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Stop "Gap" Measures
Overzealous acclimation leads to an
unacceptable floor
by
Mike Harde
Northeast Floor Covering Inspection
& Consulting Services.
The Problem
Last January I inspected a wood
floor in a New England residence.
The 3.4-by-3-inch solid,
factory-finished white oak floor had
gaps between the boards.
The Procedure
The wood floor was in a new,
single-story woodframe home with a
full basement. The flooring was
delivered (with an average moisture
content [MC] of 8.5 percent) to the
site in July and then acclimated for
three weeks in the living room (at
the time, there was no climate
control operating in the house).
Before installation, the MC of the
flooring was checked and was at 10
percent, showing acclimation to the
environment. The subfloor at the
time was at 11 percent MC, and the
framing was at 12 percent MC. The
floor was installed by mid- August,
the residence was occupied and the
HVAC system turned on. Following
installation, the floor developed
gaps between the sides of the
boards. Gaps were minimal at first,
but by the time of the inspection
they had become noticeable,
averaging 0.040 inch. The
environmental conditions in the home
during the inspection were
appropriate for performance of a
wood floor. Flooring readings
measured 6 percent MC, with the
indoor environment at 31 percent
relative humidity (RH) and 67
degrees Fahrenheit (humidification
was in place and functioning).
The Cause
The wood flooring
lost moisture during the seasonal
dry period and developed gaps.
However, “seasonal gaps” are just
that: seasonal. They close during
periods when the flooring gains
adequate moisture. In this case,
once the home was occupied, the
home’s environment was maintained
between 30 and 50 percent RH
year-round. This wood floor is
unlikely to be in conditions again
where humidity will reach levels
necessary for the gaps to close
entirely (in excess of 60 percent RH
for a MC of 10 percent). These gaps
are not
seasonal. There will
always
be gaps in this
floor, and when the interior
environment is at the low end of its
seasonal humidity range, the gaps
will be prominent. The 10 percent MC
of the wood at the time of
installation will never again be
reached as long as the homeowners
use the year-round climate controls.
How to Fix the Floor
There is no way to restore the
flooring to a closed, gap-free
condition other than to maintain
overly high humidity levels during
the drier periods of the year, which
is impractical and can even be
unhealthy. In this instance, the
flooring was removed and replaced.
In the Future
It’s critical to identify the
expected year-round interior
environmental conditions and account
for them prior to installing the
flooring. This requires looking
beyond the MC of the wood and
associated structural components at
the time of installation (the levels
may look fine at the specific point
in time when they are collected).
The expected impact of environmental
controls such as air conditioners,
humidifiers and dehumidifiers, as
well as the cyclical changes in
humidity in that geographic region,
must be factored in. When combined,
these factors determine suitable
installation conditions for the
flooring and its future environment.
Don’t mistakenly think that because
flooring has been acclimated prior
to installation that it is has been
acclimated correctly and that
installation can proceed. To ensure
a successful wood floor installation
and a satisfied customer, all
variables relative to moisture must
be identified and addressed.
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