Every winter it happens. You're walking across the living room in socks and notice lines between the boards that weren't there in July. A dime would fit in some of them. Is the floor falling apart?

Almost certainly not. Your hardwood is just reacting to NEPA's winter air. Here's what's going on, what's normal, and when to call someone.

Why hardwood shrinks in winter

Wood is a natural material, and it never fully stops responding to moisture. It absorbs moisture from the air when it's humid and releases it when it's dry.

In summer, NEPA is humid. Your boards take on moisture and swell slightly. In winter, cold outside air holds very little moisture, and your furnace dries the indoor air even more. Your boards give up moisture and shrink. When each board shrinks a little, gaps open between them.

This is called seasonal movement. It's the reason a hardwood floor is never truly finished moving.

What's normal

Generally, seasonal gaps are considered normal when they:

• Show up in the heating season and close up again in spring or summer
• Are fairly small and spread fairly evenly across the floor
• Don't come with cupping, buckling, or soft spots

Wider boards tend to show bigger gaps, since there's more wood to shrink. Older NEPA homes with forced hot air heat often see more gapping than homes with radiators or humidified systems.

When to worry

Call a flooring pro if you notice:

• Gaps that don't close when the weather turns humid
• Very wide gaps concentrated in one area
• Cupping (edges of boards higher than the center), which usually points to moisture coming from below
• Crowning or buckling (boards lifting or arching)
• Gaps along with squeaks or soft spots, which could mean a subfloor problem
• Gaps near a sink, dishwasher, or exterior door, which can signal water damage instead of normal shrinkage

Those aren't seasonal movement. They're symptoms worth investigating.

How to prevent winter gaps

The single best tool is a humidifier. Many hardwood manufacturers recommend keeping indoor relative humidity in a moderate range year-round, often somewhere around 35 to 55 percent. Check your floor's warranty for its exact numbers, since some warranties require it.

• Buy a cheap hygrometer and see what your humidity actually is. Many NEPA homes drop into the 20s in January.
• Run a whole-house or room humidifier during heating season.
• Don't crank the heat way up and down. Steady is better for wood.
• Run a dehumidifier in summer to keep the swing smaller in both directions.

Can you fill the gaps?

Usually, you shouldn't fill seasonal gaps. If you fill them in winter, the filler has nowhere to go when the boards expand in summer. It can get pushed up out of the gap or put stress on the boards.

The better fix is controlling humidity so the gaps shrink on their own. For permanent gaps that never close, a pro can evaluate options.

Love the look of wood but tired of the drama?

Hardwood is beautiful, and plenty of NEPA homeowners love it. But if seasonal gaps, water worries, and humidity management sound like more than you signed up for, waterproof vinyl plank gives you a realistic wood look without the movement. It's far more stable through temperature and humidity swings, and it doesn't care about salt or spills. See how it compares for warmth and what survives road salt.

Many homeowners split the difference: hardwood in the living room and dining room, vinyl in the kitchen, entry, and basement.

Installing hardwood this winter?

You can, with proper acclimation and humidity control. Our guide to installing flooring in winter covers it. Browse hardwood flooring or vinyl flooring, then book a free estimate to talk through what fits your home.

Want it done before guests arrive? Our holiday installation timeline shows how to plan backward from the date.

Frequently asked questions

Are gaps in hardwood floors normal in winter?

Yes, in most cases. Dry winter air makes boards shrink, and small, evenly spread gaps that close again in spring or summer are normal seasonal movement.

What humidity is best for hardwood floors?

Many manufacturers recommend indoor relative humidity in a moderate range, often around 35 to 55 percent. Check your floor's warranty for its exact numbers.

Should I fill gaps in my hardwood floor?

Usually not. Filler added in winter has nowhere to go when the boards expand in summer, so controlling humidity is the better fix.

When are hardwood gaps a problem?

Call a pro if gaps don't close in humid weather, are very wide in one area, or come with cupping, buckling, soft spots, or nearby water sources.