Self-leveling Compound Over OSB

Self-leveling compound over OSB

A self-leveling compound is a cement-based flooring material that can be used to level uneven surfaces, such as concrete or plywood.

It is often used before installing other types of flooring, like tile or hardwood.

When working with OSB (oriented strand board), which is a type of engineered wood commonly used as subflooring, there are specific considerations to keep in mind.

OSB can sometimes swell or warp when exposed to moisture. This can make it challenging to achieve a level surface for flooring installation.

By using a self-leveling compound over OSB, you can create a stable and flat foundation for your flooring. This will ensure that the final result not only looks good but is also structurally sound.

Benefits of using a self-leveling compound over OSB

Some benefits of using a self-leveling compound over OSB include:

  • Improved stability and durability of the flooring system
  • Reduced likelihood of cracking or unevenness in the finished flooring
  • Improved moisture resistance and protection against damage from water or other liquids
  • Improved insulation and soundproofing properties of the flooring system

In the following sections, we will discuss the specific steps and considerations for preparing and installing a self-leveling compound over OSB, as well as maintenance and repair procedures for this type of flooring system.

Preparation of the OSB Substrate

Before applying a self-leveling compound over OSB, it is important to properly prepare the substrate to ensure optimal bonding and adhesion of the compound. Here are the steps to prepare the OSB substrate:

Inspection of the OSB substrate for damage and repair if necessary: 

Thoroughly inspect the OSB substrate for any signs of damage, such as warping, cracking, or delamination. If any damage is found, it should be repaired before proceeding with the self-leveling compound installation. Any protruding nails or screws should also be removed or countersunk.

Cleaning and dusting the OSB substrate: 

The OSB substrate should be thoroughly cleaned and dusted before applying the self-leveling compound. This can be done using a broom or vacuum to remove any debris or loose particles from the surface.

Application of primer to the OSB substrate: 

Applying a primer to the OSB substrate is recommended to improve the bonding and adhesion of the self-leveling compound. Choose a primer that is suitable for use with OSB and self-leveling compound, and follow the manufacturer’s instructions for application.

It is important to note that the OSB substrate should be fully cured and acclimated to the room’s temperature and humidity before proceeding with the self-leveling compound installation. This will help to prevent any moisture-related issues and ensure a stable base for the flooring system.

In the next section, we will discuss the selection of self-leveling compound and the criteria for choosing the best product for use over OSB substrate.

Selection of Self-Leveling Compound

When selecting a self-leveling compound to use over the OSB substrate, it is important to consider several factors to ensure optimal performance and longevity of the flooring system. Here are some of the key factors to consider when selecting a self-leveling compound:

Type of self-leveling compound: 

There are several types of self-leveling compounds available on the market, including cement-based, gypsum-based, and epoxy-based. Cement-based self-leveling compounds are the most commonly used, as they offer good durability, moisture resistance, and leveling properties. However, they can take longer to cure and may require a longer wait time before installing other flooring materials.

The thickness of self-leveling compound: 

The thickness of the self-leveling compound needed will depend on the condition of the OSB substrate and the type of flooring material that will be installed on top. Thicker self-leveling compounds may be needed to level out larger gaps or depressions in the substrate.

Compatibility with OSB: 

It is important to choose a self-leveling compound that is specifically designed for use over an OSB substrate. Some self-leveling compounds may not adhere properly or may cause the OSB to swell or warp.

Moisture resistance: 

Since OSB is prone to moisture-related issues, it is important to choose a self-leveling compound that offers good moisture resistance to prevent damage to the substrate and flooring system.

Environmental factors: 

Consider the temperature and humidity levels in the installation area when choosing a self-leveling compound, as some compounds may have specific temperature or humidity requirements for optimal performance.

Mixing and Application of Self-Leveling Compound

Mixing and applying self-leveling compound over OSB substrate requires careful attention to detail to ensure a smooth and level surface. Here are the steps to mixing and applying a self-leveling compound:

Mixing the self-leveling compound: 

Follow the manufacturer’s instructions for mixing the self-leveling compound. Use a mixing paddle and a drill to mix the compound thoroughly.

Pouring the self-leveling compound: 

Pour the self-leveling compound onto the prepared OSB substrate in a ribbon pattern, working from the farthest corner of the room toward the exit. Use a notched trowel or squeegee to spread the compound evenly over the surface.

Spreading the self-leveling compound: 

Use a spiked roller to spread the self-leveling compound evenly and remove any air pockets. Continue spreading the compound until it is level and smooth. Of the compound and environmental conditions.

It is important to work quickly when mixing and applying the self-leveling compound, as it can begin to set and harden within a short amount of time. Be sure to wear appropriate protective gear, such as gloves and eye protection, when handling self-leveling compounds. 


Once the self-leveling compound has been applied and spread evenly over the OSB substrate, it must be allowed to cure fully before any further work can be done on the surface.

Curing times will vary based on the manufacturer’s instructions and the thickness of the applied compound, but it typically takes several hours to several days. During this time, it is important to keep the area free of foot traffic and avoid any work that could disrupt the curing process.

After the self-leveling compound has fully cured, it can be finished with various flooring options, such as tiles, vinyl, or hardwood. It is important to ensure that the finished flooring is compatible with the self-leveling compound and any adhesives used to secure it to the surface.

If the self-leveling compound is left exposed as the finished surface, it can be finished with various coatings, such as epoxy or polyurethane.

These coatings can provide additional durability and protection for the self-leveling compound surface. Be sure to follow the manufacturer’s instructions for applying and curing any coatings used on the self-leveling compound.

Maintenance and Repair of Self-Leveling Compound over OSB

Proper maintenance and repair of self-leveling compound over OSB substrate is essential to ensure the longevity and performance of the flooring system. Here are some tips for maintaining and repairing self-leveling compounds over OSB:

Regular cleaning: 

Regular cleaning of the self-leveling compound surface is essential to prevent the buildup of dirt, debris, and other contaminants that can damage the surface. Use a mild cleaner and a soft-bristled brush or mop to clean the surface regularly.

Avoiding moisture damage: 

Self-leveling compound over OSB substrate is susceptible to moisture damage, so it is important to avoid exposing the surface to excess moisture or water. Any spills should be promptly cleaned up to prevent damage.

Repairing damage: 

If the self-leveling compound becomes damaged, it is important to repair the damage promptly to prevent further damage to the substrate or flooring system. Follow the manufacturer’s instructions for repairing the self-leveling compound, and be sure to use a product that is compatible with OSB substrate.

Maintaining temperature and humidity levels:

Maintaining a stable temperature and humidity level in the installation area can help to prevent moisture-related issues and ensure optimal performance of the self-leveling compound and flooring system.

Regular inspections and maintenance of the self-leveling compound surface can help to prevent damage and ensure optimal performance and longevity of the flooring system. If you notice any signs of damage or wear on the self-leveling concrete surface, contact a professional installer or contractor for advice on repair or replacement.


Self-leveling compound is a popular solution for creating a smooth and level surface over OSB substrate. By selecting the right type of self-leveling compound and following the proper mixing and application procedures, you can create a durable and long-lasting flooring system.

However, it is important to remember that a self-leveling compound is not a substitute for proper substrate preparation and moisture control. Before installing any flooring system, be sure to assess the condition of the substrate and address any moisture or structural issues. By taking the time to properly prepare the substrate and install the self-leveling compound, you can ensure optimal performance and longevity of the flooring system.

michael Morris