How to Fill Gaps in Wood Flooring: Beginner Friendly Guide

Jan 14, 2024

If you have gaps between the boards of your wood floor, it can ruin the look of your floors and make them unsafe by creating tripping hazards. Thankfully, filling gaps in wood floors is an easy do-it-yourself project.

In this comprehensive guide from the floor sanding experts, you’ll learn several methods for filling gaps in wood floors. We’ll cover everything from buying the right supplies to prepping the floor to applying wood filler and staining for seamless repairs. With these tips, you can repair unsightly gaps in just an afternoon.

Why Do Gaps Occur in Wood Floors?

Before learning how to fill them, it helps to understand what causes gaps in wood flooring. There are a few common culprits:

Seasonal humidity changes – As wood absorbs and releases moisture, it naturally expands and contracts. During dry seasons, the boards shrink away from each other, leaving gaps.

Improper installation – If floorboards weren’t properly spaced during installation, gaps can pop up. Using subpar or uneven subflooring can also lead to gaps over time.

Structural issues – House settling, loose nails, uneven concrete below the flooring, and other structural problems can cause gaps between floorboards.

General wear and tear – Foot traffic, furniture rearrangement, pet claws, and everyday use slowly take a toll on wood floors, causing gaps and cracks between boards.

No matter the cause, unsightly gaps certainly detract from your beautiful hardwood floors. The good news is that fixing gaps in wood flooring is a relatively easy DIY project if you use the right materials and techniques.

Why Do Gaps Occur in Wood Floors

How to Fill Gaps in Wood Floors

Follow these steps to seamlessly fill gaps between boards in your solid or engineered hardwood floors.

Gather the Right Supplies

You probably have most of the supplies already on hand. Here’s what you’ll need:

Equipment / Tools

  • Tape measure
  • Table saw
  • Miter saw or handsaw
  • Hammer
  • Cloth
  • Sandpaper or planer
  • 5-in-1 tool or flathead screwdriver
  • Utility knife
  • Shop vacuum
  • Bucket
  • Putty knife


  • Wood floor boards or matching hardwood
  • Wood glue
  • Jute or cotton rope
  • Cardboard
  • Wood putty
  • Clear varnish or polyurethane

Before starting this project, it’s wise to set aside an afternoon or full day so you have enough time for the wood filler, putty, or caulking to cure completely. Rushing through the job may result in gaps reappearing later.

Step 1: Clean and Prep the Floor

Clean and Prep the Floor

First, remove all furniture, rugs, and debris from the area with gaps so you can access the entire floor. Sweep and mop the floors to remove dust, dirt, and grime so it doesn’t interfere with repairs.

Examine all gaps carefully. Use a tape measure to determine the width of each gap. Make notes so you know exactly how much new wood, filler, or caulk you’ll need to fill them.

Pay special attention to gaps wider than a 1⁄4 inch as these will require extra work to fill. You may need to cut and insert matching wood strips or apply multiple layers of filler.

Also, inspect for nails or staples that have come loose or popped up due to movement and seasonal changes. Use a hammer or pry bar to tap them back into place so they sit flush with the floorboards. Vacuum up any leftover debris.

Step 2: Fill Narrow Gaps with Rope and Glue

Fill Narrow Gaps with Rope and Glue

For minor gaps less than 1/8-inch wide, you can likely fill them using a simple rope and glue technique. This involves pressing cotton or jute rope into the crevices with wood glue to close small spaces.

Start by cutting lengths of rope slightly longer than each gap. Use a utility knife to split the rope lengthwise so it’s thinner. Spread wood glue onto the gap with a putty knife. Press the rope into the glue in the gap, leaving it just slightly overfilled.

Allow the glue to cure for 30-60 minutes. Then use sandpaper, a planer, or sharp knife to carefully scrape and smooth the rope completely flush with the surrounding boards.

Repeat this rope and glue method for every minor gap in your wood flooring. Be patient and meticulous for best results.

Step 3: Fill Larger Gaps with Matching Wood

Fill Larger Gaps with Matching Wood

For more pronounced gaps wider than 1⁄4”, you’ll need to cut and insert wood strips to reinforce the flooring before using filler. This provides extra stability so gaps don’t reappear later.

Start by measuring the exact width and depth of each large gap. Take precise measurements because even slightly imperfect wood inserts can still leave gaps or create new uneven spots across the floor.

Using a table saw, miter saw or handsaw, cut replacement wood strips to match the old flooring as closely as possible. Precision is key here for a seamless look. You may need to visit your local hardware store or wood shop to find boards that match your current floors.

Once your custom wood strips are cut, dry fit them by placing into the gap without any glue. Ensure they sit completely flush with no areas above or below the existing floor boards. Use a planer or sandpaper to carefully shape as needed.

When satisfied with the fit, run a thin bead of wood glue on the sides and bottom of the wood strips. Place them into gaps gently but firmly. Immediately use a damp cloth to wipe excess glue squeezed out from around the boards.

Allow the glue to fully cure overnight before moving on with other steps. The wood strips should now seamlessly fill the gaps.

Step 4: Apply Wood Filler and Shape

At this point, any minor imperfections around filled gaps can be smoothed with wood filler, which dries solid. Use a 5-in-1 tool or flathead screwdriver to scrape out gaps wider than 1⁄4”. Ensure you dig out any old glue or debris so it doesn’t interfere with new filler adhering.

Scoop some wood filler paste onto a putty knife and carefully press it into gaps and around wood inserts to create a seamless fill. Overfill slightly because the filler will shrink as it dries. Allow it to fully cure overnight.

Apply Wood Filler and ShapeOnce dried, the filler should have shrunk enough for you to shape it flush with surrounding boards. Use 60-100 grit sandpaper to carefully sand down excess dried filler until smooth and even with the rest of the floor.

Thoroughly vacuum dust and wipe clean. At this point, your gaps and cracks should be completely invisible, and you’re ready to stain and seal the repaired areas.

Step 5: Stain and Seal Repairs

With all gaps and imperfections now filled for an even floor, the last step is blending repairs for a uniform appearance. Tinting stains and clear finishes are key.

For natural hardwood floors, use a Q-tip to carefully apply small amounts of wood stain precisely over filler just until color matches flooring. Have a cloth and mineral spirits ready to quickly wipe up any excess and prevent staining adjacent boards.

Alternatively, use colored wood putty instead of regular filler, which avoids the extra staining step. After it cures, simply sand and seal.

Stain and Seal Repairs

For previously stained or finished wood floors, apply neutral clear wood filler so it blends after sealing. Once sanded smooth, apply one to two thin, even coats of clear varnish or polyurethane with a paintbrush over repairs and a few inches beyond. This seals and protects your floors while blending old and new areas for a uniform glossy appearance.

Allow sealants to fully cure 72 hours before placing furniture or regular foot traffic back onto floors.

Maintaining Hardwood Floors

While holes, cracks and gaps are easily repaired with enough patience and these steps, prevention is always preferable to preserve beautiful wood floors. Here are some handy tips to minimize wear:

  • Add felt pads to all furniture legs to prevent scuffing and scratches when moved
  • Arrange area rugs in high foot traffic zones to limit wear
  • Keep wood properly hydrated with humidifiers during dry seasons
  • Sweep regularly with soft bristle brooms (no vacuums!) to prevent gritty abrasion
  • Remove shoes when inside to avoid tracked-in dirt and pebbles
  • Clean up spills immediately to avoid stains and moisture damage
  • Avoid rolling chairs, carts, or appliances directly on the wood

When Should I Call A Professional For Flooring Repairs?

If you have extensive warping, cupping, loose boards, or major floor damage like flooding or pet stains, it’s best left to seasoned floor repair experts. Improper DIY fixes can make issues worse. Professionals have specialized tools and materials for flawless repairs.

For those with tricky wood floor repairs beyond your DIY comfort level, the technicians at offer complete installation, repair, refinishing, and restoration services.

Contact us for a free quote on renewing your floors today!

FAQs: Repairing Gaps in Wood Floors

What’s the best wood filler to use?

For small cracks and scratches, a water-based wood filler labeled for flooring is best. It’s easy to apply, dries solid, and sands smooth. Opt for one that matches your floor color.

For larger gaps or structural issues in floors, a two-part epoxy wood filler works well to firmly bond boards after replacing wood inserts. It dries harder than standard fillers.

How do I match the color of wood filler to my floors?

Carefully check filler colors against your floors in natural daylight before purchase. Or wait until after applying filler, then stain with regular wood stains, using a Q-tip for precision application only on the filler. Test colors on spare wood first.

You can also mix custom filler colors. Start with a neutral base and add small amounts of oil-based wood stain until achieving the desired shade.

What’s the best way to apply wood filler evenly?

Scoop a putty knife into filler and spread onto gaps with a smooth, even motion. Apply slightly more than needed since it will shrink. After curing, sandflush for a seamless appearance before staining or sealing.

Can I just use caulk instead of wood filler?

While acrylic caulks are convenient, they lack durability for the foot traffic floors receive. Stick with flexible, water-based wood fillers formulated specifically for floors for repairs that won’t crack or fall out later.

How long does wood filler need to cure before sanding or staining?

Check the wood filler instructions, but typically they need 6 to 12 hours of cure time before sanding or staining. Cool temperatures extend cure times. Ensure filler has hardened all the way through before finishing.

Why do some gaps reappear after filling and sealing?

If gaps didn’t receive backing wood strips before applying filler, they may flex and split filler. Also, if old glue or finish isn’t thoroughly scraped out before repairs, new filler won’t adhere right. Rushing drying times can also cause issues later.

How can I minimize seasonal gaps in wood flooring?

Keep relative humidity levels between 30-50% year-round. Get an HVAC system with humidity controls. Use several room humidifiers during winter months to prevent excessive shrinking. Also, allow space between walls and floor perimeter for expansion.

When should I call a professional for flooring repairs?

If you have extensive warping, cupping, loose boards, or major floor damage like flooding or pet stains, it’s best left to seasoned floor repair experts. Improper DIY fixes can make issues worse. Professionals have specialized tools and materials for flawless repairs.