First, there is no standard for determining if a crack of a particular size is
not acceptable or excessive. Cracks are considered "normal cracks"
if they close during the humid season of the year. If the cracks close, the
natural wood product is simply absorbing the environmental moisture available,
expanding, and filling the gap.
To prevent unsightly normal cracks, the environment must be modified to
minimize the difference between the "Humid" and "Dry"
seasons. De-humidification above and below the flooring in the summer may be
necessary, conversely, humidification during winter heating may also be
required.
Permanent cracks may be filled with an appropriate filler and/or by
recoating the flooring. This should generally be done during the Spring or
Fall when conditions are not extreme and more average. For much of the USA,
October and April are the preferred months for remedial action.
What can I do for a Cupped floor?
1) The most common cause for cupping is excess moisture, which originates
from the subfloor, crawl space, basement, and/or slab. Excessive moisture is
usually indicated when the average moisture content of the underfloor
materials (checked in several places) is more than 4% higher than the
average expected EMC (equilibrium moisture content) for the area. (Ref.
Behavior of Flooring and Cupping & Crowning*)
If excessive moisture is the cause, identify the source, remedy the
problem, then allow the flooring to re-acclimate to the new drier
environment (this may take a heating season). After drying to normal
conditions, the flooring should flatten.
If the floor flattens with no significant cracks, movement between
pieces, or noises (crackles and squeaks) no further action may be required.
Along with the drying, shrinkage cracks, movement, and/or noises may
result. For new floors with prominent cracks, movement, and/or noises
throughout; re-installation and/or replacement may be indicated. For a floor
with the occasionally occurring larger crack (up to 3/32") , with
occasional movement and/or noise, with smaller shrinkage cracks (less than
1/32") and little or no additional movement or noises; a good choice
for repair is to:1) re-fasten the flooring in those areas which exhibit
movement and noises; 2) properly fill the cracks (fill from tongue level to
surface, filler should not simply bridge the crack); and 3) re-coat or
re-finish.
2) Cupping can also be caused by the flooring acclimating to the area or
space environment which has a higher EMC than the average moisture content
at installation. This cupping is generally permanent and changes little with
the seasons.
For permanent cupping (cupping that has not changed noticeably in 12 +
months) sanding the floor flat is the most common option, followed by
refinishing. In order to maintain the "before refinishing"
environment the same type of finish materials and number of coats should be
used. After finishing, the floor should remain flat as long as the
environment does not change from the previous norm.
For the permanently cupped floor which shows a small difference in the
cupping with the seasons (i.e. cups more during the humid season) sanding at
mid season (spring, fall) mediates the expected change.
3) For minor cupping (cupping which is not prominent and generally only
noticeable in reflected light from large windows etc) where traffic wear has
not worn the finish on the slightly raised edge, you may have to accept the
condition. Over time, 2-4 years, the cupping will probably subside.
What causes loose, squeaky, creaking, or crackling in hardwood flooring?
The cause(s) of these conditions may be singular or multiple and include one
or more of the following.
Noises and/or movement may result from:
Subfloor to support (joist) connections: i.e.; nail movement in plywood;
glue set before plywood installation; laterally moving plywood across glue
bead, etc.
Flooring to subfloor connections: i.e.; lack of nailing; lack of adequate
nailing near ends; improper fasteners such as small wire nails; where
staples are used- over driven staples, and broken tongues; etc.
Flooring match or tongue and groove fit: i.e., tongue too small for
groove or tongue too big for groove, etc.
Moisture change: i.e., too much moisture which loosens fasteners,
excessive drying which disengages flooring, system stress as moisture
tightens a floor, etc.
System specification: i.e., inadequate subfloor materials, excessive
spans or spacing, etc. Again, any one or all of the above may contribute to
a performance problem.
Remedies for floors which show movement and/or are noisy:
First, if an area of multiple strips move together in unison, a system
problem may be the indicated cause. This may require brackets to pull the
subfloor to joist from below, and/or face nailing or screwing into joists
from above.
Second, If singular strips move, a nailing/fastening or match problem may
be the indicated cause. When this condition occurs over an entire floor, if
accessible, screwing from below with drywall screws with washers to back the
head may correct the problem. If the underfloor is not accessible, general
face nailing, specifically into joists may correct the problem. As a last
resort replacement may be required.
For single strip movement in smaller specific areas (not over the entire
floor), screwing from below and/or face nailing the indicated areas, most
always remedies the movement and noise.
Third, if an excessive or high moisture condition has occurred or is
present, the cause(s) must be identified and remedied. The flooring
should then be allowed to re-acclimate to the new conditions before
other remedial repair is initiated.
