Moisture and wood flooring, hello problems.

The nobility of wood flooring is undeniable. We love the natural cachet it gives to the decor and appreciate it for its warmth.You should know that all this could quickly disappear if you have a moisture problem. Be warned, humidity can cause serious damage to your wood floor. If your home has an inadequate humidity level, below 40% or above 50%, your wood floor may suffer irreparable damage. Since wood is a natural material, it is more likely to react to changes in humidity. This is why problems often occur during season changes.

 Wood (hygroscopic woody material - material that tends to absorb moisture) reacts to the humidity and temperature conditions it is exposed to. Wood is said to be dimensionally stable when it has been dried to between 6% and 9% moisture content and stored in humidity conditions between 40% and 50%.

Splits (cracks or checks)

Splits consist of fracture lines on the surface of the planks. There are two reasons why splits can occur, namely: 

  1. Due to deformations created by the movement of the wood (the planks push against each other) in the face of inadequate humidity conditions. 
  2. Due to intensive drying causing intense shrinkage leading to cracks.


Gapping is also a problem related to a lack of humidity in the house. Gapping is the appearance of gaps between wood planks. As soon as the moisture balance is restored, the gaps between the wood planks will disappear since the wood regains moisture and thus expands. Be aware that under certain conditions, some gapping may never close completely. 


This type of problem is probably the most extreme reaction of a wood floor to a high humidity level. In response to abnormally high humidity, the wood floor expands and moves upward from the subfloor (it can rise several centimetres from the subfloor). In cases of buckling, the wood flooring in the affected areas should generally be replaced. 


This type of problem is known under several names such as moist formwork, tiling, concavity or washed plank deformation. We speak of cupping when the edges of the planks are higher than the centre of the plank. Cupping can be caused by three different or concomitant causes, namely:

  1. Relative humidity levels too high;
  2. Washing with intensive water ;
  3. Substrate too wet during installation.


Crowning is not a problem directly related to inadequate humidity conditions. It is actually the opposite of cupping since the center of the board is higher than the sides. This type of problem occurs after the floor has been sanded following cupping problem. Since the edges of the boards are higher, they are sanded to level the floor. Since the wood has not had enough time to expel the excess moisture and return to its original shape, the ends of the planks are now lower after expelling the excess moisture. 

Dry cupping 

Similar to cupping, dry cupping applies only to engineered wood floors. Like moist formwork, the engineered wood floor will undergo cupping (the sides of the planks are higher than the center) if the wood on the surface loses its moisture. This will cause the hardwood portion of the flooring to peel off the substrate to which it is glued. 

 Finally, as you can see, wood is very sensitive to ambient humidity variations. That said, you can prevent moisture problems:

  • Remember to maintain a relative humidity level between 40 and 50%;
  • Allow for an expansion space at your perimeter during installation;
  • Avoid excessive exposure to water, i.e.: clean your floor quickly after any liquid spill;
  • Install a vapor barrier or vapor barrier membrane.
  • In a basement installation, opt for a subfloor that will allow air space under the floor covering. This will allow humidity to circulate better. The frames used to receive the flooring substrate must be installed with staggering joints.
  • Leave your air conditioning on when you are away for a long period of time in the summer. 
  • When you are away for a long period of time, make sure that one of your family members can visit your home regularly to avoid any problems that may arise.