The Effect Of Moisture and Fluctuating Humidity on Floorboards

Fluctuations in Humidity

Swings in humidity levels can warp all kinds of timber, new and old. It may seem like poor workmanship, as humidity fluctuations which are significant enough to case warping are generally unnoticeable. Depending on the time of year, you may see gaps forming between the boards or you may see the boards swell to the point where they begin to cup.
 
Ventilation
  
Signs of inadequate ventilation include noticeable 'musty' smell in the space underneath the floor, which may even at times spread into the home. This can even result in mildew on the insides of walls.

Cupping

When moisture absorbed from underneath results in swelling on the underside of the board, which can result in the edges of the board lifting, and a concave shape developing. This is called cupping and will be more noticeable in wide-plank floors.  
 

  
Moisture from above

Reverse cupping (crowning) is also possible, with floorboards developing a convex shape. This is due to moisture from above, such as flooding. This can also result from situations where sanding has been previously carried out, but the boards have then returned to their normal shape after correction of a moisture issue.

Doming

Doming occurs when insufficient space has been provided for the timber to expand. This can result in the boards themselves lifting up in a convex form. 

If you can identify the cause, there may need to be any further action taken, as when the cause is removed, the wood will quite likely return to normal.

What can you do about it?
 
Match the humidity levels inside and outside your home where possible. This can be as simple as using a humidifier in the winter and a dehumidifier in the summer. 

Give your wood a chance to correct itself 

Temporary warping can often be corrected by simply allowing the wood to naturally return back to its usual shape. 

Check moisture levels to identify potentially serious moisture issues

To check moisture levels, you can purchase a hygrometer, which is also known a a 'moisture meter'. Steer clear of the cheaper versions as their readings may be inaccurate.  Never allow a 20 % difference between your floor boards' humidity and the humidity within your home. 

Tips

• Check for excessive moisture
• Never allow a 20% humidity difference between your floor boards' humidity and the humidity inside your home.
• Use a dehumidifier in the summer and a humidifier in the winter.
• Give floors a chance to correct themselves