acceptable gap in hardwood floor
Kristina Davis

Those who know very little about construction have wondered what is the acceptable gap in hardwood floors.

Or why do these gaps in hardwood floors suddenly appear out of thin air?

During one of her house cleanups, Miss Penelope noticed these huge gaps on her floor. She couldn’t remember them ever being present.

Every owner of a home with wooden floors installed would also be asking what the acceptable gap in hardwood floors is.

This article will tell Miss Penelope (hopefully she sees this) and my beautiful readers all there is to know.

There is so much that is to be known about gapping and floors.

The acceptable gaps in hardwood floors are usually very small. They are (less than 2mm in size), sometimes never noticeable. However, this will change over time, especially during colder weather.

What Is Gapping?

what a gapping

For the newbies, gapping is that separation in between the edges of wooden flooring pieces.

During installation, it is common to have those gaps. If they become too wide, they do not help the overall look of the house.

It will make the house look quite unattractive. The gaps also become a hotspot for dirt and debris to converge.

It can also become a tripping hazard as the wood ages and begins to cup.

What Is Acceptable Gap In Hardwood Floor Installation

acceptable gap when installing

The gaps on your hardwood floorboard can appear as a result of errors during installation.

If that is the case, they would appear within a few days. The gaps are usually relatively small, less than 2mm in size.

There you have it if you ever wondered what are acceptable gaps in hardwood floors.

However, take note that wooden boards that are properly installed would hardly develop gaps.

It will happen like so regardless of the weather or levels of humidity. A professional would ensure that the wood boards are properly acclimatized.

He/she would place them in a straight and consistent fashion.

Note: During installation, the floor board may be tightly placed but will separate over time. This process is even faster during winter or colder seasons.

What Is The Acceptable Gap In Hardwood Floor?

what is acceptable gap

Take note that there are no acceptable gaps in hardwood floor, but they appear regardless.

Some of the common causes of gaps in wooden floors include:

  1. Improper spacing during installation
  2. Failure to acclimatize wood floorboards before installation
  3. Improper fitting
  4. Water leaks or excess moisture
  5. Concrete subfloors, as they easily accumulate moisture

Preventing the Gaps Before Installation

preventing gaps

One wouldn’t need medication to save one that is ailed if you can prevent it from the start.

By preventing the gaps, you wouldn’t have to deal with them. You can do so by following the steps itemized below.

Step #1. Understanding The Problem

One can never offer solutions to a problem he or she does not know about nor understand.

The first step to dealing with gaps on floorboards is to understand what they are. And also understand how they come to be.

Step #2. Prepare The Wood

prepare wood

Now that you understand what the problem is, it is time to grab this bull by its horn.

I explained that the cupping of wood is why gaps appear in the first place.

To prevent this from happening it becomes pertinent that the wood intended for installation has to be adequately prepared.

If not prepared it will cave in after absorbing a little moisture.  Or even after weathering a change in climate in just a season.

The wood surface is usually prepared to avoid gapping. The preparation involves enhancing the appearance of wood which will protect it from damage.

Dye, colorant, glazes, sealants, wood fillers, primer, and toner are some of the few things used for this preparation.

Note: The products used in the process of preparation also help to bring out the natural component of the wood.

Step #3. Acclimate The Wood

acclimate wood

Remember I mentioned gaping does not occur in all cases wherein wood has been installed.

Gapping will not occur if the installation had been handled by a professional who understands his or her craft.

In addition to expertise, the trick is that before installation, they ensure that the wood undergoes acclimation.

Acclimation entails ensuring that the temperature and humidity of the wood meant for installation matches that of the room it is to be installed in.

If the wood has higher moisture content than the room, it will contract after installation.

It can eventually shrink (then in comes the gaps). Whereas, if the moisture content is lower, it expands and cups.

Steps to acclimation

  • Endeavor to store wood in the room where it is to be installed. The acclimation process can take between seven to ten days.
  • Your HVAC should be set to the same temperature as your normal routine.
  • To increase airflow, stack the wood in a log cabin formation
Note: The more the airflow between the wood, the faster the acclimation process.

Step #4. Regulate Humidity Levels In The House

regulate humidity

The major cause of gapping is the contraction and expansion of the wood. This in turn is caused by the presence of humidity in the home.

Maintain the level of humidity in the home to a certain level. If you can do this consistently then you’d have achieved a lot.

This is because it will greatly reduce the chances of expansion and contraction after installation. Thus, it won’t be birthed.

How to regulate humidity

  • Reduce ventilation
  • Add moisture; a humidifier can come in handy here.
Tip: It is recommended that you keep the home’s humid level at 35 and 55%.

Dealing with Gaps in Hardwood Floors after Installation

dealing with gaps

Okay, Miss Penelope (and yourself) knows how those gaps on your wooden floorboards came about. And also knows how to prevent them before installation.

Now the question is, “Is there salvation after installation?” I’ve got a few tricks up my sleeves I can show. They will deal effectively with the problem;

  • Wood putty
  • Wood strips
  • Rope

Wood Putty

Local stores usually have wood putty, ensuring you pick a color that matches your floor board except if you want to go crazy with colors.

The application is very simple;

This is the simplest way to deal with those gaps and should be an easy fix as long as the gap doesn’t widen.

  • Ensure that the floor is clean
  • In a circular motion, apply the putty to the affected areas
  • Clear excess putty with a blunt knife and wipe away any other debris with a damp cloth
  • Now leave to dry

Wood strips

the wood strips

This is also a quick fix. If there are leftover wooden floorboards, they’ll be of great help here; if not, salvage for wooden floorboards whose color match yours.

Here’s what to do:

  • Measure the length and breadth of the gaps
  • Go on to cut strips of wood from the pile you gathered, just ensure that it is in line with your measurement.
  • Use wood glue to hold them in place.  A hammer or mallet can also be used to drive it in firmly (hit mildly)
  • Sand and stain the spot so it becomes level with the rest of the floor.


the rope

Using natural rope-like cotton is also a good method to fill gaps. Here are easy steps:

  • Always clean the area in and around the gap
  • Use a rope slightly bigger in diameter. Dip this in a bucket of color that matches the color of your floorboard
  • Carefully stretch the rope and leave it to dry then place it in the gap
  • Use a blunt knife to push the rope in so it stays fitted
  • Wood glue can be applied for firmness
  • Clean the area afterward
Note: not all gaps would require fixing. If what your hardwood floor is experiencing is just seasonal gaps then it will close up on its own.


I guess miss Penelope and yourself are grateful for this piece, not only have you gained valuable knowledge about the acceptable gap in hardwood floor.

You also know how to prevent it, and also how to do away with it if you have already experienced it.

Be sure to remember that some gaps may just be seasonal problems. Whenever in doubt, always call the attention of professionals.