What Are Wood Floor Gaps and How to Fix Them

What Are Wood Floor Gaps and How to Fix Them

If you have wood floors, do you ever see gaps between the boards? Usually, they are more noticeable at certain times of the year. They can trap dirt and dust besides affecting the beauty of your hardwood floor like a gap-toothed smile.

Wood floors “breathe,” expanding and contracting due to changes in humidity. Seasonal wood floor gaps are a typical phenomenon, but you can reduce the effects with proper humidity control. 

If there are wider wood gaps that don’t close, you’ve come to the right place. We’ll give you a few pro-tips on how to fill in the gaps and make your floor look great again.

Why Do We Have Gaps in Our Wood Floor?

A gap between boards in wood floors the thickness of a dime is not uncommon, especially in older homes. The width of a dime is 3/64th inches or about 1.1-1.2mm thick. 

If you can sink a dime into the gap between boards, it may be a natural contraction, but it still doesn’t look right. 

There are a few reasons that it happens:

  1. Not acclimating the boards – When first installed, the boards will be tight and smooth. However, installing the wood before it has a chance to acclimate to the surroundings will cause the wood to shrink and create gaps. 
  2. Poor Installation – If the boards were installed carelessly and not tight with the other planks, there would be spaces. Also, poor craftsmanship can result in unsightly gaps around outside corners that become worse as the room becomes less humid.
  3. Ununiform planks – Boards of random size, thickness, or that don’t have a straight edge can also create this problem. 

Of these three, moisture and humidity are the leading cause. When the boards dry out, they shrink away from each other, creating unsightly spaces. They tend to appear during the first winter after being installed.

However, for some hardwoods, it may take many years before they become noticeable. It doesn’t mean you must replace the floor. It means you need to add more humidity so that the planks can retain their shape. Think grape vs. a raisin. 

We’ll cover the remedies in just a bit.

Conditions That Contribute to Gaps in Hardwood Floors

Fluctuations in humidity are the primary cause of gapping. If the floor were installed during the summer months, you could see shrinking during the drier, heating season of winter. We mentioned dime-sized gaps earlier. Typically, these will swell closed again in the spring and summer months.

Ideally, you’ll want to keep the humidity level in the home between 35% to 45% and temperatures between 60°F to 80°F (15.5°C to 26.6°C). That’s not always easy. 

Humidity levels range from 18% in the desert southwest of the U.S. to as much as 90% in the muggy southeast. In the chilly north, where people tend to use fireplaces and woodstoves, the humidity can be as low as the desert. One clue that your home is dry is getting static shocks when touching a doorknob. 

For additional information about humidity, check out this excellent article, “Comfortable Humidity Levels for Your Home and Hardwood Floors.”

Ductwork located under the floor can be another problem, drying out the wood. Adding a deflector to vent the air upward will help. 

However, if the cause of the gaps is a result of poor nail or clip spacing or subfloor issues, you’ll need a more permanent solution. 

Before we touch on this matter, let’s go over the things that you can do to minimize wood floor gaps.

Avoiding Hardwood Floor Gaps

If you are installing a new wood floor, you can prevent shrinkage and spaces from happening later by taking some precautions upfront. 

First, acclimate the new flooring in your home. To do that, unwrap the planks or open the ends of all the boxes. Then cross-stack them in the room in which you plan to install. Leave space between the boxes or planks to allow for airflow. Leave the planks this way for seven to ten days or more. Loose stacking will enable the wood to match the temperature and humidity of the space. 

Even if you are using reclaimed wood, you still need to acclimate it to your home’s environment. Otherwise, you risk warping or gapping if there is a significant variance in the humidity or temperature.

Humidify During the Cold, Dry Months

If your home tends to be dry due to the climate or heating, you need to add humidity. Some of the ways to do this are:

  • Keep a full kettle of water on top of your wood stove 
  • Use a portable humidifier in the room
  • Add a furnace humidifier if possible

Dehumidify During the Damp Months

If you have high humidity issues, such as wet basements or prolonged rainy seasons, use a dehumidifier. High humidity will cause cupping and crowning, but a dehumidifier will prevent that from happening.

Whether adding or decreasing moisture, it’s best to purchase a digital hygrometer to measure the relative humidity. Remember, you are looking for relative humidity between 30% to 45%.

If you tackle the humidity problems and you still experience gaps, here’s what you can do.

Helpful Tips How to Fill in Wood Floor Gaps

If the gaps in your floor are not closing between April and October, then it’s time to call a flooring professional. It’s the best time of year to fix gaps because it tends to be more humid.

Want to try it yourself? Here are some professional flooring tips.

Filling Narrow Gaps

Remember, if the gaps are seasonal and close back by themselves, you don’t want to add a filler. It will just squeeze out, making a big mess. 

For small gaps that don’t close, use putty for that purpose.

Wood putty or wood filler is a mix of sawdust and glue with tint or stain. It comes in a variety of colors, or you can mix your own. You don’t need to worry if it’s not an exact match. There are enough natural color variations in wood that it won’t matter. Find or mix a color that matches the tone of the overall floor.

It’s only a quick, four-step process to fill in narrow floor gaps.

Step 1 – Vacuum out the cracks

Step 2 – Wipe over the top of the crack with a clean towel

Step 3 – Using your finger or a putty knife, gently work the putty into the gap until it’s full. 

Step 4 – Wipe off any excess putty from around the gap.

To see this technique in action, here’s a video to get you started. “Flooring Tips – How Do I Fix Gaps In Oak Flooring?

If you want to make wood filler from scratch, watch this video, “How to Fix Wood Floor Gaps Easily?

Filling Wide Gaps

To fill wide hardwood floor gaps between planks, use strips of wood or shims.  Putty alone will not hold. You can add a touch of glue to keep the new wood in place. Then sand, stain and refinish the floor for a tight, cohesive, fresh look. 

As with any hardwood floor repair, it’s best to do them in the more humid months. 

An alternative to wood shims is to use manila or sisal rope. Use a natural fiber rope, not synthetic. It’s an older technique that works well, depending on the room. You can stain the rope any color, just like wood. Let the stained rope dry before you put it in the gap. Then, use a stiff putty knife to stuff it in the cracks like a boat builder would do. This Old House has a video demonstrating this technique in wide-planks of old pine flooring.

Before you attempt any repair on a hardwood floor, check with the manufacturer, if possible. They may offer a compatible product. 

If the floor has too many gaps or is too old, it’s time to consider pulling it up and installing a new floor. If you decide to pull up the floor, then this article, “How to Choose the Best Wood Flooring Removal Tools,” will save you time.

Is It Time to Concede and Replace the Floor?

If you don’t feel it’s possible to fill in wood floor gaps, sometimes it may be better just to replace the floor and start fresh. For wood with substantial water damage or that sat too long inside a neglected home, this is a more practical and cost-effective solution. Be sure to acclimate the planks before installing them. Always check the humidity level in your home using a digital hygrometer. Then control it using either or both a humidifier and dehumidifier depending on the season. Prevention is much less expensive than continuous repairs. 

If you plan to install a new floor yourself, keep it simple, and visit Easiklip. We have solid, white oak floors that clip together without glue or nails. It is the easiest DIY hardwood flooring available. The results will be a gorgeous, tight-fitting hardwood floor that is warrantied for 25 years and will last for generations.



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  • Bill Grover