Choosing the right subfloor for hardwood flooring is crucial for ensuring stability, durability, and an optimal finish. Here’s a breakdown of what to consider when selecting the best subfloor:
1. Type of Hardwood Flooring
- Solid Hardwood: Solid hardwood flooring is more prone to moisture fluctuations, so it requires a sturdy, stable subfloor like plywood or OSB (oriented strand board).
- Engineered Hardwood: Engineered hardwood is less susceptible to moisture, making it more versatile. It can be installed on concrete subfloors with proper moisture barriers or on wood subfloors.
2. Subfloor Material Options
- Plywood: A common choice for subfloors, plywood provides durability and dimensional stability. It is typically available in 3/4″ thickness, which is ideal for supporting hardwood floors.
- Oriented Strand Board (OSB): Another affordable option, OSB offers a solid base but isn’t as water-resistant as plywood. It should be at least 3/4″ thick for stability.
- Concrete: Concrete is generally used for subfloors in basements or ground-level installations. It requires a moisture barrier, such as a polyethylene sheet or a specialized underlayment, before installing hardwood.
- Particleboard: Not recommended for hardwood flooring, as it lacks the stability needed and does not hold nails well.
3. Subfloor Thickness
- Minimum Requirements: For solid hardwood, a minimum thickness of 3/4″ for plywood or OSB is recommended. Thicker subfloors reduce flexing, which can prevent damage to the hardwood above.
- Engineered Wood Flooring: Engineered hardwood can sometimes be installed on thinner subfloors, but thicker subfloors still enhance stability.
4. Subfloor Moisture Control
- Moisture Barrier: For concrete subfloors, use a moisture barrier to protect hardwood from absorbing ground moisture. A polyethylene sheet or a special hardwood flooring underlayment works well.
- Relative Humidity and Moisture Testing: Ensure moisture levels in the subfloor are within 12% of the hardwood flooring. Test the subfloor with a moisture meter to confirm it is dry enough before installation.
5. Installation Method of Hardwood Flooring
- Nail-Down: Requires a wood subfloor (such as plywood or OSB). Solid hardwoods often use this method and need a sturdy base.
- Glue-Down: Works for both engineered wood and some solid woods but requires smooth subfloors, such as plywood, OSB, or concrete. In the case of concrete, a moisture barrier is essential.
- Floating Floor: Floating floors do not attach directly to the subfloor, which makes them suitable for a range of subfloors, including those with minor imperfections. This method is typically used with engineered hardwood.
6. Flatness and Smoothness of Subfloor
- Level Surface: A flat subfloor is critical for preventing squeaks and uneven spots in hardwood flooring. Check for high or low spots and sand or fill them as needed.
- Repair Damages: Address any issues like cracks, holes, or uneven areas. For wood subfloors, loose boards should be nailed down, and concrete cracks should be patched with a leveling compound.
Summary Checklist for Choosing a Subfloor:
- Choose plywood or OSB for wood subfloors, and concrete with a moisture barrier for basement or ground-level installations.
- Ensure adequate thickness (3/4″ or thicker for stability).
- Use a moisture barrier on concrete subfloors.
- Ensure the subfloor is level and smooth to avoid unevenness.
- Match the installation method to the subfloor type for stability and durability.
Selecting the right subfloor based on the type of hardwood, location, and moisture conditions will help ensure a long-lasting and beautiful hardwood floor.