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How to Fill Large Gaps in the Subfloor [4 Effective Methods]

Our floor tends to show signs of wear and tear more quickly than any other surface. The subfloor may have gaps or fissures that cause unusual sounds. This problem can be remedied without the help of a professional.

How to fill large gaps in the subfloor?

Large gaps can be filled by rearranging the floors. It’s possible to fill the holes in the subfloor with cement-based fillers or caulk. Wood strips, wood shims, and ropes can be used as flooring gap fillers. The floors can be replaced if these methods don’t work.

This article will explain the various methods for filling subfloor gaps available. So, keep reading!

What Are the Reasons for Large Gaps in Subfloor?

In general, gaps in an old subfloor are relatively common. And they usually have little effect on the stability and reliability of your floor. 

Closing subfloor gaps will not ensure that you will never have mold problems. But it will significantly minimize the likelihood. Additionally, it will prevent vermin infestation.

The reason for wide subfloor gaps must be identified before attempting to fix them. So check the reasons behind it-

If the Subfloor Wasn’t Acclimated

It’s critical to let wood subflooring adapt to your home before installing it. So, before installing a sub-layer, store the boards safely for a few days to acclimatize them.

Too Late to Repair

Timing is everything when it comes to plywood subfloor gaps. Keep an eye on your flooring and notice any changes. The number and size of gaps/cracks impact how the floor felt underfoot and repaired.

Wet Subfloor

Remember to let your subfloor dry before adding your finishing layer. Before putting the cover, you can inspect the dried-out boards for any alterations. Also, you can make any necessary repairs. 

In this case you can use particle board rather than plywood for subflooring. Because a particle board can absorb less water than a plywood board.

Not Checking the Subfloor Before Completion

Inspecting the subfloor before finishing it can help you avoid several issues later. To test the stability and resistance of your soon-to-be floor, walk over the completely dried subfloor.

How Can You Repair Large Gaps in the Subfloor [Easy 4 Methods]

The greatest approach to avoid subfloor gaps is to prevent them in the first place. This may sound apparent. After you cover everything, you can’t examine your subfloor for modifications or minor faults.

However, preventing this type of problem in your home is not always achievable. Fortunately, it’s something that can be remedied with a few helpful hints.

Whether you installed a new subfloor or uncovered the one that came with your house, you may have discovered large gaps in the subfloor. Those gaps could create an issue in the long run. Follow our suggestions to resolve the issue as soon as possible.

Method 1: Rearrange the Floors

Some people urge you to stack the floors as closely as possible when laying the subfloor layer. However, this is not entirely correct.

There should be a 1/8 inch gap at all ends and edges to allow your flooring. That will expand in different weather conditions.

Leaving too much space around the boards may result in a gap between the boards. Those can grow wider and broader with time.

The simplest solution for filling huge gaps in the subfloor is to bring the floorboards closer together. And see how much space is left around the perimeter. If it’s more than 1/8 inch, you’ll need to add some filler to get the correct gap. 

To lay a new subfloor, join the planks and secure them so they don’t move. After the rearranging process you should refinish the hardwood floors of your house.

Method 2: Apply Fillers

To fill gaps in the subfloor, you can use various items. Consider whether replacing the subfloor is desirable if it is damaged or has too many repair points.

We propose using particular items to cover a tiny hole in the subfloor or larger gaps if there are only a few of them.

In terms of subfloor fillers. Typically, you have two choices:

  1. For more extensive areas, a cement-based leveling compound is easier to handle. It has a longer open time which should be used.
  2. Another option is to use caulk. But this material works best with minor gaps or, in general, with subfloors in good shape to begin with. Caulk has the advantage of preventing cracks from growing and is also relatively easy to identify and use.

Method 3: Cut Strips of Wood or Other Materials to Size

Fillers are ideal for filling gaps in plywood or OSB subfloors. But they are not the most aesthetically pleasing way to repair your floor.

Suppose you want something as effective but more natural and long-lasting. As a subfloor gap filler, you can use different materials such as wood strips, wood shims, or ropes.

If you choose to install this way, do so during the hottest part of the day. The gaps will be narrower, and you will avoid harm to your repairs the next time the boards expand.

You can even add glue for added security. As a finishing touch, sand and paint them in the same color as the rest of the subfloor.

Method 4: Install New Floors

Repairing your subfloor is not always possible or prudent. Sometimes the issue isn’t just filling holes; there are minor cracks all over the surface.

Even if they can be filled, you should consider the time and money spent on them. Filling up gaps and cracks won’t help if your subfloor is in bad shape overall. 

In this method you might need to remove glue down from the wood floors sometimes. In that case execute it properly.

It may be a good idea to replace your floors and install a new subfloor. If you intend to sell your home in the future, it may also increase its overall worth.

Here is a product table for using the best woods for installing the subfloors. Check down below-


These woods are reasonable and will go for long lasting. So you can use one of them for your house.

I’ve written up all I know about filling large gaps in subfloors to help you. After reading these instructions, I hope you will have a clear picture of these methods. I can assure you that those are secure and sound.


Question: How much caulk can fill a gap?

Answer: Determine the size of the void to be filled. A single caulk bead can fill up to 1/4 inch of space. If the gap is slightly greater, fill it with caulk but not flush with the surface. Wait until the caulk is dry before applying a surface bead.

Question: How to fill a low subfloor area?

Answer: Fix low spots in wood or concrete subfloor with underlayment, leveler, or patch. Underlayment is a thin layer of material between two others. It insulates, absorbs sound, and protects your floors from damage.

Question: Is spackle and wood filler the same thing?

Answer: Each of these patches serves a specific purpose and has a preferred location. To conclude, caulk should be used for corners and edges, wood filler for flat surfaces, and spackle for drywall.


You now know precisely how to fill large gaps in the subfloor. If you face any problem with these methods, you can call a professional.

When installing subfloors, keep in mind a piece of advice. Subfloors should be checked more frequently to make sure there are no gaps.

Good luck doing your work!