How To Fill Gaps In Floorboards: 3 Ways To Seal Your Floors (UK) (2024)

Having a few gaps in your floorboards during the cooler months is very common. However, sometimes these gaps no longer close up when the weather gets warmer and more humid.

If you have constant gaping in your floorboards, you may want to consider filling them in.

A mix of dust and resin is an easy and cost-effective way to seal the gaps in your floorboards. However, adding wood strips of the same colour is more seamless and durable. Wood putty and filler are easier to apply but may not last as long as other methods.

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Why You Should Fill In Gaps In Your Floorboards

If there are gaps in your floorboards, you could be losing money on your home’s heating and cooling. The gaps are acting as holes through which air can escape.

They can also weaken the integrity of your whole floor. Filling in the gaps tightens the whole surface and prevents excessive movement of the boards.

However, gaps in floorboards are a normal part of having hardwood floors. Many times, you’ll only see the gaps in the winter because they close up in the more humid months.

If this is the case, you don’t need to worry about the gaps too much. It’s a natural factor in the expansion and contraction of the wood.

You should only need to fill these gaps when they no longer disappear in warmer weather. The following two methods will guide you through the entire process.

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How To Fill Floorboard Gaps – Wood Strip Method

Flooring professionals consider this to be one of the most effective methods for filling in floorboard gaps.

The process is a little longer and more expensive than other methods, but the results are the most reliable.

What You’ll Need

  • Tape measure
  • Table saw (optional)
  • Wood strips in the same colour or, ideally, the same flooring
  • Wood glue
  • Rubber mallet
  • Cleaning cloth
  • Electric sander
  • Wood stain/paint/finish (optional)

1. Measure The Exact Dimensions Of Your Gaps

Take precise measurements of the width and length of the gaps that need filling.

You want a tight fit so the pieces will stay in place for a long time to come.

2. Cut Wood Strips

Using a tale saw, cut strips of wood to the dimensions you need.

Ideally, you should always save a few planks of the original floorboards for future repairs such as this. However, a wood that’s close enough in colour will also work fine.

If you’re not comfortable using a table saw, check with your local hardware store. They may be able to cut the strips for you.

Or you can find strips that are the right width and cut them to the appropriate length. Table saws require precision, but cutting length is much easier than cutting width.

3. Apply Wood Glue And Hammer In The Strips

Apply wood glue to raw edges of your wood strips. Then, use a rubber mallet to wedge the strips carefully but firmly into the gaps.

Wipe up any excess wood glue with a damp cleaning cloth before it dries.

4. Let The Glue Dry, Then Sand The Floor

Following the manufacturer’s instructions is always a good idea. But a good rule of thumb for wood glue is to let it dry for about an hour.

Once the glue is dry, sand the floorboards where the gaps were to achieve an even surface. Re-stain or refinish the floor as necessary.

How To Fill Floorboard Gaps – Sawdust Method

Using sawdust is a common and inexpensive method to fill in floorboard gaps. However, it’s not the most effective, as the sawdust filler will shrink and shift over time.

If you decide to re-stain your floors, the colour of the filler may be noticeably different from the actual wood.

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What You’ll Need

  • Electric sander
  • Broom and dustpan
  • PVA glue or resin
  • Bowl
  • Paint mixing stick or wooden craft stick
  • Scraper or another flat tool
  • Cleaning cloth
  • Wood stain/paint/finish (optional)

1. Sand The Floorboards And Collect The Dust

Using an electric sander, sand down the areas of floor where there are gaps. Be careful not to spread the sawdust around too much, as you’ll need it for your filler mixture.

Sweep up as much sawdust as you can and put it aside – don’t throw it out.

2. Create A Filler Mixture With Glue Or Resin

PVA glue is a cheaper alternative to resin, but it’s not quite as durable. Whichever material you use, you’ll mix it with the sawdust in a bowl until it forms a paste.

A paint mixing stick or craft stick is great for this job.

3. Push The Paste Into The Gaps

Using a flat tool such as a paint scraper or even the mixing stick, push your dust mixture into the gaps of your floor. Fill in the gaps until the paste is level with the top of the floorboards.

You can use your scraper to level out the mixture. Then, carefully wipe away any excess from the surface of the floorboards with a damp cleaning cloth.

4. Let Dry And Sand Again

Let the dust mixture dry, then lightly sand the floorboards again to ensure you have an even surface. This time, you can sweep up and dispose of the sawdust from the sander.

If needed, re-stain or re-paint the floorboards.

How To Fill Floorboard Gaps – Wood Putty/Wood Filler Method

Wood putty and wood filler are two distinct products, but their application process is very similar. Both are very easy to use.

Note that wood putty is best for smaller, low-traffic areas. This is because it takes a long time to dry (if it dries at all). But it does a better job handling temperature change than wood filler.

You can apply wood filler to larger areas, and it will harden much faster than putty.

This also makes it more durable, but you may find it doesn’t last as long as other methods. This is because wood filler doesn’t handle fluctuating temperatures as well as putty or wood.

What You’ll Need

  • Wood putty or wood filler
  • Cleaning cloth
  • Electric sander (for wood filler)
  • Wood stain/paint/finish (optional)
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1. Sand The Floorboards (For Wood Filler)

If applying wood filler, use an electric sander to even out the floorboards where the gaps are.

If using wood putty, you don’t need to sand the floor first. Most wood putties are more effective on wood that already has a stain.

However, you should choose a putty colour that’s the closest match to your floorboards. This is because wood putty rarely absorbs stains.

2. Apply The Wood Filler Or Putty

Using a putty knife, press the putty or filler into the gaps according to the manufacturer’s instructions. If using filler, overfill the gap slightly as the material can shrink as it hardens.

With wood putty, simply ensure the putty reaches the top of the floorboard. Then, smooth it over with the putty knife so it’s level.

Clean up any excess putty or filler with a damp cleaning cloth.

3. Let The Filler Or Putty Dry

Assorted brands of wood filler could have different drying times. Always follow the manufacturer’s instructions to allow for enough drying time.

Putty can also have varying drying times, and some doesn’t fully dry at all. Some can take up to three days to dry, and it will still remain somewhat pliable.

4. Sand And Re-stain (For Wood Filler)

After the wood filler is dry, sand the floorboards for an even surface. Then, re-stain or repaint if you need to.


Floorboard gaps are a natural part of having hardwood floors. The wood contracts in the dry, cooler months, then expands in humidity.

If the gaps don’t disappear with the warm weather, they could cause your problems down the road. To prevent energy loss and a weak floor, you can fill in these gaps as they get worse.

Many professionals recommend using strips of wood cut to size and hammered into the gaps. However, it can be difficult and a little pricey.

If you want something a little more inexpensive, you can try filling the gaps with a mixture of sawdust and glue or resin.

Finally, for smaller gaps, wood putty or wood filler can do the job as well. These fixes are not as durable as the other two, but they’re very easy to apply

How To Fill Gaps In Floorboards: 3 Ways To Seal Your Floors (UK) (2024)


How To Fill Gaps In Floorboards: 3 Ways To Seal Your Floors (UK)? ›

If that doesn't resolve your problem, or if your gaps reappear, there are three main methods of filling gaps in wood flooring, which are: Using a dust and resin filling. Introducing filler strips. Inserting a colour-match acrylic filler.

What is the best way to fill gaps between floorboards? ›

Filling the gaps with strips of solid wood is considered to be the most effective and reliable method for filling wood flooring gaps. This method is frequently used on softwood or pine floorboards and we regularly use reclaimed pine strips to fill such gaps.

How do you get rid of gaps in floorboards? ›

Apply a fine bead of wood putty to the gap, then work it into the gap with your finger, using circular motions to force the putty down into the gap. Remove excess putty from the wood surface using a putty knife. Be careful not to scratch the floor's finish.

Should you fill floorboard gaps? ›

The even look of a gap-filled floor is pleasing to the eye but not always necessary. Filling gaps does stop draughts and prevents the build up of dust between the gaps. It also tightens the floor and helps prevent timber movement.

Can you seal between floorboards? ›

The easiest and most commonly used method for professional draught proofers to seal floorboard gaps is by using Fullers Ultraclear. This method has quite a few advantages including: Colour matching between caulk and floorboards is not required as Ultraclear is clear when it is dry.

What is the cheapest way to seal a floor? ›

Acrylics and epoxy topical sealants are the least expensive, but do require prep work. They aren't as durable and long-lasting as penetrating sealants.

Can I use caulk to fill gaps in floorboards? ›

Another option for filling gaps in wood floors is to use caulk. Caulk is a flexible sealant that can be used to fill small gaps and cracks. It comes in a variety of colors, so you can choose one that closely matches your flooring. To use caulk, simply apply it to the gap with a caulking gun.

Should you fill gaps in hardwood floors? ›

In our professional opinion, if your old wood floor has gaps, just live with them. They will look worse if you fill them and the wood filler cracks. Try to bring up the humidity in your home or wait for summer to come around to see them close up a bit.

Can you caulk between floorboards? ›

The easiest and most commonly used method for professional draught proofers to seal floorboard gaps is by using Fullers Ultraclear. This method has quite a few advantages including: Colour matching between caulk and floorboards is not required as Ultraclear is clear when it is dry.

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