Wood is a living material, and its fibers expand and contract in response to climactic conditions, even after it has been turned into flooring boards. When dry conditions prevail in a room with a hardwood floor, the wood naturally shrinks.
Whether this shrinking will produce gaps between the boards depends on a number of factors, including the type of flooring boards and the methods used to install them.
Hardwood boards retain the shape they had upon installation as long as their moisture content remains uniform. This is seldom the case, though, and a certain amount of separation is considered acceptable, according to Wood Floors Online.
Winter months, when the heater is on, tend to produce dry conditions that cause boards to shrink. In addition, crowning, which happens when the center of the boards swells, can also cause separation.
This depends in part on the ratio of heartwood to sapwood in the boards, because sapwood has an increased tendency to expand and contract.
Types of Hardwood Boards
The density of the hardwood in your floor, the width of the planks and their composition all affect their tendency to expand and shrink. Softwoods like pine and fir, which have open grains, are the most susceptible to movement, particularly if the planks are wide.
In contrast, close-gained hardwoods like mahogany are relatively stable. Moreover, engineered flooring, constructed in laminated layers like plywood, tends to move less than raw wood flooring.
The amount of movement you can expect from your flooring material will be apparent in the amount of warpage you observe when you unpack the boards for installation.
When you install a hardwood floor, you should spread the boards around the room and leave them for three days to come into equilibrium with the climate of the room. Failing to do this means that the boards will have to achieve this equilibrium after they have been nailed, which can lead to cupping or separation.
You may also find gaps in your floor if you fail to use a sufficient number of nails to hold the boards. Neither problem is easy to resolve after the floor has been installed.
Separation between boards in your floor may be a result of the foundation settling. You may notice other related effects to confirm this, such as cracks in drywall seams, or water tending to pool in various parts of the floor.
Separation can also be the result of a subfloor that lacks correct composition to hold the flooring nails. Particle board, which some installers use as a subfloor, is notoriously susceptible to weakening over time, specially if it gets wet.
You can't correct these problems easily, but you can fill the gaps with a high-quality latex filler and refinish the floor if they become extreme.