Subfloor Requirements for SPC Floor

Stone Plastic Composite Flooring (SPC) is one of the most durable types of flooring. It stands up to dents, dings, and scratches from normal, daily abuse. To keep this type of flooring resilient against wear and tear, you must install it correctly before it’s used.

The first step to proper installation is to get the subfloor in order. SPC is one of the few types of floors that can be safely installed over concrete, wood, or other solid floors.

To help you start your installation project off right, here are a few tips for preparing your subfloor.

Concrete Subfloor

Concrete is one of the most common types of subfloors found in homes. It’s also the subfloor that can hold in the most moisture. No matter the flooring, concrete subfloors should always be cured for at least 60 days before a flooring installation.

To test your subfloor for moisture, you should always take a moisture reading. To comply with the warranties, each manufacturer has a different set of specifications. Most commonly, the maximum moisture condition is 3.0 pounds per 1,000 sq. ft. per 24 hours when tested with the Rubber Manufacturers Association test.

Another way to measure the moisture in a concrete subfloor is to tape a piece of your scrap vinyl to the floor using duct tape. Seal in the edges so no air can escape. After 72 hours, pull the tape off the floor. If it is easy to pull up, your subfloor has too much moisture for vinyl. You will need to dehumidify the room and keep a constant temperature to reduce moisture. Take a moisture rating each week to check the progress.

If you’re ready to move forward, sweep away any dust or debris. You can use a wet vacuum as long as you dry the floor completely before laying any planks.

Next, put a level on your floor. Look around your room for any pockets of high or low spots. Concrete might look smooth, but there are often a few areas that will stand up or sink down.

If you find any low spots, smooth them over using a floor patching compound. Follow the instructions on the compound and then let it dry for at least 20 minutes. Once dry, sand it down with sandpaper and sweep again.

If you have any high spots in your subfloor, sand them down using a belt sander. When you’re done, clean away any debris using a vacuum or broom.

Tile Subfloor

You can install SPC flooring over tile floors, such as ceramic and terrazzo. These floors should be solid and in good condition. The tiles will need to be leveled with cementitious base that will create a smooth and level surface. Follow drying instructions and test for moisture before installing the flooring.

Wood Subfloor

When you install your SPC on a wood subfloor, the top plywood should be a minimum of 1/4″ thick.

For most subfloors, you will need to add an extra layer of wood. To do this, measure and cut the plywood to fit your room. Arrange the plywood on the first layer of wood. Do NOT line up the second layer with joints in the first layer. Make sure you give yourself at least a quarter inch gap along the walls and between each joint so the wood can expand naturally.

When you’re ready, secure the plywood with 1-inch deck screws. The screw-heads should all fall just below the surface of the wood. Cover the gaps between the screw heads and joints with floor patching compound. Allow it at least 20 minutes to dry before sanding it down.

Sweep away any remaining dust or debris. You can also use a wet-dry vacuum for this.

Vinyl Subfloor

In rare cases, a homeowner will install a new vinyl floor over an existing one. If that’s what you’re doing, the first step is to do a deep clean of the old vinyl with floor cleaner. If you don’t have floor cleaner, mix a few drops of dish detergent with water to clean the floor. Allow it to dry completely before moving on.

Look around your room for any cracks or dents. If you see any, use a flooring compound to cover these holes. Allow the compound 20 minutes to dry before sanding away any uneven surfaces.

Dust and sweep up the remaining debris from the floor. Once the floor is clean and dry, you’re ready to install.

Before you move on to the installation, make sure you have all the tools on hand and ready to put to use.


Have questions? Need a little bit of extra help? We’re here for you. Start a chat with one of our flooring experts in the box on this page and get a fast answer to your vinyl flooring installation questions.

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