You probably know what kind of floors you have in your home – tile, hardwood, linoleum, for example. But do you know what material your subfloor is made of?
Subflooring is the part of a building’s structure that the floor is laid on top of. It is sandwiched between the floor itself and the joists of the building. There are many common subfloor materials, including concrete and plywood.
Floors are obviously important because they give us something to stand on. Naturally, it follows that floors need something to lean on too. This is where subfloors come into play. They provide stability and a sturdy base for the floor.
The quality and material of your subfloor can be critical in determining what type of floor to install and how. Whether you nail, glue, or float your floors doesn’t just boil down to personal choice. Certain subfloors are more or less compatible with different installation techniques. How much weight your floor can carry depends on how well your floor structure has been designed.
Subfloors that are installed improperly – or using the wrong materials – can cause structural failures, excessive movement, sagging, and squeaking. It is important to be knowledgeable about subfloors before making any big decisions about a new floor.
Keep reading to learn about the four most common types of subfloors. In addition, we’ll explore the characteristics that determine their quality and long-term performance implications.
4 Common Subfloor Materials
There are four primary materials used as subfloor:
- plywood & existing hardwoods
- oriented strand board (OSB)
- high-performance panels
Although there are other subfloor and underlayment materials out there, they are generally used in more niche situations.
The construction industry is constantly evolving. For example, magnesium oxide (MgO) boards have become a common subfloor type in recent years. They are considered an eco-friendly alternative to concrete, drywall, and other building materials.
What Makes MgO so Eco-Friendly? This type of subfloor doesn’t contain any asbestos, silica, ammonia, formaldehyde, or benzene chemicals. Yay for no toxins! Also, MgO boards are very lightweight and durable.
This helpful guide lists the most common subfloor types. We’ll break them down one by one so you can make informed decisions about your flooring projects.
#1: Plywood & Existing Hardwoods
Plywood is probably the most common subfloor material out there. In fact, until the 1980s, it was just about the only subfloor used in single-family homes.
How is it made? Fabricated sheets of wood veneer are layered and bonded together with special adhesives under heat and pressure.
Because these layers are cross-laminated and layered, plywood subfloor isn’t susceptible to expansion and contraction (like hardwood). Plywood typically comes in interlocking sheets that measure 4 feet by 8 feet and are either 5/8 or ¾ inches thick.
Plywood sheets have a tongue and groove that interlock. Because of this, this material makes an incredibly secure base for just about any flooring, including hardwood, laminates, and bamboo.
If you decide to use plywood, make sure to apply subfloor adhesive to the top of the floor joists. This will prevent the subfloor from moving around and squeaking.
Another option is to use your existing wood floor as a subfloor. Yes, this is sometimes possible! There are some conditions, however:
- make sure that doing so won’t cause height differences between rooms
- ensure the current floor is clean, dry, level, and structurally sound
As long as your hardwood is at least 5/8″ thick, you should be able to nail down to it. You might also be able to glue onto it with a little sanding first (this will depend on the finish).
In either instance, it’s advisable to seek the help of a flooring professional.
#2: Oriented Strand Board (OSB)
The name might initially seem strange, but it all makes sense after you understand how oriented strand board is made. Essentially, OSB is comprised of multiple 3- to 4-inch wood strands that have been layered in a criss-cross pattern.
These strands are then glued and pressed, creating a board that is denser and absorbs less water than plywood. The result is a durable surface with virtually zero defects. Like plywood, installing OSB requires the boards to be glued or nailed to the floor joists.
Generally speaking, ¾-inch thick bamboo (solid) floors are installed right over a ¾-inch thick OSB subfloor. The planks are placed at a 90-degree angle across the floor joists. This pattern stabilizes and strengthens the whole flooring system.
When installing engineered, solid, or floating floors less than ½-inch thick, consider adding a 3/8-inch or ½-inch thick plywood underlayment. When glued or screwed onto your OSB subfloor, this will add stability.
When comparing plywood vs. OSB, many prefer OSB’s smoother surface and long-term sustainability. Plus, the lower manufacturing cost of oriented strand board can help keep home renovation budgets lower.
Did You Know? Installing OSB is similar to installing a plywood subfloor. This means that you won’t need special tools to install it.
#3: Concrete Slab
You may think choosing concrete as a subfloor material will solve all your moisture problems, but concrete is susceptible as well. Concrete slabs are created using water, and they can take months to dry out fully.
These concrete slabs are typically 4 to 6 inches thick and 3,500 – 5,500 pounds per square inch (psi).