Subfloor
A subfloor is the structural layer beneath finished flooring that provides a stable base across the floor framing system.
What is a Subfloor?
A subfloor is the structural panel or layer installed over floor joists that creates the base for finished flooring materials.
It supports loads, helps stiffen the framing system, and provides the surface onto which underlayment and finish flooring are installed.
Common Subfloor Materials
- Plywood
- OSB (oriented strand board)
- Specialty panels for moisture or tile applications
Why Subfloor Quality Matters
Supports finish flooring: Uneven or damaged subfloors can telegraph through the final floor surface.
Affects stiffness: A solid subfloor helps reduce bounce and movement.
Influences durability: Moisture-damaged panels can lead to squeaks, soft spots, and floor failure.
Common Problems
Squeaks
Usually caused by movement between the subfloor and framing or loose fasteners.
Water Damage
Leaks or humidity can swell, weaken, or delaminate subfloor panels.
Uneven Areas
Variations in height can create problems for tile, vinyl, hardwood, and laminate installation.
Common Mistakes
Installing finish flooring over damaged panels: The surface below must be sound first.
Skipping fastening requirements: Poor fastening can cause movement and noise.
Ignoring flatness: Many flooring products have strict tolerances for the substrate.
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