Gaps in hardwood floors are one of the most common concerns we hear from Michigan homeowners. The good news: most hardwood floor gaps are normal, seasonal, and preventable. The bad news: some gaps indicate a real problem that needs professional attention. This guide helps you tell the difference and explains exactly what to do about each type.

Types of Hardwood Floor Gaps

Seasonal Gaps: Normal and Expected

Seasonal gapping is the most common type of hardwood floor gap in Michigan. It follows a predictable pattern:

• Winter (October–March): Gaps appear or widen as heating systems dry the air and wood shrinks
• Spring/Summer (April–September): Gaps close as humidity rises and wood expands

Seasonal gaps under 1/16" (about the width of a credit card edge) are completely normal. They indicate the floor is responding naturally to its environment — exactly as it should.

Solution: Maintain indoor humidity at 35–55% year-round with a whole-house humidifier. This dramatically reduces seasonal movement and keeps gaps minimal.

Permanent Gaps: May Need Attention

Permanent gaps — those that don't close in summer — indicate one of several problems:

• Inadequate acclimation: The floor was installed before it reached equilibrium moisture content. The wood dried out after installation and the gaps are permanent.
• Subfloor moisture problem: Moisture from below is causing the floor to cup or move unevenly.
• Improper installation: Fasteners spaced too far apart, insufficient expansion gaps, or other installation errors.
• Natural aging: Very old floors develop permanent gaps as the wood dries over decades. This is normal for floors over 50 years old.

Cupping with Gaps: Moisture Problem

If your floor has gaps AND the planks are cupped (edges higher than the center), you have a moisture problem — likely moisture coming from below. This requires professional diagnosis and repair. Do not attempt to fill cupped floors — the cupping must be resolved first.

How to Fix Hardwood Floor Gaps

For Seasonal Gaps

The fix is humidity management, not gap filling:

1. Install a whole-house humidifier on your furnace (the most effective solution)
2. Use portable humidifiers in rooms with hardwood floors
3. Target 40–45% relative humidity during heating season
4. Monitor with a hygrometer ($15–$30 at any hardware store)

Do not fill seasonal gaps with wood filler — the filler will be compressed and pushed out when the floor expands in summer, creating a worse problem.

For Small Permanent Gaps (Under 1/8")

Color-matched wood filler or rope filler can be used for small permanent gaps. Choose a filler that matches the floor's stain color. Apply with a putty knife, allow to dry, and sand flush. This is a cosmetic fix — it won't address the underlying cause.

For Large Permanent Gaps (Over 1/8")

Large permanent gaps require professional repair. Options include:

• Board replacement: Remove and replace the gapped boards with matching material
• Full refinish: Sand the floor, close gaps with a flexible filler, and refinish
• Re-installation: In severe cases, the floor may need to be removed and reinstalled after addressing the underlying moisture issue

Contact our floor refinishing service for professional gap repair in Michigan.

Preventing Gaps in New Installations

The best time to prevent gaps is before installation:

• Proper acclimation — 3–7 days minimum in the installation environment
• Verify subfloor moisture content before installation
• Install a whole-house humidifier before or immediately after installation
• Choose narrower planks (under 5") if your home has significant humidity swings
• Consider engineered hardwood for better dimensional stability

Frequently Asked Questions

Why do hardwood floors develop gaps in winter?

Heating systems dry the air, reducing indoor humidity. Wood shrinks as it loses moisture, creating gaps. This is normal seasonal behavior in Michigan. Maintain 35–55% humidity with a humidifier to minimize gapping.

Should I fill gaps in my hardwood floor?

Only fill permanent gaps — never fill seasonal gaps that open and close with the seasons. Filling seasonal gaps with rigid filler causes the filler to be pushed out when the floor expands, creating a worse problem.