Most hardwood owners notice it eventually: small gaps appear between boards in winter and disappear in summer.
It is normal. It is also manageable.
Table of Contents
- What Causes Winter Gaps in Hardwood
- Which Floors Show Gaps Most Visibly
- When Gaps Are Normal, and When They Are Not
- How to Reduce Winter Gaps
- Should You Fill Winter Gaps?
- When to Call Someone
- What to Expect From a Solid Floor in Ontario
- Related Guides
- Concerned About Gaps in Your Hardwood?
- Frequently Asked Questions
What Causes Winter Gaps in Hardwood
Hardwood is hygroscopic — it absorbs and releases moisture from the air around it, and it changes size as it does. Ontario winters typically pull indoor humidity below 30 percent without active humidification. The dry air pulls moisture out of the wood, the wood shrinks, and small gaps open between the boards. When humidity returns in spring the wood absorbs it back, expands, and the gaps close.
The wood lags the air by a few weeks, which is why the gaps peak in January through March and not on the first cold day. By April or May they narrow; by June most have closed entirely. This annual cycle is normal for solid hardwood. It is not a fault in the floor, a fault in the installation, or something a warranty is going to address — it is the material doing what the material does.
Which Floors Show Gaps Most Visibly
The same humidity swing produces very different-looking floors depending on what was installed:
- Solid hardwood shows the most seasonal movement. Engineered construction resists it, and many engineered floors show no visible gaps at all in mid-winter Ontario conditions.
- Wider planks show more. Each board has more wood to react, and the movement lands in a quarter as many joints. Plank width is a bigger factor here than most people expect at the point of choosing.
- Site-finished floors show more than prefinished. The finish flowed into the original tight seams, so when the boards shrink, the seam opens right at the surface.
- Floors over basements move more than floors on second storeys, because the humidity differential underneath them is larger.
When Gaps Are Normal, and When They Are Not
| What you are looking at | What it means | What to do |
|---|---|---|
| Small, uniform gaps that close in summer | Normal seasonal movement | Nothing |
| Gaps over 1/8 inch in mid-winter | Indoor humidity well below the 35 to 55 percent range | Humidity management |
| Gaps that do not close in summer | Boards have moved permanently, or something structural | Professional assessment |
| Gaps with cupping or crowning | Moisture-related damage, not dryness | Investigate before doing anything else |
| Gaps that appeared suddenly | A change in the house, not the season | Professional assessment |
The distinction that matters in that table is between dryness and moisture. Gaps come from the floor being too dry. Cupping and crowning come from moisture reaching the wood, usually from below. Seeing both at once means two different things are happening, and filling the gaps would address neither.
How to Reduce Winter Gaps
Everything that works here works by holding humidity up rather than by doing anything to the floor:
- Hold indoor humidity at 35 to 55 percent year-round. Everything below is a way of achieving this one thing.
- Run a whole-home humidifier integrated with the HVAC system. Room units help locally but a continuous floor moves as one thing.
- Avoid drastic temperature swings when the house is empty. Keeping it cooler with the humidifier still running beats letting it go dry over a two-week absence.
- Keep doors and windows shut through the coldest stretches, which is when every air exchange costs moisture.
- Monitor it. A hygrometer runs $20 to $40 and is the only way to know whether the humidifier is keeping up.
Done consistently, this keeps gaps small enough to be barely noticeable. It does not eliminate them, and any product that claims to eliminate seasonal movement in solid hardwood is describing something other than solid hardwood.
Should You Fill Winter Gaps?
Generally no, and this is the one place in the whole subject where doing nothing is actively the expert answer. Filling a seasonal gap creates a worse problem in summer: the boards expand into filler that has no give, and the filler compresses, pushes out, or lifts the boards. You have converted a gap that would have closed on its own into damage that will not.
Permanent gaps — the ones that do not close in summer — are a different case, and they can sometimes be filled as part of a refinishing project. That is work for a professional during refinishing, not a separate weekend fix.
When to Call Someone
Most seasonal gaps need no professional attention at all. Four situations do, and each of them can indicate a moisture or structural problem worth finding early:
- Gaps that do not close in summer.
- Gaps accompanied by cupping or crowning.
- Gaps wider than 1/8 inch in mid-winter despite active humidity management.
- Gaps that appeared suddenly, where there were none before.
What to Expect From a Solid Floor in Ontario
Solid hardwood will always show some seasonal movement in this climate. The realistic goal is keeping it small enough that you stop noticing, not eliminating it. Humidity management, narrower planks and engineered construction each reduce visible movement, and the three of them together reduce it a great deal.
If perfectly tight seams year-round genuinely matter to you — and for some people they do — then engineered is the more reliable choice and it is better said before the floor goes in than in February afterwards. Winter gapping is one item in the wider seasonal picture; caring for hardwood through an Ontario winter covers salt, grit and entryways, and the hardwood flooring guide for Ontario homes covers how humidity shapes every other hardwood decision.
Related Guides
A few other guides connected to this topic:
- Hardwood Flooring Guide for Ontario Homes (Solid, Engineered, Species, Finishes) — The complete hardwood pillar.
- How to Care for Hardwood Floors in Winter: Salt, Moisture & Humidity — Closely related topic in this category.
- Wide Plank vs Narrow Plank Hardwood: Style, Performance & Cost — Direct comparison with related materials.
- Hardwood Floor Maintenance Guide: How to Clean and Protect Hardwood Floors Over Time — Closely related topic in this category.
- Layering Rugs Over Hard Floors: How to Add Comfort, Style & Balance to Your Space — Design coordination guidance.
- Do Area Rugs Protect Hardwood Floors? How Rugs Prevent Scratches, Wear & Long-Term Damage — Closely related topic in this category.
- Flooring Installation Services — Our sell-and-install service — measuring, an itemized quote, and certified installation handled as part of your purchase.
- Why Work With Alexanian — A century of flooring and 17 Ontario showrooms behind every recommendation.
Concerned About Gaps in Your Hardwood?
The best way to choose what’s right for your home is to see the options side by side. Book an in-store appointment at one of our 17 Ontario showrooms and one of our consultants will walk you through what fits your space, your needs, and your budget – or request an in-home visit if that’s easier.
Frequently Asked Questions
Why do hardwood floors gap in winter?
Indoor humidity drops in winter, pulling moisture out of the wood. The wood shrinks, creating small gaps that close again in spring.
Are winter gaps in hardwood normal?
Small, uniform gaps that close in summer are normal seasonal movement. They are part of how solid hardwood lives in Ontario’s seasonal climate. Worry only if: gaps are very wide (over 1/8 inch in mid-winter), gaps do not close in summer, or gaps are accompanied by cupping or crowning—those signal humidity or moisture issues worth investigating.
Can I prevent gaps with a humidifier?
A whole-home humidifier maintaining 35 to 45 percent indoor humidity in winter typically reduces gaps significantly.
Does engineered hardwood gap less than solid?
Yes—the layered construction of engineered hardwood resists seasonal movement better than solid hardwood.
