Are Gaps in Hardwood Floors Normal? 7 Ways to Fix Them

Hardwood flooring is one of the most popular options used for flooring in homes and apartments. It is ageless, and not only does it enhances the look of your home, but it also adds value to it. However, hardwood floors also come with their own set of problems as well. One of which is the occasional development of gaps and cracks in between floorboards.

Hardwood floor gaps and cracks can range from hairline widths to the thickness of a quarter. Having seen how beautiful it looks in perfect condition, you may be wondering, are gaps in hardwood floors normal?

Generally speaking, gaps and cracks in hardwood floors can happen normally in a year. Floorboards separate when the air is drier and when the hardwood loses its moisture content but close back up again when it becomes more humid. The wider the floorboard is, the wider the gap is expected as well.

In normal conditions, seasonal gaps in the hardwood floors will happen in a year but you should expect them to close back up again when humidity levels rise up, usually in the summertime when it’s more humid. If the gaps persist and do not close back up, this is considered an abnormal condition and should be investigated.

It would be best to know the real cause of the gapping before you decide what to do next. In most cases, the gapping problem is minor and can easily be fixed by you. Unnaturally large gaps between the floorboards may mean something more serious though and it is recommended for you to call a professional contractor to help you find the underlying problem and fix the wood floor properly.

Should There Be Gaps in Hardwood Floor?

A lot of homeowners are concerned when they see gaps appearing in their hardwood floors or that their floorboards seem to be separating. But should they be worried, and is it normal to have gaps in hardwood flooring? Seasonal gapping or separation of floorboards usually happen in hardwood floors and you’ll usually notice this happening during winter or when the air outside is dry and cold. And in most cases, you’ll find that these gaps close back up again during the hot season, or when the air outside is hot and humid.

Hardwood floors, just like any wood, are hygroscopic materials. This means that they absorb moisture either through liquids they get into contact with or through the moisture contained in the air. Hardwood floors tend to expand when they absorb more moisture and contract when they release it.

It normally adapts and balances itself to the current conditions of its environment. So when the air is more humid, usually in the summer, the wood floor carries more moisture in it and will tend to become wider. This is in contrast to when the air is dry and less humid, for example during the winter, the wood floor will have less moisture in it and will grow smaller. You’ll notice the gaps and the floorboards separating during winter or when the hardwood floor is carrying less moisture.

What Are Acceptable Gaps in Hardwood Floors?

Gap width and thickness will vary depending on a number of things. Although the humidity levels play a major part in how wide the gaps and cracks become, there are a few more factors that affect how much the hardwood floor will shrink and gap.

Some wood species for example are more dimensionally stable than others. This means that some floorboards don’t expand or contract as much as other species do. Like for example, maple and hickory hardwood floors are said to show bigger gaps more than oak or pine wood floors when observed under the same conditions.

The type of cut the wood floors were made from also contributes to how they will expand and contract over time. Different cuts reveal different grain patterns and how the grain patterns are arranged will expand and contract differently from others. Plain sawn or flat sawn wood displays a cathedral pattern on the face of the wood while the rift and quarter sawn wood display a straight grain pattern.

Plain sawn or flat sawn wood tends to expand and contract along the sides of the board while the rift and quarter sawn floorboards expand and contract vertically. This makes the plain sawn wood develop gaps more than the rift and quarter sawn wood. So a rift and quarter sawn wood floors are considered more dimensionally stable than plain sawn wood.

Wider floorboards also tend to expand and shrink more than smaller and skinner boards. This means that the wider floorboards will gap more than smaller floorboards. So under the same conditions, a 5″ wide floorboard will shrink twice as much as a 2-1/4″ wide plank.

It is normal and acceptable for a hardwood floor that is 2-1/4″ wide to have a gap of 1/32″ thickness and the same wood species that is 5″ wide to have a gap of 5/8″ thickness. Acceptable gaps can range from 1%-5% of the hardwood floor’s width depending on the conditions of its environment, the wood species that was used, and the type of cut that the floorboards were made from.

Should There Be Gaps in New Hardwood Floor?

A newly installed hardwood floor should have its floorboard closely fitted against each other and should not reveal any gaps, assuming that the installation was done correctly. If you are doing the installation of the hardwood floors yourself, you should not leave gaps in between floorboards. Depending on the type of hardwood floor you are installing, an expansion gap may be needed around the perimeter of the floor but not in between the floorboards themselves.

If a newly installed hardwood floor is showing gaps in between floorboards or is separating unnaturally, it is most probably caused by improper and poor installation. You should have it checked by a professional floor contractor if this is your floor’s situation.

There is a proper way of installing hardwood floors and it involves a couple of steps. It includes the proper acclimation of the hardwood floors to allow it to adjust and adapt to its environment which can help minimize the gap thickness it produces in the future as well.

Here’s a short video by Build Direct briefly explaining hardwood floor gaps.

Not all hardwood floor gaps are normal though, and some may need urgent actions to fix it. If the gaps do not close back up or the gaps are becoming unusually larger than before, then you may have a different problem you might need to resolve. In any wood flooring gapping problem, you should first identify the possible reasons why it is happening so that you will know the possible solutions to address the situation properly.

7 Possible Reasons Why Your Hardwood Floors Are Separating

Hardwood floors will normally gap during a dry season and should close back up again during a humid season. The cycle of floorboards separating and coming back together again in a year’s time is to be expected and part of a hardwood floor’s life.

If you notice that gaps in your floorboards are not closing up, are getting unnaturally bigger, or the gapping problem spreading across the entire hardwood floor, then it can be considered something abnormal and should be investigated. Below are 7 possible reasons why your hardwood floors are separating or gapping.

1. Failure to Acclimate Hardwood Floorboards Properly Before Installation

One of the most important steps that have to be done prior to the installation of the hardwood floorboards is to acclimate it properly in the area it will be installed on. Acclimation is a process wherein the hardwood floorboards are placed and stored inside the room where they will be installed on.

The floorboards are left there for a few days with the room’s ventilation system allowed to continuously run to mimic the room’s normal micro-climate conditions on most days of the year. This will allow the hardwood floorboards to adapt and be in equilibrium with the moisture and humidity levels of the room’s normal conditions.

Allowing the hardwood floorboards to adjust and adapt to the normal conditions of the room will minimize the possibility of any hardwood floor problems caused by humidity and moisture levels in the future. This includes gapping, cracking, and floorboards that are separating.

If the hardwood floorboards were not acclimated properly before installation, they may have moisture levels that do not match the normal moisture levels of the room. Hardwood floorboards that have a high moisture level during installation will be a bit wider than if they were acclimated properly. Once the hardwood floorboards are installed, and they start adapting to the normal conditions of the room, they will release some of the excess moisture they have and will slowly contract. This will result in unnecessary floorboard gaps in the future that will not be closing back up.

2. Hardwood Floors Were Installed in an Unnaturally High Humid Condition

When installing a hardwood floor, it is ideal to pick a day where humidity levels are considered to be the average for a year. It will be easier to set the room’s normal micro-climate conditions when you acclimate the hardwood floorboards inside that way. Also, during the installation of the floorboards, the humidity and moisture levels of the room should also be maintained constantly with ventilation or HVAC systems so as not to allow the floorboards to expand or contract unnecessarily.

If the hardwood floorboards’ environment has an unnaturally high humid level during installation, the wood floorboards will be carrying excess moisture and will be wider than normal. When the room’s humidity and moisture levels lower down to their average levels, the floorboards will also release some of their moisture content to adjust along with the room. This will cause gaps to appear in between floorboards as they contract and may not be closing back up again.

3. Incorrect Nail Spacing Was Applied When Hardwood Flooring Was Installed

Hardwood floorboards are normally nailed to the subfloor or to the floor joists. There’s a recommended nail pattern and spacing to be followed when fixing the hardwood floorboards to the subfloor or floor joists. An incorrect nail spacing pattern can cause problems to the hardwood floor in the future. For instance, fewer nails used may cause bigger gaps in your hardwood floor, while too many nails used may cause splitting in the floorboards.

Always follow the manufacturer’s nail spacing standards and recommendations to avoid these problems in the future.

4. Hardwood Floorboards Were Installed Improperly

Once the hardwood floorboards have properly acclimated and the room’s normal micro-climate conditions have been set and are being maintained during installation, the next thing to do is to start the installation of the floorboards. The floorboards should be fitted well to each other, making sure that it’s a snug fit. All the boards should also line up and perfectly straight starting from the first board up to the end.

If the floorboards were not fitted well to each other, and if some boards were not installed perfectly straight, they will most likely separate over time which will cause the gaps to eventually appear. Generally speaking, an improperly installed hardwood floor will cause a lot of different issues in the future, including gapping and floorboard separation.

5. Extreme Indoor Humidity Changes Beyond The Ideal Levels

Relative humidity (RH) is the measure in percentage of the amount of water vapor in the air. Basically, it is a measure of the humidity level of a space. The ideal RH level indoors is between 30 – 50%, at a temperature of 60 – 80 degrees Fahrenheit. These values are also considered to give good thermal comfort to humans which is why it is also the values that are followed when setting a room’s normal micro-climate conditions when installing and maintaining hardwood floors.

Extreme humidity and moisture level changes indoors can affect the amount of moisture that is in the hardwood floorboards. When RH level reaches numbers below 30% or above 50%, hardwood floorboards tend to dry up or absorb more moisture which leads them to either contracting below or expanding above their ideal range. These extreme changes in humidity will cause gapping issues between your hardwood floorboards.

These issues normally happen in winter when the room gets exposed from the outside air temporarily from an open door or window, lowering down the RH level of the room. The cool and dry air from the outside will suck moisture from the hardwood floorboards, while your heating ventilation indoors will further dry them up. These will cause the boards to contract and develop gaps and cracks.

You can purchase a hygrometer from Amazon which is a good way to keep track of the relative humidity and temperature of your home.

6. Hardwood Floorboards Are Located Too Close to a Heating Vent or a Fireplace

If hardwood floorboards were installed too close to a heating vent or a fireplace, it can cause them to over-dry. Setting the HVAC systems to a high heating level, usually during winter, can also cause the relative humidity (RH) levels of the room to go lower. This will also cause the floorboards to over-dry. Over-drying the hardwood floorboards can lead them to contract and shrink, and gaps and cracks in between boards will start to develop.

7. Structural or House Foundation Settlement Issues

If your home’s structural footing or foundation starts to settle, the walls, columns, supports, and beams move. The area of your hardwood floor may move and stretch as well which will affect the joints of your floorboards. These structural movements will result in the development of gaps in your hardwood flooring.

Structural settlement issues should be addressed at once because it will not only affect your hardwood flooring, it will affect the whole house in general as well.

7 Ways to Fix the Gaps and Cracks in Hardwood Floors

Identifying the underlying cause of the problem is the first step to knowing what to do with the gaps in your hardwood flooring. After identifying the cause of your hardwood floor gaps and floorboard separation, you will then be able to make decisions as to how to address the problem better.

Not all hardwood floor gaps need fixing. If your hardwood floors are experiencing seasonal gaps, meaning if the gaps do close back up again during the more humid season, this is considered normal and you don’t need to do anything else. Just let your hardwood floors expand and contract normally as they would but make sure to clean or vacuum the gaps every now and then to remove any dirt or debris that may have fallen in the gaps.

It is important to understand though that most of the time, the cause of the unnatural or abnormal development of gaps and cracks in your hardwood floors is from the improper installation of the flooring. The ideal solution to this usually is for you to replace or reinstall the whole floor. This of course will be costly and may not be practical for most people. So some of the solutions listed below may only be temporary and some are alternative fixes. This may not be as good as replacing the whole floor but it will be a lot cheaper and it will still work to fill in the gaps and improve the look of your hardwood floor.

If your hardwood floors are experiencing seasonal gapping, and the gaps do close back up normally during the humid seasons, understand that filling in the gap using any filling material is not recommended. Any filling material applied or inserted in the gaps will be forced out when the gaps close up, and your floor might look worse than if you didn’t apply any filling material. Also, if the filling material will not allow the floorboard gaps to close normally, it may cause cupping on your hardwood flooring.

Below is a list of 7 ways to fix the gaps and cracks in your hardwood flooring.

1. Use a Humidifier to Manage the Relative Humidity of Your Home

Most of the time, the cause for hardwood floorboard gaps is the drop in the relative humidity of its environment. This causes the floorboards to release moisture which makes them contract or shrink and leads to gapping. This can happen during seasonal changes, like in the winter.

Ventilation and heating systems can also over-drying your floorboards, sucking out moisture from them, which can also lead to their contraction and gaps appearing in your hardwood flooring.

Whatever the reason why the moisture content of your floorboards is decreasing, you can try using a humidifier to add moisture to the air. This will help maintain the moisture content of the floorboards and prevent them from shrinking and separating from one another. As long as you maintain an RH level above 35%, the floorboards will not shrink, and gaps will not develop.

Just make sure that the RH level doesn’t go beyond 55%, otherwise, your floorboards might expand too much and may cause cupping issues in your hardwood flooring.

Humidity controls can actually be installed with your HVAC systems to control the RH levels of your homes. If there is no HVAC system installed in your home, you can always get a good humidifier from Amazon. Also, you might need a hygrometer to track the current RH level as well.

2. Fill the Hardwood Floor Gaps With Wood Putty

For hardwood floor gaps that are not closing back up as they should normally, you could decide on filling the gaps with wood putty. Just make sure that you are actually using wood putty and not wood filler. Both are different products in that a wood putty will still be a bit elastic after drying up while wood filler will become hard. Also, wood fillers can only be used on unfinished hardwood floors while wood putty can be used to fill gaps on finished wood floors, especially on prefinished hardwood floors.

Your wood floors will still expand and contract over time, at the same time, the gaps in between floorboards will expand and contract as well. You would want something flexible to fill in the gap that can adapt to those changes. Wood putty, retaining its flexibility after it has dried, would be a good material to use to fill the gap.

For this method, you would need a wood putty, which you can buy from Amazon. Choose a wood putty with a tone close to the stain or color of your wood floor. You’ll also need cloth for cleaning, and a putty knife.

Steps on How to Fill Hardwood Floor Gaps With Wood Putty

  1. Clean the gap off dirt and debris using vacuum or your putty knife. Also, clean the edges of the floorboards on both side of the gaps with a slightly damp cloth. Cleaning the gap and the surfaces of the floorboards will ensure a good adhesion of the wood putty.
  2. Using a small amount at a time, apply wood putty to the gap. Working your way slowly along the length of the gap, using your finger, using circular motions, pushing the putty inside the gap. Remove any excess wood putty from the floorboard’s surface using the putty knife but be careful not to scratch the board.
  3. Let the putty dry for at least 24 hours before walking on the floor. Wipe the floorboards clean of any wood putty residue using a damp cloth.

3. Fill The Hardwood Floor Gaps With Sawdust

Similar to wood putty above, filling gaps in floorboards with sawdust and wood glue, such as PVA or polyurethane, creates an elastic gap filler that will adapt to the changes as the wood floor gaps expand or contract.

You would need sawdust for this fix preferably of the same wood species as your hardwood flooring. You might have collected sawdust from your sanding pad or miter saw that you could use. You’ll also need wood glue, and wood finish or wood stain that is similar to what is used on your hardwood floor. You’ll also need a cleaning cloth, and a putty knife as well.

Steps on How to Fill Gaps in Floorboards With Sawdust

  1. Clean the gaps off dirt or debris using vacuum or the putty knife. You can also wipe off the surface using a slightly damp cloth. This will ensure that the sawdust paste you shall be applying will adhere well to the floorboards.
  2. Create your sawdust filler in small amounts at a time, at most around 2 tablespoons of sawdust in one mix. This is because the paste dries up fast and you would need to apply it quickly to your gaps as soon as you’ve have the mix. To create the sawdust filler, mix around 2 tablespoons of sawdust with your wood stain color, and then apply some wood glue to the mix. Mix everything well until you get a consistent colored paste.
  3. Apply the sawdust filler quickly to the gaps, using the putty knife to push in the mixture.
  4. Allow the paste to dry, this will be about 10 mins.
  5. Apply additional finish or wood marker if you still need to closely match the color of the filled gaps to your hardwood floor.

You can watch a short demonstration below on how this is done.

4. Fill The Hardwood Floor Gaps With Wood Strips

For wider floorboard gaps, you can use wood strips to fill the gaps. This is also a great fix and method for restoring old hardwood floors and filling gaps between old wooden floorboards. It is best to do this method when the weather is at the most humid and the gaps are at their smallest. This will prevent the hardwood floors from cupping when it tries to expand.

For this method, you would need spare floorboards of the same wood species as your hardwood flooring or simply use pieces of matching hardwood lumber. Just understand that this method will require you to sand and refinish the whole floor after you’ve inserted the wood strips into the floor gaps.

You’ll also need the following equipment and materials:

Steps on How to Fill Gaps With Wood Strips

  1. Using the tape measure, measure the widths and lengths of each of the gaps in your hardwood floor.
  2. Using a table saw, rip-cut saw the spare floorboards to the measured widths of the gaps.
  3. Using a mitre saw or handsaw, cut the wood strips to the lengths of the floor gaps it would fill in.
  4. Apply wood glue to the sides of the wood strip. Insert it inside the gap and tap it genly with a hammer or mallet until it is completely inside. Wipe off any excess wood glue from the surface of the hardwood flooring.
  5. Using sand paper and planer, trim off any high points off the wood strips.
  6. You can then sand and finish the whole floor normally.

Watch a video below, explaining how this process can be done.

5. Fill The Hardwood Floor Gaps With Rope

This is another good method of filling large gaps in hardwood floors. Similar to using wood strips to fill gaps, this method can also be used for restoring old hardwood floors to fill gaps between old wooden floorboards.

For this method, make sure you’re using a natural fiber rope such as jute or cotton. Since we will be staining the rope to match the color of the hardwood floor, a natural fiber rope will be able to accept the stain while a synthetic rope cannot.

You’ll need the following tools and materials:

Steps in How to Fill Floorboard Gaps With Rope

  1. Clean the gaps and remove any dirt and debris using the vacuum. You can also use the 5-in-1 painter’s tool to scrape off any old putty or adhesive that may be sticking loose in the gaps. Make sure the gaps are completely clean.
  2. The rope that you should be using should have its diameter slightly bigger than the gap. In a bucket, pour the wood stain that matches the stain of your hardwood floor. Dip the rope inside the bucket until it gets saturated by the wood stain.
  3. Remove the rope carefully from the bucket and slowly stretch it on a clean carboard to let it dry. Don’t expose it though to direct sunlight or any heat as some wood stains are flammable and the rope could spontaneously ignite.
  4. Using the 5-in-1 painter’s tool or putty knife, force the rope inside the gaps. Push it in until the rope is flush with the floor. Trim any excess rope using the utility knife. You can also use glue to secure the rope to the floorboard gaps.
  5. Once the rope is secure, you can apply a clear varnish or urethane to the rope to give it a hardened surface.
  6. Clean the area as necessary with a cleaning cloth.

Watch the video below to give you an idea of how this method is done.

6. Slide the Floating Floorboards Back Into Place Using Suction Cups and a Mallet

If you’re using a floating hardwood floor, or if your flooring is not nailed to the subfloor, you can just slide your floorboards back to their places. This is just an easy fix for floating floors with gaps or that have floorboards separating as you’ll only need a glass suction cup and a mallet.

All you need to do is to stick the glass suction cups to the affected floorboard, or the floorboard you want to slide back into place, and then using the mallet, carefully strike the suction cup in the direction where you want the floorboard to slide.

Watch the video below demonstrating how this is done.

7. Replace the Whole Floor

If you have the budget, and the hardwood floor has too many gaps and is damaged to be repaired easily, it may be best to just replace the whole floor entirely. This is especially true if the underlying cause of the hardwood floor gaps is the structural or foundation settlement of your house.

If the gapping was caused by structural issues, you need to resolve this first before repairing your hardwood floor.

7 Tips on How to Prevent and Minimize Gaps in Hardwood Floors

Prevention is better than the cure as they say and with regards to hardwood floors, there are steps you can take to prevent or minimize the gaps from developing in the future. You can’t actually totally prevent gaps from happening in your hardwood floors since it’s a normal occurrence with changes in the weather. You can, however, minimize, or at least maintain a thin small gap when it develops to your hardwood floors.

Below are 7 tips on how to prevent and minimize hardwood floors from separating and developing gaps in the future.

1. Acclimate the Hardwood Floorboards Prior to Installation

The proper acclimation of your hardwood floorboards prior to installation is crucial to avoid any sudden changes to their dimensions once they are already installed. This includes the development of gaps and floorboards that are separating from each other. Acclimation is the process of making balancing out the moisture content of the floorboards to the humidity levels of the room. It is important, when acclimating the floorboards, that the heating and ventilation systems of the room are turned on to match the room’s normal micro-climate conditions when being used normally.

2. Make Sure the Hardwood Floorboards Are Installed Properly

Proper installation of the hardwood floorboards is important. Make sure all hardwood floorboards are aligned straight. All the floorboards should also be fitted together snugly. Keeping everything closely fitted will help minimize gapping in your hardwood floors in the future.

3. Regulate and Maintain the Proper Humidity Inside Your Homes

Once the hardwood floorboards are installed, the moisture and humidity levels of your homes, or wherever the hardwood flooring is installed, to be maintained and regulated at a certain range. The recommended RH levels are between 35%-55% and room temperature between 60 – 80 deg Fahrenheit. You can use a humidifier or install an HVAC system with humidity controls to regulate the RH levels.

Also, during winter or the cold season, since the air is going to be drier outside, make sure that all your windows and doors are sealed. You want to avoid your hardwood flooring be exposed to the dry air outside, which can suck moisture out of it.

The consistent and acceptable humidity and moisture levels in your home will prevent or minimize gaps from developing in your hardwood floors in the future.

4. Opt for More Dimensionally Stable Wood Species for Your Hardwood Floorboards

Some wood species are more dimensionally stable than other wood species. This means that some wood species expand and shrink more than others, which also means that hardwood floors of those species can gap or cup more than others. Maple and hickory expand and contract more than oak or pine. If you have a choice, go for the more dimensionally stable oak or pine wood for your hardwood flooring. This can minimize or prevent gaps and floorboard separation from developing in the future.

5. Opt for More Dimensionally Type of Wood Cuts for Your Hardwood Floorboards

The type of cut used for your floorboards will affect how they will expand or contract to humidity and moisture changes in the air. A plain sawn or flat sawn wood floorboard expands and contracts sideways while a rift and quarter sawn floorboard expands and contracts vertically. This means that a plain sawn floorboard will most likely develop gaps more than a rift or quarter sawn floorboard.

Using a rift or quarter-sawn floorboard for your hardwood flooring will minimize and help prevent gaps to develop in the future.

6. Opt for Slimmer or Skinnier Hardwood Floorboards

The wider the floorboard, the bigger the expansion and contraction, and the bigger the gaps that can develop. So using a slimmer and thinner hardwood floorboard will develop thinner gaps while using a wider floorboard will develop thicker gaps.

If you can, go for the slimmer or skinner hardwood floorboards for your hardwood flooring to prevent gaps from appearing, or at least maintain a minimum gap thickness in your flooring.

7. Opt for Engineered Hardwood Flooring Rather Than Solid Hardwood Flooring

Engineered hardwood flooring is more dimensionally stable than solid hardwood floors. Even with extreme changes in humidity, engineered hardwood flooring can resist expansion and contraction more than solid hardwood flooring. If you can opt for engineered hardwood flooring instead of solid hardwood flooring. They have a better chance of not getting any gaps in the future.


He is an architect for more than 20 years. He is passionate about design and architecture and enjoys sharing his knowledge and information with people as well.

Recent Posts