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How Thick Should OSB Subfloor Be? (Read This First!)

Looking for materials for the subfloor but can’t determine which one will work best for you? OSB can be the best choice for the subfloors in many situations. Although, it’s certainly not the best product to use for the subfloor. So, you are thinking, how thick should the OSB be? 

This article will answer the question with many helpful tips and info.

OSB subfloor thickness

For 16-inch standard joist distance, 23/32 inch OSB subfloors will be enough. But if the joist distance is 24 inches, you will need 1-inch OSB boards. You can always go for a thicker OSB subfloor if the floor will be heavily used or you want to install heavy flooring materials such as tiles.

Subfloors are hidden flooring materials under the floor tile or carpet. Subfloors are made of plain boards and glued and screwed with the joists. Subfloors support the floor and weigh anything above the floor. So, as you can see, they have essential components for our flooring.

OSB or Oriented Strand Board is one of the materials used for flooring in modern houses. The use of OSB for subfloor started in the 1970s. It comes in various sizes and thicknesses. So, how thick should OSB be for the subfloors?

The thickness of OSB for the subfloor depends on the distance between the joists. Joists are like small wooden pillars that support the OSB. If the joists are close, the OSB board will need less thickness to support the floor. 

But if the joists are far from each other, you will need thicker OSB.

You can find OSB of many different thicknesses, but not all of them are suitable for flooring. Thinner OSB works well in attic or walls. But flooring needs thicker OSB.

23/32 inch OSB boards are the minimum thickness of the OSB for flooring. You should install 23/32 inch OSB boards, where the joist size is 16 inches. If the joist size is 24 inches, get 1-inch OSB boards.

OSB boards are heavy and dance but less strong than plywood. So you will need thicker OSB boards for the plywood. Usually, plywood is the best choice for most types of flooring, but often situations do not require the best things.

For example, if you have to cover a lot of places, Plywood will be pretty costly, but on the other hand, OSB boards can help you save some money. Plywoods are 20-25% more expensive than the OSB boards.

But what are some of the issues with OSB boards? OSB boards are slightly less strong than plywood, so one should not use them for heavy flooring like tiles or stone on the OSB subfloor. Vinyl, carpet, and other light floorings will be best for the OSB subfloor. 

But heavy flooring is possible if you choose thicker OSB boards.

There are some other issues with OSB boards. It’s less moisture resistant than plywood. The edges of OSB boards can swell in the presence of moisture. OSB boards are made of wooden chips and glues. The wooden chips soak water and swell up. 

The nail holding capacity of OSB is less than wood.

However, although it has some issues, it has some good sides too. OSB boards are cheaper and can save some of your money. As it is made of dense wood, It reduces more sound than plywood. 

I will support OSB boards for their eco-friendly features. The board is made of leftover wood, and you don’t need solid wood parts to make OSB boards. Once installed, OSB boards should last as long as the house’s life. Check out if OSB is suitable for those flooring.

Standard osb subfloor: 

For standard subfloors, OSB is not very suitable. It does not look good on the top of the floor. You need tiles or carpet to cover the OSB Subfloor. 

Basement osb subfloor:

For the basement OSB Subfloor, 23/32 inch OSB boards will be suitable. But if the joist distance is 24 inches, you will need 1-inch OSB boards.

Is 1/2 osb ok for subfloor?

½ inch OSB boards are not suitable for the subfloor. Even ½-inch plywoods are not ideal for subfloors. You will need 23/32 inch OSB boards for the 16-inch standard subfloor.

If the joist size is more than 16 inches, you will need a thicker subfloor. This is a general guideline for subfloors. But you should always check the local building codes of joist thickness and OSB board thickness.

OSB boards are heavy but also quite flexible than plywood. So it will make less sound than the plywood. Moreover, OSB boards will absorb loud sounds.

3 factors that determine osb subfloor thickness

There are not too many thicknesses of OSB boards you can use for your subfloor. Generally, you can use two different thicknesses of subfloor depending on your need. They are 23/32 inch OSB boards and 1-inch OSB boards.

23/32 inch OSB boards are the minimum thickness for the subfloor. If you choose thinner subfloors, your subfloor can become prone to collapse. 1-inch subfloors are needed where the joists are further from each other. 

As OSB is dense and heavy. More than one inch OSB will be harder to work with, although you can choose them for more strength for tiling. Here are the few factors that determine the thickness of your subfloor.

Distance between the joists:

The distance between the joists is the most vital factor determining the subfloor’s thickness. Joists provide support to the subfloor. Generally, there are two different joist spacing. The first is 16 inches, and the other is 24 inches. 

Sixteen inches is the most common joist spacing.

For 16 inches joist spacing, choose 23/32-inch OSB boards; for 24 inches joist spacing, select OSB 1-inch boards.

Flooring materials:

The flooring materials include carpets, vinyl, ceramic, natural stones, etc. For heavier flooring material, OSB boards do not do well. But if you want, choose a thicker OSB board and install heavier flooring. 

Such as, you can choose 1-inch OSB boards for 16 inches joist spacing and install ceramic tile on them.


If you need a heavy-duty floor for a lot of traffic, you can choose thicker OSB boards for your subfloor.

Is it better to use OSB or plywood for subfloor?

So, you are having trouble choosing between the OSB and plywood? In most situations, plywood will do a better job. But if you want to get the jobs done on a low budget, OSB boards will do decently while saving some money.

OSB hardwood floors are less robust than plywood. So, you can not use heavy materials on them. Ceramic tiles and natural stone floors will add more load on OSB boards. 

Plywood is suitable for most types of flooring. Plywood is stronger, and it can take more load than OSB boards. Plywood also has a better nail holding capacity than the OSB boards. 

Working with plywood is easier than with OSB boards, as plywood is lighter. But plywood makes a lot more sound than OSB boards. OSB boards are dense and flexible, so it absorbs more sound.

When it comes to resisting moisture, plywood stands out. Plywood does not change its shape when contacted with moisture. On the other hand, OSB boards can swell up in the presence of water. 

However, once the boards are installed safely, there is less chance of moisture damage.

So, which one should you choose from the plywood and OSB boards? If you prioritize quality and don’t mind spending a bit for a better subfloor, plywood will do the best for you.

But if you are on a budget and looking for boards that will work decently, OSB boards can be a good choice. Certainly, plywood is better than OSB boards in most categories. But OSB is eco-friendly and gives you a decently balanced subfloor.

How to measure OSB subfloor thickness?

To measure OSB subfloor thickness, first, you will have to determine what type of floor you want to install. Do you want to use carpet and vinyl tiles on your subfloor? Follow the tips below to determine the correct thickness for your subfloor.


Measure the joist distance. If it is 16 inches, then go for 23/32 inches. If the spacing is 24 inches, go for a 1 inch OSB board.

Do not install ceramic tile:

Do not install ceramic tile on a 23/32 inch thick subfloor. 24-inch joist size is also not suitable for those types of floors.

Get help from professionals:

Get help from professionals to ensure you are not doing anything wrong.

Final Thoughts

23/32 is the most used OSB for the subfloor as most houses have 16-inch joist sizes. You can also use 1-inch OSB boards if the joist spacing is over 16-inches. Generally, you should not choose thicker OSB boards as it will make the job more challenging as it is very dense and heavy.