How to Fix Uneven Plywood Subfloor

Are you dealing with an uneven plywood subfloor in your home? It can be challenging to level out, but don’t worry – it’s not impossible! Here, we’ll provide you with step-by-step instructions on how to fix an uneven plywood subfloor.

If you are a homeowner engaged in home improvement projects, you may already know the importance of an even subfloor. Properly laying plywood can help ensure floors are level and stable for years. Unfortunately, wooden subfloors often become uneven over time due to settling or shrinkage; however, fixing these issues with some elbow grease and a few simple tools is possible. In this guide, we’ll show you how to fix uneven plywood subfloor in just five easy steps!

How to Fix Uneven Plywood Subfloor

What are the Causes of Uneven Plywood Subfloor?

1. Poor Installation Technique: If the subfloor is not installed properly, it can cause unevenness in the floor.

2. Moisture Damage: Moisture can cause wood to warp and swell, leading to an uneven surface.

3. Structural Issues: Houses often settle over time, causing portions of it to sink or move slightly, resulting in an uneven subfloor.

4. Warping of Plywood Sheets: Improperly stored plywood sheets may succumb to warping due to extreme temperatures or humidity levels, leading to an uneven floor surface when they are laid down on the subfloor.

5. Sagging Joists: If the joists that support your subfloor start to sag, it can also cause an uneven surface.

By understanding the causes of an uneven plywood subfloor, you can better prepare for fixes and repairs before they become a major issue!

Causes of an Uneven Plywood Subfloor

What Will You Need?

Before you can tackle the project, make sure that you have all of the right materials and tools. Here is a list of what you will need:

  1. Screwdriver
  2. Pry Bar
  3. Hammer
  4. Nails
  5. Wood shims or wedges
  6. Leveler
  7. Plywood

Once you have all of your materials gathered, you can move on to the next step.

10 Easy Steps on How to Fix Uneven Plywood Subfloor

Step 1: Inspect Your Subfloor

The first step in the process is to examine your subfloor and figure out where the problem areas are. Check the boards for any soft spots or weak points, as these will need extra attention. You should also look for splits and gaps that have developed over time. Mark these places so you know exactly where to focus your efforts.

Check the Boards 
For Any Soft Spots

Step 2: Remove Excess Nail Heads

Before you can start leveling out the subfloor, you’ll need to remove any excess nail heads sticking up from the floorboards. Use a screwdriver or pry bar to do this carefully – don’t damage the wood! As you work, double-check to ensure all the nail heads have been successfully removed.

Step 3: Place Wood Shims or Wedges

Once all of the nails have been removed, you can begin to place wood shims or wedges in between the floorboards. This will help raise any low spots and level out the surface. Make sure to use a leveler to ensure that the areas are even.

Step 4: Hammer in Nails

Using a hammer, drive nails into each wood shim or wedge so they stay firmly in place. If you need to, you can add additional boards for support. You can also use nails for the edges of the floor to help secure them into place.

Step 5: Apply Plywood Overlay

The final step is to apply an overlay of plywood over your subfloor. This will provide extra stability and strength while also helping smooth out any remaining uneven areas. Cut the plywood to size and secure it with nails.

Step 6: Test and Recheck

When you’re finished, it’s important to test your work. Walk around the area to check for any remaining uneven spots. If you find any, repeat the steps above until everything is level.

It’s Important to 
Test Your Work

Step 7: Clean Up

When you’re finished, it’s time to clean up. Sweep or vacuum the area to remove any dust and debris that may have been created during the process. You can use a damp cloth to clean up any excess glue or adhesive.

Step 8: Prime and Paint

If desired, you can now prime and paint the subfloor. This will help protect it from wear and tear in the future. Be careful not to get any paint on the wood shims or wedges, as this could cause them to become soft and break down over time.

Step 9: Reinforce With Screws

Finally, you should consider screwing down your plywood overlay for extra reinforcement. This will ensure that it stays secure over time. Additionally, it will prevent any warping or buckling of the material.

Step 10: Enjoy Your New Subfloor!

The last step is to enjoy your new subfloor! With some patience and dedication, you can easily level out your plywood subfloor and ensure it is strong and stable for years to come. Remember to regularly check for any signs of wear and tear, which will help you keep your subfloor in top shape.

By following these steps, you can be sure that your plywood subfloor is even and stable. We hope this guide has helped show you how to fix uneven plywood subfloor!

5 Additional Tips and Tricks

1. Use a straightedge to identify high spots and valleys on the floor.

2. Make sure to fill in any large gaps or holes.

3. Sand down any high spots until the floor is even.

4. Apply a self-leveling compound to further level the subfloor before adding new flooring material.

5. When installing your new floor, use a spacer or shims between boards to ensure that they are evenly spaced and will not create an uneven surface when finished.

Following these steps will help you fix an uneven plywood subfloor quickly and efficiently so your new floor looks great and lasts for years!

5 Things You Should Avoid

1. Do not put too much pressure on the subfloor when sanding or filling in gaps. This can cause further damage to the floor.

2. Avoid using an extremely powerful sander, as this could accidentally make the issue worse instead of better.

3. Don’t use plywood sheets that are not thick enough for your project.

4. Don’t install hardwood floors directly onto uneven plywood without first leveling it out, as this will cause your new floor to look misshapen and uneven over time.

5. Lastly, don’t forget to wear a dust mask when sanding down any high spots, as wood dust can be hazardous if inhaled!

With these tips and tricks, you’ll be able to fix an uneven plywood subfloor in no time easily! Good luck with your project!

Avoid Using an Extremely 
Powerful Sander

Will Plywood Flatten Over Time?

Yes, plywood can flatten over time if it is exposed to humidity and temperature changes. Plywood is made up of many layers of wood veneer that are glued together into a single sheet. Over time, the wood will naturally start to expand or contract with environmental changes, which can lead to warping or unevenness in the subfloor. To prevent this from happening, it is important to make sure that your plywood subfloor is properly sealed and regularly maintained. 

Additionally, if you are installing new plywood over an existing subfloor, make sure that the boards used fit together snugly without gaps to limit the warping or shifting of the floor.

With these tips in mind, you can keep your plywood subfloor flat and even for many years to come.

Does Water Weaken Plywood?

Yes, water can weaken plywood if it is allowed to seep into the material. Plywood is made up of many layers of wood veneer that are glued together with waterproof adhesive. If water does get in between these layers, it can cause the glue to become weak and lead to separation or warping over time. 

Additionally, when plywood gets wet, it will start to swell and expand, which can also lead to an uneven subfloor surface. This is why it’s important to make sure that your flooring material is properly sealed on all sides before installation.

By following these tips, you should be able to keep your plywood subfloor strong and stable for many years!

Which is Stronger, Wood or Plywood?

When it comes to strength, wood is generally stronger than plywood. This is because wood has a consistent grain pattern that provides structural support throughout the entire piece of material. Plywood, on the other hand, is made up of many layers of wood veneer that are glued together with adhesive. While this makes plywood more flexible and resistant to splitting or cracking, it also means that it’s not as strong as solid wood.

That being said, plywood can still be used in many applications where strength is needed if you choose the right type and thickness for your project. Additionally, using good quality waterproof glue when installing plywood can help ensure that your subfloor will remain strong and stable for years.

By knowing the difference between wood and plywood, you can make sure that your subfloor is strong enough to support whatever flooring material you choose!


How to fix uneven plywood subfloor is a fairly straightforward process once you know what to do. You must measure your space, purchase plywood that fits the area, and install it properly. With this in mind, your room will soon look even better!

Even though finishing an uneven plywood subfloor can be difficult at first, there’s no reason to be intimidated. All the materials you need are available at most hardware stores, and with some nice measuring tools, you’ll get the job done in no time.

Don’t be afraid to take on the challenge – nothing says pride like completing a successful DIY project!

Photo of author

Adrian Green

Adrian has been interested in woodworking since he was a child. His father had a woodworking shop, and Adrian would help him out and learn from him. He gained basic carpentry knowledge as well as an understanding of how to work hard and take care of business. He enjoys woodworking as a hobby. He loves the feeling of creating something with his own hands, and the satisfaction that comes from seeing his finished products used by others. So he started this blog to spread his passion and knowledge to those interested in DIY wood-working projects. He knows that with a little guidance and practice, anyone can create beautiful pieces of furniture or décor from scratch.

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