Most flooring problems that show up months later are installation-condition problems, not product defects. If a subfloor is wavy, floating LVP flexes and stresses the joints. Hardwood can rock, squeak, or show uneven edges. That’s why you should treat flatness like a specification that belongs in your scope of work, not a casual promise.
The Flatness Numbers to Know
Flatness is measured as the maximum deviation over a given length. Common planning tolerances include 3/16" over 10 feet for many floating LVP products, with some manufacturers also requiring 1/8" over 6 feet. Glue-down LVP often demands a flatter substrate because adhesive needs consistent contact, and many installers aim for about 1/8" over 10 feet depending on product and adhesive system. Hardwood tolerances vary by construction and plank width, but 3/16" over 10 feet is a common target, and wider planks may require stricter flatness to prevent rocking and squeaks.
How Flatness Is Measured
A professional flatness check uses a 6-foot or 10-foot straightedge or a laser system across multiple directions, not just one pass down the room. High spots and dips are identified and marked, then addressed before the first plank goes down. A reputable installer can tell you the tolerance they are installing to, what tool they use, and how they verify the subfloor meets spec.
What Happens If Flatness Is Ignored
With click-lock LVP, an uneven subfloor can cause clicking noises, seam separation, edge peaking, and broken locking joints. With hardwood, unevenness can lead to hollow spots, squeaks, lippage between boards, and accelerated finish wear on the high edges. For glue-down installations, low spots can reduce bond strength and high spots can telegraph through the floor and become visible under certain lighting.
The Prep Methods That Actually Fix Flatness
High spots are typically addressed by grinding concrete or sanding/planing wood subfloors. Low spots are corrected with patching compounds for smaller dips or self-leveling underlayment for broader unevenness, followed by feather finishing for smooth transitions. Structural bounce, damaged sheathing, or loose panels require repair and fastening, because no leveling compound fixes movement long-term.
Questions to Ask Before You Sign
What is the manufacturer-required flatness tolerance for my exact product?
How will you measure it (straightedge or laser), and how many locations per room?
What subfloor prep or repair is included in the quote vs billed as additional work?
Will you perform moisture testing (especially on concrete) before installation?
If issues are found, will you document and show the problem areas before proceeding?
When you confirm the tolerance, the measuring method, and the prep plan in writing, you prevent the most common failure modes for both LVP and hardwood. The goal is simple: a floor that stays quiet, tight, and stable because the surface beneath it was prepared correctly.
Wagner Floors evaluates subfloor flatness and moisture and builds prep into a clear plan across Denver, Littleton, Aurora, Parker, and Lakewood, CO. Want a quote that includes the technical checks that keep your floor stable long-term? contact us to schedule a shop-at-home consultation and subfloor evaluation.
