General Flooring Knowledge, Laminate Flooring, Luxury Vinyl Flooring

Why You Need a Flat Subfloor

Most issues with floating floors are the result of one particular glitch – an uneven subfloor. Having a flat subfloor ensures your floating floor fits well. Although many people assume level subfloors are required under floating floors, the reality is a little more complicated.

The Difference Between Level Subfloor and Flat Subfloor

A level floor may be important in a billiard hall, but you can actually install floating floors onto an unlevel subfloor without a problem (besides having a hard time playing pool in that room). It’s when the floors are uneven that the real issues arise.

Flat and level may seem like the same thing, but a flat floor can be out of level (to a certain degree) and still create a base for comfortable, quiet wood floors.

The easiest way to check the flatness of your subfloor is by using a straight 2×4, about 10 feet long. Lay it on the floor and have a look along the edge resting on the subfloor. This long stretch of wood will uncover any uneven spots, including dips, hills, and gullies. These conditions will create squeaks, groans and bouncy spots.

Typical Problems With Your Floating Floors

You might notice loud and intrusive noises coming from your new floating floors – it could be creaking, squeaking or a hollow knocking sound. All of that racket is the result of uneven floors. When floating floors rest on an uneven surface, and pressure is applied to the top of the flooring, the resulting movement tends to make a noticeable noise. Depending on the type of flooring you have, this sound ranges from high-pitched to deep and hollow. A pronounced bounce can also result from lower spots; the floor gives a little more when walked on, only to bounce back with greater force than spots just inches away. In some cases, the locking mechanism could let go, or even break.

Correcting the Uneven Subfloor

Most manufacturers require that the maximum deflection on a subfloor is 3/16” over a ten-foot span. Any dips and mounds that surpass that amount need to be corrected.

The method of correction depends on the type of subfloor in your home. Concrete subfloors are corrected by screening. This process involves filling in lower spots with fresh concrete and leveling that off to create a smooth, flat area. Wood subfloors, on the other hand, can either be sanded down, or an additional layer of plywood installed, to ensure a flat surface ideal for the installation of floating floors.


It may be a good idea to call in a professional installer if uneven subfloors are a problem in your home. They can be fixed, but it’ll take a fair amount of sweat and the right equipment to handle this initial and essential step. Flat subfloors produce quiet, well laid floating floors. Uneven conditions can be fixed ahead of time, and allow you the greatest enjoyment and value from your flooring investment.

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