Gym Floor Gaps in Winter: What's Normal

Small gaps between gym floor boards in winter are usually normal. Heating dries out the indoor air, and maple gives up moisture and shrinks, so seams open up. Most of those gaps close again when humidity rises in spring and summer. According to the Maple Flooring Manufacturers Association (MFMA), a general rule is that if you can fit a quarter in a crack, it is considered excessive, and that’s when you should call a gym floor professional.

Here’s why winter gaps happen, how to tell normal shrinkage from a real problem, and what you can do to keep gaps small.

Why Gym Floors Get Gaps in Winter

Wood is hygroscopic. That means it absorbs moisture from the air when humidity is high and releases it when the air is dry. MFMA explains that when humidity rises, a wood floor absorbs moisture and expands, and when humidity falls, it releases moisture and shrinks (MFMA, Daily Floor Care).

In winter, cold outdoor air holds very little moisture. When that air is pulled into the building and heated, the indoor relative humidity drops. MFMA’s humidity guidelines note that higher ventilation rates can lead to drier indoor air, especially in winter, which can cause “excessive shrinking/gapping of the maple flooring boards” (MFMA, Humidity and Temperature Guidelines).

What’s Normal and What Isn’t

Usually normal

Thin, even gaps spread across the floor
Gaps that show up during the heating season and close in warmer, more humid months
Gaps in a newer floor during its first year or two. MFMA notes that maple flooring typically takes a year or two to stabilize through a full cycle of seasons.

Worth a professional look

Gaps wide enough to fit a quarter, which MFMA considers excessive
Gaps that stay open even when the building’s humidity is in range
Boards that are loose, move underfoot or have sharp, raised edges
Gaps in one area only, which can point to a localized problem under the floor
Gaps along with dead spots, squeaks or cupping

MFMA advises that if cracks persist even though the building has been kept between 55 and 75 degrees and 35% to 50% relative humidity (or no more than a 15% swing), you should contact your flooring installer.

How to Keep Winter Gaps Small

Keep humidity in a steady range

MFMA recommends keeping indoor temperature between 55°F and 75°F and relative humidity within a 15% range, such as 35% to 50%. The key word is steady. Big swings cause the most movement.

Don’t shut the HVAC down over breaks

MFMA does not recommend shutting HVAC systems down for extended periods, including weekends, holidays and summer break. Over a long holiday break, a cold, closed-up gym can swing hard in humidity, and the floor will react.

Monitor and record conditions

An inexpensive hygrometer near the floor lets you see what the wood is experiencing. Write readings down weekly. If you ever need help diagnosing a problem, those notes are very useful.

Use humidification where you can

MFMA recommends humidification and dehumidification systems where available. If you don’t have them, MFMA suggests using damper controls and circulating fans to reduce wide swings.

Should You Fill Gaps in a Gym Floor?

In most cases, no. Seasonal gaps in a maple sports floor are expected to close as humidity rises. Filling them can cause problems when the boards expand again. A gym floor is also a system, with expansion space built in at the walls and around fixtures, so it can move without damage.

MFMA also warns: never attempt to modify or repair your MFMA sports floor without first consulting your MFMA contractor. If gaps are excessive or boards are damaged, a professional should assess the cause first, whether that’s environment, installation or moisture from below. Our gym floor repair services cover board replacement and other fixes.

Gaps vs. Cupping and Buckling

Gaps are the dry-season problem. Cupping and buckling are usually the opposite: too much moisture. If your floor shows gaps in winter and cupped or raised boards in summer, the building’s humidity swings are likely too wide. Read our guides on gym floor buckling and cupping and humidity and hardwood gym floor care.

Plan Repairs and Refinishing for the Right Season

If boards need replacement, timing and conditions matter. New wood should match the moisture conditions of the existing floor. Talk to your contractor about the best time for repairs. Repairs are a separate job from a screen and recoat, and they can be added to a full sanding and refinishing if you ask. When a floor is at the end of its life, we’ll tell you honestly whether replacement makes more sense.

Frequently Asked Questions

Are gaps in a hardwood gym floor normal in winter?

Yes, small seasonal gaps are normal. Maple shrinks in dry winter air and usually swells back in more humid months.

How big is too big for a gap in a gym floor?

MFMA’s general rule: if a quarter fits in the crack, it’s considered excessive. Call a professional to find the cause.

Will the gaps close on their own?

Seasonal gaps usually close as indoor humidity rises. If they stay open when your building is in the recommended range, have the floor inspected.

Can I fill the gaps with wood filler?

It’s generally not recommended for seasonal gaps in a maple sports floor, because the boards need room to expand. Talk to a gym floor contractor before filling anything.

Worried About Gaps in Your Gym Floor?

J&J Gym Floors has inspected, repaired and refinished gym floors since 2001. With more than 20 years of experience and 50,000+ projects, we can tell you whether your gaps are normal or a sign of something bigger. Call 973-801-7219 or email john@gymfloors.com. We also handle New Jersey gym floor refinishing and repairs once the season settles.