New Hardwood Floors Have Gaps Between Boards — Is This Normal?

Quick Answer

Small gaps between new hardwood floor boards are normal and expected during dry seasons (winter in most climates). Solid hardwood expands and contracts with humidity changes -- boards swell in humid months and shrink in dry months, opening gaps of up to 1/32 inch in width. Gaps that close in summer and reopen in winter are seasonal and nothing to worry about. Gaps that appeared immediately after installation and never close likely indicate the wood was not properly acclimated before installation, was installed with too much moisture content, or the home's humidity is consistently too low.

Wood Moves. That Is What It Does.

Hardwood is hygroscopic, meaning it absorbs and releases moisture from the surrounding air. When the relative humidity in your home is high (summer, rainy seasons), the wood absorbs moisture, swells slightly, and the boards press tighter together. When the humidity drops (winter, when heating systems dry the air), the wood releases moisture, shrinks, and gaps appear between boards.

This is not a defect. It is the fundamental nature of the material. Every hardwood floor that has ever been installed does this to some degree. The question is not whether your floors will gap, but how much gapping is acceptable.

For most species installed at correct moisture content, seasonal gaps should be barely noticeable -- hairline gaps of 1/64 to 1/32 inch that close up completely in humid months. If you can easily fit a coin in the gap, something went wrong during installation or the home's environment is problematic.

When Gaps Indicate a Real Problem

The wood was not acclimated. Before installation, hardwood flooring needs to acclimate to the moisture conditions of your home. This means storing the unopened or partially opened boxes of flooring in the rooms where they will be installed for a minimum of 3-5 days (and up to two weeks for wider boards or significant climate differences). During this time, the wood adjusts its moisture content to match the home's environment.

If the flooring was installed straight off the delivery truck -- especially if it came from a humid warehouse and went into a dry, heated home -- the boards were swollen with excess moisture at the time of installation. As they dried out in your home, they shrank, creating gaps that were not present on install day. These gaps may partially close in summer but will never fully disappear because the boards have settled into their new equilibrium.

The subfloor was wet. A concrete subfloor that was not fully cured, or a plywood subfloor that got wet during construction, can transfer moisture into the hardwood from below. The boards absorb this moisture, swell during the first few months, then shrink as the subfloor dries. This produces gaps that show up weeks or months after installation and may be accompanied by cupping (edges higher than centers).

The home is too dry. Hardwood flooring manufacturers specify an acceptable humidity range, typically 30-50% relative humidity. In cold climates with forced-air heating, indoor humidity can drop below 20% in winter. At these levels, even properly installed and acclimated flooring will gap excessively. The wood is shrinking beyond its design parameters.

The wrong species for the conditions. Some wood species move more than others. Red oak and hickory are relatively stable. Maple moves more. Exotic species like Brazilian cherry (jatoba) can be extremely reactive to humidity changes. If you installed a high-movement species in a home with wide humidity swings, you will see more gapping than average.

What You Can Do About It

Control indoor humidity. This is the single most impactful thing you can do for your hardwood floors. Use a humidifier in winter to keep relative humidity above 30% (ideally 35-45%). In summer, air conditioning naturally dehumidifies, so the upper end usually takes care of itself. A simple hygrometer (humidity gauge) costing ten to fifteen dollars lets you monitor conditions.

Maintaining consistent humidity does not just help with floors -- it also reduces issues like drywall tape bubbling and protects wooden furniture, musical instruments, and anything else that reacts to moisture changes.

Do not fill seasonal gaps. This is a common mistake. Homeowners see winter gaps and want to fill them with wood filler, caulk, or putty. When summer arrives and the boards swell, the filler prevents the boards from closing naturally. The boards push against the filler and each other, causing buckling, cupping, or the filler popping out in chunks. If the gaps close every summer, leave them alone.

Fill permanent gaps carefully. If you have gaps that never close (from installation issues), they can be filled, but use a flexible filler designed for wood floors -- not rigid wood putty. Color-matched flexible fillers accommodate the small amount of seasonal movement that still occurs. Apply it when the humidity is at its annual midpoint (spring or fall) so the filler is neither compressed nor stretched to its limits at any time of year.

Consider a humidifier system. For homes in very dry climates or with persistent humidity problems, a whole-house humidifier connected to the HVAC system provides consistent humidity control without the hassle of refilling portable units. These systems cost $200-500 installed and can be set to maintain a target humidity range automatically.

Engineered vs Solid Hardwood

Engineered hardwood is specifically designed to minimize this problem. It consists of a thin layer of real hardwood on top of a cross-laminated plywood base. The cross-lamination constrains the wood's movement in the horizontal plane (the direction that causes gaps) while still allowing it to respond slightly to humidity. Engineered hardwood gaps far less than solid hardwood and is the recommended choice for environments with poor humidity control, over concrete slabs, or in below-grade installations like basements.

If you are planning a hardwood installation and are concerned about gapping, engineered flooring is the safer bet. It looks and feels identical to solid hardwood on the surface but behaves significantly better dimensionally.

How Much Gap Is Too Much?

As a general rule, the acceptable gap width is proportional to the board width. For 2-1/4 inch strip flooring, seasonal gaps should not exceed the thickness of a business card. For wider plank flooring (5 inches and up), gaps up to 1/16 inch in dry conditions are within normal range.

Gaps wider than 1/8 inch in any season, gaps that run the full length of a board rather than just in spots, or gaps that appeared immediately after installation and never close -- these are signs of a problem that goes beyond normal seasonal movement. In these cases, the installation company should be contacted to assess whether the flooring was installed properly and within moisture specifications.

Many installation warranties require that the homeowner maintain humidity within the specified range. If your home's humidity dropped to 15% all winter because you do not use a humidifier, the installer may not be liable for the resulting gaps. Check your warranty terms.