Floor Preparation Standards
Floor Prep: The Foundation of a Quality Flooring Installation
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.
For flooring installation, “flat” and “level” are not the same thing. Construction tolerances for a home’s general levelness can be quite forgiving, but flooring installation requires much tighter tolerances to protect the integrity of the product. For example, glue-down installations typically require the subfloor to be within 3/16 inch over a 10-foot span, while floating floors—those that click together without adhesive—require 1/8 inch over 10 feet. That might not sound like much, but even small dips or humps can cause soft spots, hollow sounds, or boards that separate 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.
The process starts by completely clearing and cleaning the subfloor—whether concrete or plywood—then checking it with a long aluminum straightedge. The installer slides the straightedge over the surface to identify high and low spots. Low areas are marked with an “X” to be filled with leveling compound, and high spots are marked with an “O” to be ground down. Often, both grinding and leveling are required to achieve a truly flat surface. Even after leveling, final sanding or grinding may be necessary to smooth transitions between poured and unpoured areas.
Before applying any leveling compound, a floor bonding primer is used. This critical step allows the compound to adhere properly and seals the pores of the subfloor to prevent over-absorption. Without primer, the leveling material can dry unevenly or fail to bond, compromising the entire install. The primer also minimizes stress on the subfloor by preventing excess moisture from soaking in.
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.