During the winter, even the most carefully installed wood floors tend to dry out and shrink. The floor behaves that way because of wood’s relationship with moisture in the air. Air with a low moisture content, or low relative humidity (RH), causes wood to lose moisture. When wood loses moisture, it shrinks. To control winter-related shrinkage of flooring and the gaps there are basically six options.
1. Use engineered wood flooring.
Engineered flooring is traditionally more stable than solid wood due to the fact that the plywood cross hatched pattern under the real wood veneer is not given as much room to expand and contract as real wood. Keep in mind that all engineered woods have a range of moisture levels that are covered under manufacturer’s warranties. Take a look at what your warranty covers before you chose your product!
2. Use smaller, thinner boards.
Narrow boards will shrink less than wide boards. A 5-inch-wide plank will shrink twice as much as a 2¼-inch-strip. So the size of the gap between 5-inch boards will be twice as big as the gap between 2¼-inch boards. In addition, narrower boards have more nails or staples per sq ft holding the board to the subfloor. This also minimizes gapping and other warping.
3. Use a different, more stable species of wood.
Some species are more stable than other species. A 5” wide board of hickory will shrink more than a 5” wide board of red oak. Many websites online will give you information on the stability of the flooring you’re looking for to determine its likelihood of cupping or gapping.
Along the same line of varying dimensional stability, quartersawn flooring shrinks about half as much as flatsawn flooring for the same amount of moisture change, so quartersawn flooring will have smaller gaps than flatsawn flooring under the same circumstances.
4. Address the moisture issues.
Gapping usually occurs when the flooring dries from its summertime high moisture levels. So, to reduce winter gapping, reduce the change in moisture. There are two approaches to keeping winter indoor RH higher.
5. Reduce Ventilation
Ventilation of a house in the winter tends to dry it out. When you bring cold outside winter air into a house and warm it up, the RH of that air drops significantly. To get the RH of this air back up to something respectable, we would need to add moisture. The more ventilation that is occurring, the more this dry air is drying out your home, and the more moisture you need to add. The solution to this part of winter drying is to reduce ventilation. Old windows are often major leakage sites, as are recessed lights and other holes in ceilings and floors. Give your home an energy audit through Mass Save, or another reputable provider, to make sure your windows and doors are air tight when closed.
6. Add Moisture
If the ventilation rate is higher, we need to add more water. If it’s colder or warmer outside, the amount of water changes with the varying temperature. Colder outside air requires more moisture, higher ventilation rates require more moisture, and higher target indoor RH levels require more moisture. Moisture is added to indoor environments from normal household activities and use. When this moisture is not sufficient to meet the needs, a humidifier can be added. Humidifiers can either be stand-alone or attached to a central forced air furnace. Typical residential systems can provide up to about 6 pints per hour according to the National Hardwood Association.
Just be careful not to be adding too much moisture; then you’ll be worried about hurting the building and causing condensation or, even worse, mold.
So what do we do? Bottom line: Winter weather dries out wood flooring, causing gaps, possibly increasing squeaks and opening surface cracks. Wood will be wood. Physics will be physics. Humidifiers can help some, as can choosing the right wood flooring for the right situation, but only to a certain extent. Be realistic with your wood choices and what type of situation you’re putting your wood floors in. For any questions, always contact a professional!!