Is it necessary to have a subfloor?

Author: Rudy Baumbach  |  Last update: Tuesday, November 11, 2025

The importance of a proper subfloor system. A subfloor serves as the critical foundation between your home's structural frame and the finished flooring material. It provides essential support, stability, and a level surface for your hardwood installation.

Is a subfloor necessary?

Above grade, hardwood, carpet, laminate and other floor coverings need a plywood or OSB panel subfloor, as they cannot be installed directly to floor joists. Below grade, a plywood or OSB subfloor is optional, depending on your choice of flooring.

What flooring doesn t need a subfloor?

Ceramic & Porcelain Tile

A major benefit of ceramic or porcelain tile floors in the basement is that you don't need an underlayment or subfloor beneath them. You can lay the tile directly over the concrete, as long as the slab is clean and level.

Does every house have a subfloor?

Except for those that have concrete slabs, all houses have joists. While there are some instances where you could have less layers to your flooring, that would be the exception to the rule. In almost every instance there is the floor covering, the underlayment, the subfloor, and the floor joists.

Do all floors have subfloors?

Floor covering is the topmost layer that you see and walk on such as ceramic tile, solid wood, laminate, engineered wood, luxury vinyl, or carpeting. Floor covering is not structural, so it will always have a subfloor under it.

Do I Need An Underlayment For My LVP Flooring?

Do I need a subfloor over concrete?

While a subfloor is not necessary to add structural strength when you'll be laying finish flooring on top of a concrete slab (as in a basement remodel), subflooring over concrete offers two other advantages: Dampness control. Install a vapor barrier of plastic sheeting before laying the subfloor.

Should I remove subfloor?

When Should You Replace Subfloors? There are many signs that your damaged subfloor should be replaced with a new subfloor. These include squeaks and other noises, cupping or warping, cracked or popped tiles, sagging or unevenness, the smell of mold or mildew, or bubbling tile.

How many years does subfloor last?

There are many factors that can affect its longevity, such as the material, the amount of moisture it's exposed to, etc. However, most subfloors can last as long as the home itself. That said, you may have to replace your subflooring after 20 to 30 years if it has absorbed too much water too often.

Can I use an existing wood floor as a subfloor?

As NWFA Guidelines indicate, the only wood flooring you can install directly to a solid board subfloor or an existing wood floor is ¾” solid or engineered wood flooring. These types of floors can be installed perpendicular to or on a diagonal to the direction of the existing flooring.

Does subfloor need ventilation?

Ground moisture rising into or entering the subfloor space can create a damp environment which encourages timber rot, fungus growth and the potential for termite activity. Subfloor ventilation increases air flow, reducing any damaging water vapour in the subfloor space.

Is subfloor just plywood?

Both plywood and OSB are effective choices for your subfloor needs, but OSB may be a better option for a garage than plywood. Plywood is a better option for projects that require a lot of cutting and molding, while OSB is a good option for those who need to cover areas where moisture exposure may be an issue.

Can I put flooring directly on subfloor?

Most modern vinyl flooring, such as Happy Feet, comes with an attached underlayment or pad, often with a moisture barrier built-in – unless the pad is cork. If the product you choose doesn't have an attached underlayment, you can almost always install directly over the subfloor without one.

What happens if subfloor is not level?

Use an underlayment, floor leveler or floor patch product to fix low spots in a wood or concrete subfloor. An underlayment is a thin layer of material sandwiched between two other materials. It's used to help insulate, absorb sound and reduce wear on your floor. It can also serve as a vapor barrier.

What do contractors use for subfloor?

Plywood is considered the most popular material used for subflooring, it has been used since the 1950s and remains one of the top choices for contractors. Standard plywood works perfectly fine as a subflooring material, but the best option is ¾” tongue-and-groove plywood subflooring.

Do wood floors need a subfloor?

Without a proper subfloor, even the highest quality hardwood flooring can develop problems like squeaking, sagging, or warping over time. Think of it as the backbone of your flooring system – while it may not be visible, its role is absolutely vital for long-term performance.

Is it okay to lay new flooring over old flooring?

While you can successfully install certain types of flooring over old surfaces, doing so often comes with risks like uneven surfaces, potential moisture issues, and door clearance problems.

Do flooring companies replace subfloor?

Installing subfloors incorrectly could lead to costly repairs and additional replacements down the road. It's best to work with a local flooring contractor to replace subfloors, but you can DIY the project if you have experience installing them, which could save you between $25 and $30 per hour on labor costs.

Is a subfloor good or bad?

Key Thought: Subfloors, often made from plywood or OSB, are the unseen heroes beneath our feet. They give a sturdy platform for your chosen flooring material and distribute weight evenly to prevent warping and creaks. But beware - improper installation over floor joists can lead to big problems like water damage.

What comes after subfloor?

Underlayment. Underlayment is a layer of material between the subfloor and the finished flooring. Underlayment provides a smooth, level surface for installing luxury vinyl tile, laminate flooring, and hardwood floors. There are different types of underlayment, each with their own purpose.

Is subfloor ruined if it gets wet?

A wet subfloor doesn't always need to be replaced, but it must be thoroughly dried and assessed for damage. Use fans and dehumidifiers to dry it out. If the subfloor is swollen, warped, or has mold growth, replacement is necessary.

How to tell if a subfloor is bad?

Sagging or Uneven Floors: A Clear Indicator of Structural Issues
  1. Water damage: Moisture is one of the most common causes of subfloor issues. ...
  2. Inadequate support: If the floor joists are too far apart or not properly supported, the subfloor can start to bow under the weight of the floor covering and furniture.

Is it OK to have gaps in subfloor?

Improperly spaced and placed subfloor panels can cause performance issues and lead to various structural failures, such as raised joints or buckling. While installing panels too tightly or without any gaps won't allow the material to expand and contract, leaving too much gap can cause excessive movement and noises.

What is the purpose of a subfloor?

Its primary function is to provide a stable, flat surface for the installation of the finished floor. Subflooring acts as a structural support system for your flooring, distributing the weight of furniture, foot traffic, and other loads evenly.

What is the cheapest subfloor option?

Particle board is a material made from wood chips and shavings that are bonded together with glue. It is the cheapest type of subflooring but is also not as durable. Wood board is among traditional flooring materials but has been mostly replaced by plywood subflooring.

Can I pour concrete over plywood subfloor?

The answer is yes! You can install concrete over plywood.

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