Hardwood Gapping

Hardwood Gapping



Here is some knowledge to pass on. After surviving the winter heating months which may last for several
months’ wood floors tend to shrink or gap as a direct result of the heat running - a direct result of low
Relative Humidity within the home. Furnaces tend to dry the air out and in turn the wood will dry out.
Because of this the wood industry recommend to maintain the relative humidity within a home
or building between 35%-55% and in doing so will minimize the expansion and contraction of the wood
floors. In some areas of the country whether due to low humidity in the region or because of extended
heating seasons a humidification system may be needed to help maintain the humidity within the
structure. The good news is that once we move out of the heating season the relative humidity typically
will go back up and the wood will gain some moisture that is now found within the air and the gaps will
close back up. This is known as seasonal gapping and is normal for wood floors.

What does this mean to you? Typically we see receive more calls for gapping complaints at the end of
the winter months, and hopefully this will give you and your customers a better understanding of why
this happens. Remember that wood is hygroscopic – meaning that when exposed to air wood will either
gain or lose moisture until it is in equilibrium with the temperature and humidity of the air. Additionally
different species of wood will expand or contract at different rates due to their coefficient of expansion.
Hickory has a higher coefficient than Oak or Maple. Lastly the wider the plank the more expansion or
contraction is to be expected when the humidity becomes higher or lower.
To help combat low humidity there are a number of suggestions to help prevent the wood from drying
out in the winter months
 
1. Humidifier
2. Boiling water on the stove
3. Opening the dishwasher at the end of the wash cycle
4. Purchasing a hygrometer to monitor the relative humidity within the home