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Humidity Levels are Dropping!

engineered wood hardwood hardwood maintenance hardwood replacement repairs maintenance repair

Fall is here and temperatures are cooling down, which means interior humidity levels are dropping too!  You will be turning your heat on and your wood floors will be affected, so make sure you know about the different seasonal related issues that will arise.

Nearly every wood floor will have some seasonal separation between the boards (gaps) during the fall and winter months.  These gaps happen because when you turn the heat on, moisture gets taken out of the air, dropping the humidity level.  To match the environment, your wood looses moisture too, which causes them to shrink.  As each board shrinks, the gaps begin to appear.  But don't fear!  This is normal.  Once winter is over and the season begin to change back to being warm again, the humidity levels will rise and your wood boards will expand and the seasonal gaps will disappear. 

NOTE: You don't have to wait for the seasons to get warmer to fix these gaps.  You can regulate the realative humidity levels in your house on your own with supplemental humidification.

Now, these seasonal gaps are more prominent with solid wood flooring products than with engineered wood flooring products.  The structural composition of the engineered flooring allows it to be more dimensionally stable than the solid wood.  However, it will still react to low humidity levels and will actually show itself differently.  Instead of having gaps, the engineered wood flooring products will actually begin to dry cup when the humidity level is kept below the manufacturers recommended levels for too long.  Dry cupping happens when the wood product loses moisture and begins to shrink across the outer face which can actually put enough force on the core material to pull the edges of the plank upward resulting in a cupped appearance across the width.

Besides normal gaps and dry cups, there can also be abnormal gaps in your flooring.  Abnormal gaps are more prevalent in new construction scenarios, because homebuyers and homebuilders have become more energy-conscious which can inadvertently effect the ability of woods floors to perform if the relative humidity levels are not properly addressed and maintained.  More energy-efficient homes prevents warm or cool air loss, but also seals in the new home's moisture.  Moisture from the building process (water is used in many building components like placing concrete, drywall, plaster and others) is not allowed to dissipate fast enough.  Often times, the wood floor and wood subfloor will take on this moisture and when the home finally dries out (about 6-12 months) the flooring materials shrink.  When the flooring shrinks this time, the result could be abnormal gaps and will likely never completely close back up during the humid months if the environment remains at those conditions.  These types of gaps may involve wood or engineered wood flooring.  A thourough inspection should be conducted to determine the actual cause when the gaps are deemed "abnormal" because they can be caused in many different ways including:

  • structural movement
  • improper fasteners
  • inadequate subfloor
  • improper adhesive application
  • edge-crush from prior exposure to extreme moisture
  • poorly insulated heating duct below the floor


Assessing Gaps

The first test should always be checking the interior temperature, relative humidity, and moisture content of the flooring and comparing those results to the season.  In a seasonal situation, the moisture content will likely be quite low.  If during these tests the results show it is not seasonal, more investigation will be necessary and an NWFA Certified Inspector can provide a thorough, unbiased inspection to help find the cause.



Regardless of any environment the floor has been exposed to, or that exists when inspected, removal and replacement of a wood floor to get rid of the gaps is unnecessary.  It is usually best to leave the gapped floor in place and repair as necessary.  Once the floor has been acclimated to the home's environment, it is far more likely to remain stable and can even regain the appearance it had when new with no loss of service with professional repairs.


If you have truly normal gaps, no repairs are necessary.  If a filler is used to fill gaps when they appear (when it's dry), it may actually permanently damage the floor when the moisture returns and starts expanding again.  The fillers can crush the wood fibers along the edges of the boards and create even bigger gaps.  A normal gap might have even been purposefully built into the floor as an internal expansion joint.  By adding humidity, seasonal gaps will swell and the gaps will disappear.  You can do this by: (1) wait for the humid season while living with the seasonal gaps, or (2) acquire an adequate humidification system to introduce humidity to your home.


If you have an engineered floor that has dry-cupped, the floor will often return to its intended state once the humidity levels have been returned to within the manufactures tolerances.  However, in extreme cases where there is ply separation (where the wear layer delaminates from the core material) or wood-shear (when the stresses exceed the strength of the wood fibers), the affected boards must be replaced.


Even floors that have gone through environments to cause abnormal gaps can be repaired so the gaps almost disappear.  If the floor has a surface finish, a matching filler can be troweled into all the gaps.  When it's dry, the floor will likely need to be relocated.  For larger gaps, inserting slivers may be necessary and even in some cases, individual board replacement may be necessary.
Remember:  The only way to completely alleviate seasonal fluctuations in wood flooring is to control the ambient conditions in your home.  During the winter months, when the heat is turned on and the air dries out, adding humidification will not only minimize these effects on your wood flooring, but will also assist in the overall health of your entire home.


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