If you plan to replace carpet with hard-surface flooring, subfloor leveling is almost always required.
Why?
Carpet is very friendly to uneven subfloors.
Carpet is flexible, and also sits on a thick, squishy pad. It has a relatively large tolerance for unevenness in the subfloor; even if you notice flatness issues underfoot, the unevenness won’t likely cause any damage to the carpet.
Hard-surface products generally need a subfloor that is flat to within 1/8″ over a distance of six feet, or 3/16″ over ten feet.
Hard-surface floor products are not nearly as flexible as carpets. If there are flatness issues in the subfloor, such as dips or humps, the flooring planks will ‘bridge’ the empty space underneath when first installed. But the lack of structural support will cause deflection (movement) in the planks every time someone walks over the area, or rolls over it with their desk chair.
Curling
In high-traffic areas where the subfloor is out of flat, rigid-core vinyl planks will deform over time, and before too long, you will start to see cupping/curling. Eventually, the pressure of repeated traffic over the unsupported floor will cause cracking, and the edges will begin to break.
Gapping
With both vinyl floors and floating wood floors, out-of-flat subfloors are likely to cause end-joint gaps. In severe cases, particularly if there is a crack in the subfloor, side-joint gaps can also develop, sometimes running the entire length of the house.
Noise complaints
Underlying gaps between the flooring planks and the subfloor, caused by the subfloor being out of flat, can also lead to noise issues.. In solid hardwood floors and thicker LVP styles, uneven subfloors can cause hollow spots that produce ‘knocking’ sounds when walked over.
Under floating vinyl floors, where plastic moisture barriers are used, excessive unevenness in the subfloor can also lead to a ‘crinkling’ sound, caused by the interaction between the floor’s deflection, the moisture barrier, and the air trapped in the voids between the flooring planks and the subfloor.
Plan for subfloor remediation as part of your renovation project.
The subfloor flatness tolerance for carpeted areas is more generous than the tolerance for hard-surface floors. Additionally, subfloors have a tendency to ‘settle’ over time, leading to even more flatness issues.
When a flooring renovation project involves replacing your carpet with a hard-surface flooring product, the cost of redoing floors must factor in subfloor leveling, considering both the added time and additional financial expense. The upfront cost of a properly prepared subfloor, however, is a necessary component of a successful and durable flooring installation.
