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Edition 04

Nurtured naturally



By Anthony Kamande

In a comfortable home with slight humidity variations through the seasons, wood flooring responds by expanding and contracting, a situation that calls for solutions. The problematic changes may be noticeable on the wood during warm and humid weather because the floors expand. During dry weather, wood contracts.

The 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 home owners expect is to install humidity controls and ensure that they are functioning before the flooring is installed.

Humidity controls

Home owners who choose hardwood flooring literally invest in a floor that will last 40 years or more. Such owners should therefore protect that investment by installing humidity controls – a feature that helps the floor maintain a beautiful and trouble-free appearance. Nearly every floor endures some separation between boards. In cold seasons, when homes are heated and the air is dry, wood flooring gives up some of its moisture and therefore shrinks. When that happens, thin cracks appear between. This is normal. As it is acceptable, customers should not panic and start calling the installers at the first sign of cracks. Once the indoor heat goes off, and the indoor environment regains moisture, most of these cracks will close up.

 Cure of cracks

Floors with light stained woods and naturally light woods like maple tend to show cracks more than darker, wood-tone finished floors.

To cure the cracks, it is advisable for homeowners to add moisture to the air during dry periods. It’s their choice-live with the cracks and wait until warmer seasons, or else add humidity by opening the dishwasher after a rinse cycle, switching off the bathroom fan or hanging laundry to dry in the basement near the furnace. Better yet, install a humidifier in the furnace, or an exterior air vent for the furnace burner.

“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. The wood is wetter on the bottom of the board than on the top. The moisture imbalance can be proven by taking moisture meter readings at different pin depths.

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 noted that some slight cupping and crowning may occur naturally, and should be tolerated.

 Buckled floors

The “buckling” of hardwood floors-when the flooring literary pulls away from the subfloor, lifting up to several inches in one or more placesis one of the most extreme reactions to moisture that can occur. Fortunately, it is not a common occurrence.

Buckling happens most often after a floor is flooded for a time, but there are numerous other causes. On nailed floors, insufficient nailing, incorrect nails or incorrect subfloor construction are possibilities. On glue-down floors, the causes range from the use of incorrect or insufficient mastics to an inadequate mastic transfer, a subfloor separation or a subfloor contamination. In flooded hardwood strip flooring, the swelling stress is theoretically high enough to push out walls. However, before that occurrence the nails or the glue holding the flooring to the subfloor will usually give way, so that the floor bulges upward. If buckling floors are caught early, spot repair and replacement may be possible.


Anthony is the managing director of Natural Wood Floors

based in Nairobi and can be reached on anthonykamande@