Hardwood floors are built to last, but they’re also a natural product. Unlike synthetic flooring materials, wood responds to changes in temperature and humidity throughout the year. As indoor moisture levels rise and fall with the seasons, hardwood flooring naturally expands and contracts. This movement is normal, but if it becomes excessive, it can lead to gaps, cupping, crowning, or even buckling.
The good news is that most seasonal movement can be minimized with the right installation practices and a few simple maintenance habits. Here’s what causes hardwood floors to move and how you can help keep them looking their best year-round.
Why Do Hardwood Floors Expand and Contract?
Wood is hygroscopic, which means it absorbs and releases moisture from the surrounding air. When humidity increases, hardwood absorbs moisture and expands. When the air becomes dry, the wood releases moisture and contracts.
This is why you may notice:
- Small gaps between boards during dry weather
- Slight expansion during humid months
- Cupping if the bottom of the boards contains more moisture than the top
- Crowning if the top of the boards becomes wetter than the bottom
- Buckling in severe cases where excessive moisture has nowhere to go
A small amount of seasonal movement is expected. The goal isn’t to eliminate it completely. It’s to keep moisture changes within a healthy range so your flooring can perform as intended.
Maintain Indoor Humidity
The single most effective way to reduce seasonal movement is to maintain consistent indoor humidity throughout the year. For most hardwood flooring, an indoor relative humidity between 35% and 55% provides the best environment.
Depending on your climate, that may mean:
- Using a humidifier during dry winter months
- Running a dehumidifier during humid weather
- Letting your HVAC system help regulate indoor moisture
- Monitoring humidity with a simple hygrometer
Keeping humidity relatively stable helps minimize both shrinking and excessive expansion.
Keep Indoor Temperatures Consistent
Sudden swings in temperature can also affect indoor humidity levels. Rather than allowing your home to become extremely hot or cold, try to maintain a consistent temperature year-round. This creates a more stable environment for your hardwood flooring and helps reduce seasonal stress on the wood.
Improve Airflow Throughout Your Home
Good ventilation helps prevent excess moisture from building up indoors. Pay particular attention to areas where humidity tends to collect, including:
- Bathrooms
- Kitchens
- Laundry rooms
- Basements
- Crawl spaces
Use exhaust fans where appropriate and make sure crawl spaces are properly ventilated. Reducing excess moisture beneath your home can be just as important as controlling humidity inside your living space.
Protect Floors from Direct Sunlight
While moisture is the primary cause of seasonal movement, prolonged exposure to direct sunlight can heat sections of your floor unevenly. Over time, this may contribute to drying and color changes.
To help protect your hardwood floors:
- Close blinds or curtains during the hottest part of the day.
- Use UV-blocking window treatments when possible.
- Rearrange rugs and furniture occasionally so the floor ages more evenly.
One of the quickest ways to introduce unnecessary moisture is by using too much water during cleaning.
Clean Hardwood Floors the Right Way
One of the quickest ways to introduce unnecessary moisture is by using too much water during cleaning.
Instead:
- Sweep or vacuum regularly to remove dirt and debris.
- Use a microfiber mop with a hardwood floor cleaner.
- If using a damp mop, wring it out thoroughly so it’s only slightly damp – not wet.
- Wipe up spills immediately before moisture has a chance to soak into the wood.
Avoid steam mops or soaking the floor with water, as excessive moisture can contribute to cupping and other problems over time.
Proper Installation Makes a Difference
Even the highest-quality hardwood flooring needs to be installed correctly.
Before installation, hardwood flooring should be allowed to acclimate to the environment according to the manufacturer’s recommendations. This gives the wood time to adjust to the home’s temperature and humidity before it’s fastened in place.
It’s also important to:
- Verify that the subfloor has an acceptable moisture content.
- Leave the proper expansion gap around the perimeter of the room.
- Follow the recommended installation methods for the flooring being used.
Taking these steps helps reduce the risk of excessive movement after installation.
Is Seasonal Movement Normal?
Yes. In fact, a small amount of expansion and contraction is completely normal for hardwood flooring.
Minor gaps during dry weather or slight expansion during humid months don’t necessarily indicate a problem. However, large gaps, significant cupping, buckling, or sudden changes in the floor usually point to an underlying moisture issue that should be addressed before permanent damage occurs.
By maintaining consistent indoor humidity and following proper care practices, most homeowners can keep seasonal movement to a minimum.
Frequently Asked Questions
What causes hardwood floors to shrink?
Hardwood floors shrink when they lose moisture. This most often occurs during dry weather or when indoor heating lowers humidity levels.
Why do hardwood floors cup?
Cupping occurs when the bottom of a board contains more moisture than the top, causing the edges to rise. High humidity, moisture from below the floor, or water leaks are common causes.
What humidity level is best for hardwood floors?
Most hardwood flooring performs best when indoor relative humidity stays between 35% and 55%.
Can seasonal gaps in hardwood floors be prevented?
Small seasonal gaps are normal, but maintaining consistent humidity can greatly reduce their size and frequency.
Will cupped hardwood floors go back to normal?
If the moisture problem is corrected early, minor cupping often improves as the flooring dries and returns to a balanced moisture level. Severe or prolonged moisture exposure may require professional repairs.
Protect Your Hardwood Floors for Years to Come
Hardwood flooring is designed to move with seasonal changes, but excessive movement doesn’t have to be part of the equation. By controlling indoor humidity, following proper cleaning practices, and ensuring the floor is installed correctly, you can help your hardwood floors stay beautiful for decades.
Looking for premium hardwood flooring? Explore Advantage Lumber‘s selection of high-quality hardwood flooring and find the right species for your next project. Our team is also here to answer questions about installation, care, and long-term maintenance.