Hardwood floors are loved for their timeless look, warmth, and durability. But over time, even the best-laid wood flooring can start to show gaps between the boards. Whether it’s seasonal wood floor movement, shrinkage, or general wear and tear, filling those gaps can restore the look and integrity of your floors. This guide will walk you through how to fill gaps in hardwood floors the right way, using simple techniques and tools you likely already have.
Why Do Hardwood Floor Gaps Happen?
Before you grab your wood filler or putty knife, it’s important to understand the cause of these gaps. Hardwood floors naturally expand and contract with changes in humidity and temperature. In colder, drier months, floorboard shrinkage can lead to visible gaps. When the humidity returns, the boards expand again.
This natural wood movement is normal, but over time, persistent changes and poor maintenance can cause more permanent spacing. In older homes, you might see floorboards that have worn thin or moved out of alignment.
Is It Necessary to Fill Gaps in Wood Flooring?
If the gaps are small and seasonal, you might not need to do anything. But larger or permanent gaps can collect dust, make cleaning harder, or affect the structural stability of your flooring. Filling these gaps improves not just appearance but also longevity. Plus, it’s a straightforward DIY hardwood floor repair you can tackle over a weekend.
Tools and Materials You’ll Need
Here’s what to gather before you start:
- Wood floor gap filler (either flexible or solid, depending on gap size)
- Putty knife or flexible scraper
- Sandpaper (fine grit)
- Vacuum or broom
- Damp cloth
- Wood stain or finish (optional, to match existing colour)
- Masking tape (if staining nearby boards)
- Wood filler sticks or crack seal glue for deeper gaps
Step-by-Step Guide to Filling Gaps in Hardwood Floors
Step 1: Clean the Gaps
Start by cleaning out each gap thoroughly. Use a vacuum or broom to remove dust and debris. If dirt remains, it can prevent your filler from sticking properly. For narrow spaces, try using a thin tool like a flathead screwdriver wrapped in a cloth to clear everything out.
Step 2: Choose the Right Filler
Your choice of gap filler depends on the size and permanence of the gap:
- Wood filler is great for small to medium cracks and can be sanded and stained.
- Flexible gap fillers are ideal for areas with seasonal expansion and contraction.
- Rope or twine with wood glue works for larger gaps and is common in older floorboards.
- Ready-to-use crack seal glue like Davalba’s waterproof transparent sealant is great for deep gaps.
Make sure the colour of your filler matches your floorboards as closely as possible. Some brands offer tinted options, or you can mix in a matching wood stain.
Step 3: Apply the Filler
Use your putty knife to press the wood filler firmly into the gap. Overfill slightly to allow for shrinkage during drying. Smooth out the surface so it’s flush with the floor. Work in small sections, especially if you’re using a quick-drying product.
For hardwood floor crack repair that needs flexibility, silicone-based or elastic fillers are great for movement-prone areas.
Step 4: Let It Dry
Drying time varies by product. Wood fillers typically take a few hours, while flexible sealants may need up to 24 hours. Check the packaging for exact times and avoid walking on the filled areas during this period.
Step 5: Sand the Surface
Once completely dry, lightly sand the filled areas using fine-grit sandpaper. This ensures a smooth, level surface that blends into your original flooring. Always sand in the direction of the wood grain to avoid scratching.
Step 6: Touch Up with Stain or Finish
If needed, apply a wood stain to match your existing floor colour. Use a small brush and work carefully, especially if you’re only treating specific areas. For extra precision, apply masking tape to avoid overlapping onto neighbouring boards.
Finish with a hardwood floor finish or sealant to lock everything in and add shine.
Tips to Prevent Gaps in the Future
- Maintain consistent humidity: Use a humidifier in winter and a dehumidifier in summer to keep indoor levels steady.
- Inspect for seasonal changes: Some small gaps may reappear in winter but close naturally by summer.
- Recoat floors regularly: Proper hardwood floor maintenance, like recoating every few years, can reduce cracking.
- Avoid overwetting during cleaning: Too much water can damage floorboard alignment and speed up shrinkage.
What to Avoid When Filling Hardwood Floor Gaps
- Skipping surface prep: Filling over dust or wax won’t hold.
- Using caulk: Unless it’s a flexible, paintable caulk designed for wood, regular caulk won’t last.
- Filling moving gaps permanently: Don’t fill seasonal gaps with hard filler—it will crack when the boards expand.
Common Questions Answered
Can I fill gaps without sanding?
Yes, especially if you use a self-levelling filler or flexible option. But sanding provides the most seamless finish.
Should I wait for summer or winter to fix gaps?
It’s best to fill gaps when they’re at their widest—typically in winter. This way, they won’t crack when boards contract again.
What’s the best wood filler for floors?
Look for products specifically labelled as floorboard gap fillers. Guardsman’s wood filler sticks and Wudcare’s gap filler are excellent choices. They’re easy to apply, durable, and stainable.
Real Life Fix: A Quick Case
Last year, I helped a friend restore a 60-year-old wood floor in her London flat. We noticed multiple narrow and wide floorboard gaps. After vacuuming and cleaning, we applied a flexible wood filler in the living room and a crack seal glue in the bedroom, where the gaps were deeper. She followed up with a wood floor cleaner to finish the look. The whole process took two afternoons and completely changed the feel of the space—polished, neat, and way easier to maintain.
Final Thoughts
Filling gaps in hardwood floors might sound like a big job, but it’s surprisingly doable with the right tools and a bit of patience. Whether it’s a single crack or a whole room of misaligned boards, learning how to fill gaps in hardwood floors helps maintain both the beauty and functionality of your home. It’s a simple but effective part of long-term wood floor restoration and care.
A small effort today can save you from costly replacements tomorrow—and give your space a cleaner, more finished look that lasts for years.
