Hardwood floors are made from “kiln dried” material, but are subject to the natural process of shrinkage and expansion. In the winter, when the humidity is lower in your home, the wood will separate slightly especially near heating vents. High humidity on the other hand, will cause expansion and may lead to cupping or swelling in the center of the board. The cause of ‘squeaks’ in some hardwood floors is the common ‘settling’ of pre-finished hardwood or excessive humidity or dryness in the home. It is imperative that the humidity level of your home always be properly monitored and controlled.
Air conditioning or the use of a dehumidifier in a new home will significantly reduce the high moisture content found in all new homes.
Please refer to the following article from the National Wood Flooring Association regarding hardwood floor care.
TECHNICAL PUBLICATION NO. A100
In a comfortable home with slight humidity variations through the seasons, wood flooring responds by expanding and contracting. These changes may be noticeable. During warm, humid weather wood expands. During dry weather wood contracts. This seasonal movement is a normal characteristic of wood flooring and it never stops regardless of the age of the wood. One of the best ways to ensure that wood flooring will give the performance homeowners expect is to install humidity controls.
WORKING WITH HUMIDITY CONTROLS
A homeowner who chooses hardwood flooring is making an investment in a floor that will last 40 years or more and he or she should protect that investment by installing humidity controls – a tool that helps the floor maintain a beautiful, trouble-free appearance.
CRACKS AND SEPARATIONS BETWEEN BOARDS
Nearly every floor endures some separation between boards. In winter, when homes are heated and the air is dry, wood flooring gives up some of the moisture and therefore shrinks. When this happens, thin cracks appear. This is normal and homeowners should be forewarned of this. It is acceptable and customers should not be calling the installers at the first sign of cracks. Once the indoor heat goes off in the spring and the indoor environment regains moisture, most of these cracks will close up. Cracks in winter during the drier months, may easily develop to the thickness of a dime for solid 2 ½ inch wide strip oak floors. Floors with light stained woods and naturally light woods like maple tend to show cracks more than darker, wood-tone finished floors.
CUPPING AND CROWNING
“Cupping and crowning” are common complaints that develop with high humidity. Both problems occur across the width of the flooring material. Cupping is when the edges of a board are high and its center is lower. It can occur after water spills onto the floor and is absorbed by the wood, but high humidity is more often the cause. If the wood expands significantly, compression set can result as the boards are crushed together, deforming the boards at the edges. Cupping is caused by a moisture imbalance through the thickness of the wood, as the wood is wetter on the bottom then on the top of the board. Taking moisture meter readings at different depths can prove moisture imbalance.
The first step in repairing a cupped floor is to identify and eliminate the moisture source. In the kitchen, it may be a leak from the dishwasher or icemaker. From outdoors, it might be the terrain of the lot with rain and runoff not moving away from the house and foundation. Indoor, the humidity may need to be controlled or a plumbing leak may be causing excess moisture in the basement, which migrates up into the subfloor and from there into the wood flooring. Once the source of the moisture is controlled, cupping can usually be cured. The floor may improve on its own as it dries out over time. At other times, fans may be needed to speed the drying process. Once the moisture content is stabilized, the floor can be reassessed. Choices may be to do nothing at all, to recoat the floor or to sand and refinish the floor. However, it should not be sanded until moisture meter readings indicate the floor has thoroughly dried.
Crowning is the opposite of cupping. The center of a board is higher than the edges. Moisture imbalance is sometimes the cause of crowning if excessive moisture is introduced on the top of the floor, perhaps from water used in maintenance or plumbing leaks from an overhead sprinkler system. However, a common cause is that the floor was previously cupped, but was sanded at the wrong time – before the moisture content returned to normal and the board flattened on its own.
It should be known that some slight cupping and crowning may occur naturally and should be tolerated. The bark sides of lumber shrinks and swells more then the side closest to the center of the tree. Using a bevel-edged flooring product with a satin finish, rather than square-edge flooring with a high gloss finish can minimize its appearance.
SOME TIPS ON MAINTENANCE
- Sweep your floors or use a dust mop daily, but do not use a household dust treatment, as this may cause your floors to become slick or dull the finish.
- Vacuum your wood floors as often as you would vacuum your carpets.
- Clean your floor’s coated surface with a lightly dampened cloth using a recommended cleaning product and according to the manufacturer’s directions for use.
- Never damp mop a wood floor. In all cases, use minimum water, because water causes deterioration of the wood itself, as well as the finish. Clean only when necessary and clean only the soiled areas.
- Buy a “floor care kit” that your installer or flooring retailer recommends instead of counting on home-made remedies such as vinegar and water to clean your floors. Different finishes have different requirements and it’s best to follow professional advice in this area.
- Clean light stains by rubbing with a damp cloth. Avoid using mops or cloths that leave excessive water on the floor. Never let a spill of water dry on the floor.
- Control humidity levels by use of a dehumidifier or humidifier.