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Shrinkage of flooring pieces, in dry seasons, is normal
and 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 causes. Cracks in "panelized" floors
can be 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 cause a traditional joist
floor structure to stretch
across the center beam of a home, resulting in gaps between pieces
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 the raising of joist ends 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" in this case
will follow the seams of the plywood subfloor.
- Floor finish edge-bonding: Although the process is
not fully understood, apparently some types of surface finishes
such as Polyurethanes (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 joint 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 most 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 most likely
to occur along 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) a 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
gaps. 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.
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
to be 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 finish, 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. |
