Wood never stops moving
Hardwood is a natural material that exchanges moisture with the air around it continuously. It absorbs water vapour when the air is humid and releases it when the air is dry, and it changes dimension as it does. That is not a flaw in the floor or in the installation. It is what wood does, and it will do it for as long as the floor exists.
What matters is the range. A floor living between reasonable humidity extremes moves a little and stays visually fine. A floor swinging between very humid and very dry moves a lot, and that is when you get the problems people call us about.
What Northwest Arkansas does specifically
Our climate is close to the worst case for wood in one particular respect: the annual swing. Summers here are genuinely humid. Winters are not just cold but dry, and central heating drives indoor humidity down considerably further than the outdoor air alone would.
So a floor here can experience high humidity for months, then drop to very dry conditions for months, every single year. That annual cycle is why gapping in January and tightness in July is such a familiar pattern in NWA homes, and why we spend so much time talking about humidity control at estimates.
Cupping and gapping explained
Cupping is board edges sitting higher than centres. It happens when the underside of the board is wetter than the top, which is common in summer, in homes over crawl spaces, and anywhere with a moisture source below the floor. Mild seasonal cupping that flattens as the house dries out is normal.
Gapping is the winter version. As boards lose moisture they shrink across their width, and the gaps between them open. On a wide plank floor this is more visible than on narrow strip, simply because the same percentage of shrinkage across a wider board produces a wider gap. Gaps that close again in summer are seasonal and are not a failure.
The numbers that actually matter
The practical target is keeping indoor relative humidity roughly between 35 and 55 percent through the year. That band is comfortable for people, and it keeps wood movement within a range that does not show as a problem.
In practice that usually means running a humidifier in winter, when heating dries the air out, and letting air conditioning do the dehumidifying in summer. A cheap hygrometer tells you where you actually are, and most people are surprised by their winter readings the first time they check.
Species and format choices that help
If you are choosing a floor rather than fixing one, this is where the decision has leverage. Quarter sawn and rift sawn wood moves less across its width than plain sawn. Narrower boards produce smaller absolute gaps than wide planks for the same percentage of movement. White oak and hickory are more dimensionally stable than red oak.
Engineered hardwood is the most stable option of all, because its cross layered core resists dimensional change. That is why it is the standard specification for slab levels, basements, and walkout lower levels of the hillside homes that are common in Bella Vista. It is not a lesser product. It is the correct product for that condition.
Acclimation is not optional
Before installation, flooring needs to sit in the house it will live in until its moisture content matches that environment. Installing wood that arrived from a warehouse at a different moisture content guarantees movement afterwards, because the boards will equalise whether they are nailed down or not.
This is the step that gets compressed when a build is running late, and it is the single most common root cause of gapping complaints on new installs. We schedule acclimation into our installation timelines rather than treating it as buffer that can be cut.
Crawl spaces are the usual culprit
A large share of the persistent cupping we see in Northwest Arkansas traces back to what is under the house rather than what is in it. A crawl space with exposed soil and no vapour barrier evaporates moisture upward continuously, and the underside of your floor is the first thing it reaches.
The symptom is cupping that never fully resolves, often worst in the rooms furthest from conditioned air. The fix is not a flooring fix. It is a sealed vapour barrier over the soil, adequate drainage away from the foundation, and in some cases conditioning the crawl space. Do that first, let the floor stabilise over a season, then refinish.
We say this even though it means telling people their flooring job has to wait. Sanding a floor flat while a moisture source is still feeding it just spends the floor's remaining thickness on a problem that will come back.
When to actually worry
Call someone if cupping does not flatten as the season changes, if gaps do not close in summer, if boards are lifting off the subfloor, or if you can feel movement underfoot. Those indicate a moisture source rather than a seasonal cycle: a crawl space without a vapour barrier, a plumbing leak, or a slab without proper moisture mitigation.
Fixing the floor without finding the source is money wasted. We look for the cause before quoting the repair, because a refinished floor over an ongoing moisture problem will simply do the same thing again.
Common questions
Is it normal for hardwood floors to gap in winter?
Yes. Wood shrinks as it loses moisture in dry heated air, and gaps that open in winter and close again in summer are normal seasonal movement rather than a defect.
What humidity should I keep my house at for hardwood floors?
Roughly 35 to 55 percent relative humidity year round. That range is comfortable for people and keeps wood movement small enough that it does not show as cupping or significant gapping.
Why are my floors cupping in summer?
Cupping means the underside of the boards is wetter than the top. In summer that is usually ambient humidity, but it can also indicate a crawl space without a vapour barrier or a moisture source below the floor. If it does not flatten as the house dries, it is worth investigating.
Does wide plank gap more than strip flooring?
Visually, yes. The same percentage of shrinkage across a wider board produces a wider gap. Wide plank is a great look but it shows seasonal movement more than narrow strip does.
Is engineered hardwood better for Arkansas humidity?
It is more dimensionally stable, which is why we specify it for slab levels, basements, and walkout lower levels. On upper floors over joists, solid hardwood is usually the better long term choice because it can be sanded more times.
Talk to us. Heritage Hardwood Floors offers free in-home estimates across Northwest Arkansas. Call (479) 426-5337 or request an estimate.