usually occur near the
center beam, and often are limited to one or two major cracks. They can occur
elsewhere, however, particularly when plywood is the subfloor "panels" will in
this case follow the subfloor seams.
 | Floor finish edge-bonding: Although the process is not fully understood,
apparently some types of Polyurethane (and perhaps other ) floor finishes seep
between flooring strips, and when dry literally glue the boards together. When
flooring so affected begins to lose moisture in--dry (heating) seasons, the
floor shrinks and joints break apart only at the weakest points. These can occur
randomly or in a repeat pattern, but because all the shrinkage of the boards in
the panel occurs at these "panel edges': the "Panelizing" effect takes place.
Makers of floor finishes are undecided as to the exact cause, but floor
finishing mechanics are advised to employ the total system specified by the
finish makers, as skipping a required sealer coat may at times contribute to a
Panelizing effect.
| Subfloor movement: Subfloor material very often must remain exposed to the
elements for days or weeks while the building is under construction. Any
subfloor material suitable for nail-installed hardwood flooring will take on
excess moisture from exposure to rain or high humidity, and will begin to throw
it off as soon as the environment is favorable. When this occurs, the subfloor
material, joists, beams, and every wood component with a higher moisture
content, will shrink. Subfloor shrinkage, or shifts caused by framing movement,
can cause surface floors to develop cracks. These may appear in any sort of
random pattern, including "Panelizing".
"Panelizing" is more often caused, in the case of subfloor
shrinkage, by movement of subfloor panels (4' x 8' plywood, for instance).
Plywood has been shown to retain fasteners well, and when cycled through normal
seasonal moisture changes, holds flooring strips tight to the plywood surface.
As both the plywood and flooring dry, the plywood tends to pull expanded and
re-dried flooring strips back to their original position on the plywood surface.
This characteristic sometimes produces a "panel" effect in the surface hardwood
flooring, with separations roughly corresponding to edges of plywood panels.
This is more likely to occur when the long dimension of plywood panels parallel
the direction of flooring strips.
Cures:
The remedy often demanded by unhappy
owners, is to remove and replace "panelized" floors with new flooring
material. However, this is usually not the best cure, because if the cause for
"Panelizing" is still there or repeated, it will happen again with the
new floor.
Also, once hardwood flooring has settled-in to its environment, particularly
after going through a typical new-home moisture surge (i.e. moisture trapped
inside during construction) and drying period, it is less likely to misbehave
than would a new floor brought in from a different moisture environment.
Whenever possible, it is advisable to repair the existing floor and re-coat or
refinish as necessary. In a settled moisture environment, the existing hardwood
floor is the best choice for future trouble-free service and is less trouble for
the occupants, as it has already acclimated.
The cure for Panelizing is, of course, to remove or repair the cracks. A
number of options are available and any or all may be required on the same
floor. Some of these are:
 | Removal and replacement of selected boards: Where large "panelized" cracks
occur near a wall or other vertical obstruction, those boards nearest the wall
can sometimes be removed and reinstalled to eliminate the cracks. Where
possible, replace the same boards removed, in the same sequence. This will allow
simpler finish repairs.
| Filling Cracks: By using filler made from sanding dust from the same or
another floor mixed into a paste with either-
A.) The same stain or pigment used to color the floor originally or...
B.)
A surface finish without coloring, if the floor is finished natural.
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If performed by a finisher, a commercially prepared filler is
also suitable, if properly colored to match the floor. Filling should be
performed when the moisture content of the flooring is at its median stage,
halfway between its highest and lowest seasonal readings. Typically, in
four-seasonal areas, this will occur in late spring or fall. Every year the
flooring will expand with moisture gain and shrink with loss of moisture, so the
trick is to fill the cracks when the filler line will be small enough not to be
squeezed out as the floor expands, but large enough to leave the smallest
possible crack in dry seasons.
If cracks are near 1/8" and wider, filler will be squeezed out as the
flooring expands in humid seasons, or the filler itself may break with chunks of
filler vacuumed away, leaving a jagged crack.
In all cases, repairs should be performed by an experienced floor
finisher whose judgment should be relied on to provide the proper remedy for
each circumstance. Experience is the best teacher in deciding which cracks will
hold filler, which need boards relocated, (or wider boards custom fit to replace
cracks), and how best to match the filler to the surface.
If only filling has been necessary, and if the floor has a Polyurethane
coating or seal-and-wax finish, the finish can normally be repaired very simply
after the filler is well dried. First, buff the floor with a NO 120 or finer
screen, and clean thoroughly (vacuum, tack). Then re-coat with one coat of
Polyurethane, or, in the case of seal-and-wax, re-wax with colored wax to match
the original.
White-finished floors offer some potential problems due to the nature of the
pigmented coloring, and where it lies within the finish. The above technique can
be tried, and if results are unsatisfactory, full refinishing may be indicated.
If boards are replaced with new, un-sanded stock, it will probably be
necessary to re-sand and re-finish the entire floor.
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