Cupping is the condition of
the edges being higher than the center of the
boards, providing a wavy, washboard appearance
(photo below). The cupped
plank, or strip, has a concave or dished
appearance. Cupping is one of the two most common
complaints in the hardwood flooring industry, yet
least understood.
 Cupping
of wide boards, four inch to seven inch widths is
characteristic to a degree. Boards are rectangle
in shape and the tree is round, giving the board a
natural tendency to be round, depending on the cut
of the board. Wide width cupping is not normally
seen in normal lighting but noticed in reflective
light. Slight cupping of wide width planks is
characteristic and not associated with this
discussion.
The most common condition causing cupping is the
sub-floor having a higher moisture content than
the wood itself. The moisture moves from the
sub-floor into the drier wood flooring, leaving
the bottom higher in moisture content than the top
of the board, causing the bottom to swell more
than the top of the board. The top is not swelling
at the same rate as the bottom, leaving the top
smaller and cupped.
An example of this condition would be a new
construction home without heat or air conditioning
when the floor is installed. The condition of new
construction buildings are generally wet after
with the sub-floor high in moisture content. The
installers arrive to install wood that is drier
than the sub-floor. The heat, or air conditioning,
is turned on after the installation, drawing the
moisture from the sub-floor into the drier
hardwood flooring resulting in the cupped
condition.
Homes with crawl spaces require placement of a
vapor barrier on the ground to stop the capillary
water movement from the soil into the buildings
sub-floor. After placement of the vapor
barrier, the sub-floor must be given time to
acclimate to the new conditions of the crawl space
changed by placement of the vapor barrier. Failure
to allow time for the building to acclimate to the
new conditions may result in cupping due to the
higher moisture content in the sub-floor compared
to the wood flooring.
Professionals know the need for the crawl space
vapor barrier, but novices are unaware, and do not
as a general rule, take the time to investigate
the site. The novice, or untrained installer,
installs the wood flooring without acclimating to
the conditions of the site, does not check
sub-floor moisture content and installs the new
flooring without a vapor barrier placed on the
ground. Cupping could easily appear within days.
To prevent cupping, remember that the wood must
contain the same, or nearly the same, moisture
content of the sub-floor, the home must be
acclimatized to In use conditions before and
during the installation, and moisture barriers
must be in place. |
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Contributed By: Ray Darrah |
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Location: Tampa, Florida |
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Primary Business: Hardwood
Floor Inspections |
| Bio
Page:
See Ray's Bio Page |
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Website:
Flooring Expert.com |
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Phone: (813) 426-3632 |
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