When most people plan their flooring project, they think about the color, style, or pattern—but not the floor underneath. Yet, proper floor preparation is what determines whether a floor will perform beautifully for decades or start showing issues within months. The reality is that very few floors are perfectly flat, even in new construction. Homes shift, settle, and breathe with the seasons, and without proper preparation, that movement will show up in the flooring.
The Value of Proper Preparation
For flooring installation, “flat” and “level” aren’t the same. A home’s general levelness can be forgiving, but flooring requires much stricter tolerances—typically 3/16" over 10 feet for glue-down and 1/8" over 10 feet for floating floors. Even small dips or humps can lead to soft spots, hollow sounds, or boards that shift and “pop” over time.
This is why professional installers take ownership of the subfloor just as a finish carpenter would with back-framing before installing custom millwork or paneling. It’s not about perfection—it’s about consistency. The goal is to ensure the flooring can lock together properly and stay that way as the building naturally expands and contracts
Subfloor Preparation Steps
Proper subfloor preparation is one of the most important—and labor-intensive—parts of any flooring installation. It requires time, precision, and the right tools to ensure a stable, long-lasting result.
01. Clear and Clean
Remove all debris, dust, and residues from the concrete or plywood surface to ensure accurate inspection and proper adhesion later.
03. Mark Highs and Lows
Mark low spots with an “X” (to be filled with leveling compound) and high spots with an “O” (to be ground down).
05. Final Smoothing
After leveling, sand or grind again to smooth transitions between poured and unpoured areas.
By investing in proper preparation from the start, you ensure a smoother installation process and a floor that performs exactly as it should for years to come.
02. Check for Flatness
Use a long aluminum straightedge to slide across the surface, identifying high and low areas.
04. Grind and Level
Grind down raised areas and fill low spots with a floor-leveling compound as needed—often both steps are required for a truly flat surface.
06. Prime the Subfloor
Apply a floor bonding primer before leveling to promote adhesion and seal the surface. The primer also prevents uneven drying, poor bonding, and excess moisture absorption.
Why Proper Prep Is Worth the Investment
It’s important for homeowners to budget realistically for this preparation work. Leveling costs vary widely depending on the floor’s condition—typically $1 to $4 per square foot—but it’s the single most important investment in your floor’s longevity. If necessary, it’s better to choose a mid-grade flooring product and allocate more toward prep than to spend everything on premium material installed over an uneven surface.
At the end of the day, proper prep means fewer issues, longer warranties, and a floor that feels as solid and seamless as it looks. Skipping it to save money is like building a house on sand—you might not see the problem right away, but it’s only a matter of time.
