5 Easy Steps: How to Waterproof Osb Subfloor

Waterproofing your OSB subfloor is important to make it last longer. This can be done if you build a new house or repair existing floors. 

How to Waterproof Osb Subfloor

It helps protect the floor from moisture and other damage. It would help if you cleaned, sanded, primed, and put on sealer to waterproof the floor. 

It’s easy, and you can do it by yourself. You can find step-by-step instructions on how to waterproof OSB subfloor below.

Steps on How to Waterproof Osb Subfloor

Step 1: Inspect the OSB subfloor

First, look at the OSB subfloor very carefully. Make sure it is in good condition and does not have any problems. If there are any issues, fix them before going on. 

Next, clean the surface of the OSB subfloor by vacuuming or sweeping away any dirt and dust. This will help ensure that the waterproofing adheres properly.

Step 2: Use a Primer

Before waterproofing your OSB subfloor, use a primer to make it stick better. Give the primer time to dry before doing anything else. 

If there are any holes or cracks in the floor, fill them with heavy-duty construction adhesive. Make sure to use enough adhesive to seal the area and waterproof.

Step 3: Apply Waterproofing

Once the primer has dried, apply your chosen waterproofing material. Use a paint roller to evenly spread the waterproofing over the entire surface of the OSB subfloor. 

Apply Waterproofing

Cover any cracks or areas that may be prone to water damage. Allow the waterproofing material to dry completely before continuing. 

This could take several hours, if not days, depending on the product you’ve chosen and the temperature in your home.

Step 4: Apply the Second Coat

Once the first coat of waterproofing has dried, apply a second coat for extra protection. This will help keep your OSB subfloor safe and dry. 

Again, allow the second coat of waterproofing to dry completely before continuing. 

Depending on the product you’ve chosen and the temperature in your home, this could take several hours or days.

Step 5: Cleaning part

Once the OSB subfloor has been completely waterproofed, you’ll want to clean it up and remove any excess material. 

Cleaning Part

Carefully use a vacuum or broom to remove all dirt and dust from the surface of the OSB subfloor. This will help ensure that your floor is debris-free before installation.

These steps help make sure your OSB subfloor does not get wet. If you follow the directions, it will stay dry and safe for a long time. 

Try to keep this part of your home from getting damaged.

Tips for Waterproofing Osb Subfloor

  1. When you install the OSB subflooring, wear gloves, goggles, and a mask to keep yourself safe. This will protect you from dust particles.
  2. Make sure that your floor is completely dry before you start waterproofing it. To check for moisture levels, use a moisture meter or hygrometer to determine how wet/dry your OSB subfloor is.
  3. Before you start to waterproof the osb, clean it with a vacuum cleaner. Remove any dirt, dust, or debris that is on the surface.
  4. Before waterproofing your OSB subfloor, layer asphalt-felt paper over it. This will help protect it from water damage.
  5. Cover all edges and seams with self-adhesive waterproof membrane tape to help prevent water infiltration.
  6. Cover the subfloor with a special paint or sealant to protect it from water damage. Make sure to cover every inch of the surface.
  7. Allow the paint/sealant to dry completely before walking on the OSB subfloor. When you are painting or sealing something, remember that different products require different amounts of time to dry. 

These are easy steps to help waterproof your OSB subfloor and keep it safe from water damage. This will allow you to enjoy a worry-free environment with an OSB subfloor that is both safe and durable.

Advantages & Disadvantages of Waterproofing Osb Subfloor:

Advantages & Disadvantages of Waterproofing Osb Subfloor


  • A seal can help keep water out of your house. This extra protection helps stop water damage.
  • Putting a sealant on your floor can help it last longer. It will also protect the floor from warping or swelling if it gets wet.
  • Waterproofing your Osb subfloor also helps protect it from mold and mildew growth.
  • It can help improve the overall aesthetics of your space, creating a better-looking floor.


  • To waterproof your OSB subfloor, you need to do some extra work. Sand and clean the surface before you apply the waterproofing.
  • Waterproofing a subfloor made of Osb might cost more than other types of flooring.
  • Waterproofing is not a forever fix. You need to do it again sometimes, depending on what kind of waterproofing product you use and how good it is.
  • You may need extra tools like a roller or sprayer to put the waterproofing on correctly.
  • Fixing or replacing a waterproof Osb subfloor can be hard. You have to remove the waterproof coating before doing any repairs.

How Often Should You Reapply the Waterproof Coating?

Every three years, you should put a waterproof coating on your floor. This will stop water from entering the subfloor and keep your house dry. 

Before you cover it with the coating, clean off any dirt or mess with a high-pressure washer and let it dry completely. 

How Often Should You Reapply the Waterproof Coating

Make sure your subfloor is clean and dry before you put a waterproof coating on it. 

Follow the instructions from the manufacturer to apply it correctly. Taking care of your subfloor will help it stay in good shape for a long time.

How Do You Maintain a Waterproofed Osb Subfloor?

Once you’ve waterproofed your OSB subfloor, it’s important to maintain it properly. 

Here are some tips on how to keep your OSB subfloor waterproof:

  • Inspect the floor regularly for signs of water damage. If any is found, repair the affected area as soon as possible.
  • Consider applying a topical sealant to your OSB subfloor. This will help keep moisture out and prevent the occurrence of water damage.
  • When cleaning your subfloor, don’t use any cleaners that contain harsh chemicals. These chemicals can damage the waterproof layer of your subfloor.
  • Clean up any wet messes right away. If water stays on the floor too long, it could damage the subfloor and make waterproofing not work.

Do the steps below to help keep your OSB subfloor waterproofed and in good condition. If you do them, it will last for a long time.

Frequently Asked Questions

What is the Best Epoxy Sealer for Osb Subfloor?

When deciding on the best epoxy sealer for an Osb subfloor, remember a few things. It is important to use a sealer made for OSB when sealing OSB. 

Think about how much traffic the area will have – some sealers are stronger than others. Also, think about how much time and effort you want to put into the job – some epoxy sealers take more work than others.

How Long Does It Take for the Waterproofer to Dry?

When you use a waterproofer on an OSB subfloor, it takes different amounts of time to dry. 

It depends on what kind of waterproofer you are using, the temperature and humidity in the room, and how much product was used. 

Usually, water-based sealants take up to 24 hours to dry, and solvent-based sealants can take 12 to 24 hours. Check the instructions on the package for more exact drying times. 

Do not walk on the subfloor until it is completely dry. This can help prevent any future damage or issue with your OSB subfloors.

How Often Should You Reapply the Waterproof Coating on an Osb Subfloor?

Putting on a waterproof coating every three years is a good idea. This will help keep water away from the floor, protecting your house’s parts underneath. 

Before putting on the coating, clean it with a high-pressure washer and wait until it is completely dry. Before you start, make sure the surface is clean and dry. 

Use a waterproof coating to protect your Osb subfloor. Read the instructions carefully before applying it. Regular maintenance will help your Osb subfloor stay in good shape for many years.


Waterproofing your OSB subfloor is essential for ensuring a long-lasting and durable floor. 

Before waterproofing, you must clean the surface and remove dirt and bits. You can use special sealers or membranes to keep water from the floor. 

I hope this article has helped you learn how to waterproof OSB subfloor. If you liked this article, be sure to check out the other blog post.

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