Gaps Between Hardwood Floorboards in Winter: Normal or a Problem?

Oct 13

3 min read

Updated: 1 day ago

Some gaps between hardwood floorboards in winter are normal. Wood shrinks as it loses moisture, and indoor heating dries the air, so solid boards contract and thin gaps open between them. When humidity returns in spring and summer, the boards swell and most of those gaps close again.

How big is too big?

A common rule of thumb is that seasonal gaps about the thickness of a dime are normal for solid hardwood. Wider boards move more than narrow ones, so a 5-inch plank floor will show larger seasonal gaps than a 2-1/4-inch strip floor. Gaps that are wide, uneven, or do not close in humid months suggest something more than normal seasonal movement.

Signs the gapping is a real problem

Gaps stay open all year, even in humid summer months.
Gaps appear suddenly, in one area, or alongside other symptoms like cupping or squeaks.
Several boards move together and leave one large gap ("panelization"), often caused by finish gluing boards together at the edges.
Gaps open near heat sources such as radiant heating, heating vents, or sunny windows.

What causes excessive gapping

Very dry indoor air, often below 30% relative humidity during the heating season.
Flooring that was installed with too high a moisture content and then dried out in service.
Radiant heat systems operated at high surface temperatures.
Wide solid planks installed where an engineered product would have been more stable.

How to reduce gaps

Keep indoor relative humidity in a steady range, generally 30% to 50%, with a whole-house humidifier if needed in winter. Avoid filling seasonal gaps with wood filler, which can crack out or push boards apart when they swell in summer. If gaps do not close by late summer, have the floor inspected before making repairs.

When to call an inspector

If you are being told the gaps are "normal" but they look excessive, or a warranty claim has been denied for "environmental conditions", an independent inspection measures moisture content and humidity and compares them with the manufacturer's requirements. National Wood Floor Consultants, led by NWFA Certified Wood Flooring Inspector Joe Avila, serves New Jersey, New York, Pennsylvania and major U.S. cities. Call (908) 232-6600.

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Quick Answers About Winter Gaps In Hardwood Floors

Are Gaps In Hardwood Floors Normal In Winter?

Some are. Heating dries indoor air, solid boards shrink and thin gaps open between them. Most close again when humidity returns in spring and summer.

How Big A Winter Gap Is Too Big?

A common rule of thumb is that seasonal gaps about the thickness of a dime are normal for solid hardwood. Gaps that are wide, uneven or stay open through humid summer months suggest a problem.

Should I Fill Winter Gaps In My Hardwood Floor?

Usually not. Wood filler in seasonal gaps can crack out, or push boards apart when they swell again in summer. Steady indoor humidity is the better fix.

When Should Winter Gaps Be Inspected?

If the gaps do not close by late summer, appear suddenly in one area, come with cupping, or a warranty claim was denied for environmental conditions, an independent inspection can find the cause.

About The Author

Joe Avila is the founder and lead consultant of National Wood Floor Consultants, with 26 years in wood flooring. He is an NWFA Certified Wood Flooring Inspector, installer and sander, and teaches accredited AIA, ASID and IDCEC continuing education for architects and designers. His project experience includes Montclair University, One Wall Street, institutional and landmark buildings, and luxury residences and penthouses, and he pioneered subfloor sound-attenuation systems for New York City apartments. Read Joe's full profile.