Few things change a floor's behavior as much as the seasons in the Upper Midwest. In January, heated indoor air can be very dry. In July, humid air comes through open windows. Basements stay cool and damp. Every flooring material reacts to these swings in its own way.
What happens through the year
Winter
Cold outdoor air holds very little moisture. When it's heated indoors, its relative humidity drops sharply. Homes without humidification can fall well below 30% relative humidity during cold snaps. Wood shrinks in dry air, so:
- Hardwood develops gaps between boards. This is normal seasonal movement in many homes; boards usually close up again in summer.
- Laminate and engineered floors are more stable but can still move.
- LVP doesn't respond much to humidity, but it does respond to temperature. Cold floors near drafty doors and big windows shrink slightly.
Very dry air can also cause static, dry skin and cracked wood furniture, which is why many homes run humidifiers in winter. Be careful: too much humidity in very cold weather causes condensation on windows and moisture problems in walls.
Spring
Snowmelt and spring rains raise outdoor humidity and groundwater. Basements may get damp or seep water. That's a good time to check grading, gutters and downspouts and to watch for basement moisture before installing flooring there.
Summer
Warm, humid air carries lots of moisture. Wood absorbs it and swells:
- Hardwood gaps close, and if conditions are extreme, boards can cup (edges higher than the middle).
- Floating floors expand and need their expansion gaps.
- Basements often reach high humidity, which can lead to musty odors and mold on organic materials.
Air conditioning and dehumidifiers help keep indoor humidity in check.
Fall
As heating starts, humidity drops again and wood begins to shrink. Fall is often a good time to install flooring because indoor conditions are moderate.
Ideal indoor conditions
Many wood flooring manufacturers recommend keeping indoor relative humidity roughly in the 30–50% range and temperature in normal living ranges year-round. LVP manufacturers specify temperature ranges and often warn against extreme heat from direct sun. Check your flooring's warranty for its specific requirements; some warranties require maintaining specified conditions.
A simple digital hygrometer, available at hardware stores, shows your home's humidity so you can adjust humidifiers and dehumidifiers.
Sun and heat
Large south and west windows can heat floors significantly, especially in the low winter sun. Some floating LVP products can expand, gap or peak in direct sun and heat; some manufacturers recommend window treatments or glue-down installation in sunrooms and areas with intense sun. See glue-down vs click.
Basements
Basement floors are concrete, below grade and often cool and damp. Before installing flooring in a basement:
- Fix any water infiltration and drainage problems first.
- Test slab moisture with an accepted method; see moisture testing.
- Choose a floor suitable for below-grade installation, often LVP or tile.
- Use the vapor barrier or moisture mitigation the manufacturer requires.
- Run a dehumidifier in humid months to keep humidity in a healthy range.
Seasonal paint effects
Humidity affects painting too. Interior latex paint dries more slowly in humid summer conditions, and bathrooms need extra time and ventilation for paint to cure. In winter, cold exterior walls and windowsills can be too cold for paint to cure properly if a room isn't heated. For exteriors, see exterior painting in western Wisconsin.
The takeaway
The best thing you can do for any floor is keep indoor conditions reasonably steady year-round, install when the home is at normal living conditions, and follow the manufacturer's acclimation and expansion requirements. Read flooring acclimation for how that works.