Ways to Rectify Cupping in a Solid Wood
February 10, 2021
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Cupping or dishing in solid hardwood means the boards raise
slightly at their edges making the hardwood flooring uneven
across its width. The cause of cupping is an imbalance of
moisture through the timber. This can be a result of a spillage
on the home flooring, or
because of the hardwood flooring gaining moisture from the sub-
Taking moisture reading of the underside of the timber and
comparing this with a reading taken from the upper side will
Wood always expands when it takes on moisture. It therefore
follows that moisture on the underside of the wood will make
the underside expand laterally. However, the upper side of the
wood which has not absorbed any moisture, so this stays at near
its original size. The immense strength of the expansion of the
underside of the wood is what makes the edges of the wood curl.
On nearly every incidence of cupping that I have inspected, the
flooring was laid onto a solid floor using adhesive- meaning
that the sub-floor was too high moisture content. A quick and
simple way of identifying the problem is by taking a moisture
reading of the sub-floor. Usually this is just a matter of
drilling a small hole into the sub-floor between the gaps in
the board, and inserting the probe from a moisture meter. The
reading of the sub-floor should be around 9- 11% moisture
content. If it is higher, then this could be the source of the
As part of an inspection process, I also look for evidence of
leaks from appliances e.g. dishwashers, and leaks from heating
pipes, and poor or zero ventilation in the room.
I also take a reading of the humidity at the time of the
inspection, although this is merely a snapshot of one moment in
time and does not necessarily give an indication of the
humidity at an earlier time that may have caused the cupping.
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