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Laminate flooring is designed to “float,” which means it can be installed without the use of nails or glue, over virtually any type of subfloor.  The laminate planks are assembled using a strong mechanical locking system to create a beautiful finished floor.

One of the biggest benefits to installing a floating floor is the limited amount of floor preparation needed. The need to remove old floor coverings and adhesives, many of which have asbestos content, can be a real hassle. On large commercial jobs the cost of hiring an asbestos abatement company and bead blasting the concrete may be feasible, but on most residential jobs this is cost prohibitive. In most cases, floating the floor eliminates the need to remove the previous floor. 

This being said, it in no way means that floor preparation is not needed. I have been installing for 38 years and I can count on my hands how many times I have seen a flat floor that does not require prep. First, before deciding not to remove the existing floor, always check to confirm that the finished floor height will not be a problem. Remove the front panel of the dish washer and check for leg adjustment. Locking it in place with the floor could cause some problems. Also check for clearance at the top of the refrigerator. Finding out that it doesn’t fit back into the original space after the floor is installed can also be a problem. 

Most manufacturers recommend that the floor be flat to within 3/16” in a 10 ft. radius. These measurements are consistent with most other types of floor coverings. On floating floors vertical movement needs to be kept to a minimum. I often hear installers complain that it is difficult to determine if prep is needed when carpet is on the floor. I can assure you, floor prep is needed.

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Checking for flatness

I like using a laser level (Photo 1). It’s fast and efficient. I shoot a line to a target with a ¼” scale marked on the face. Then, sliding the target along the floor will indicate areas that require leveling. If the line moves up on the target, the floor has a low spot; if the line moves down, the floor has a high spot. Use a pencil to mark the areas needing attention. You can also use a straight edge. Lay the straight edge on the floor. Three quarters stacked equal 3/16” or use a spacer.  Anywhere that you can slide the spacer or quarters under the straight edge, need fixing. Three planks clicked together make a nice long straight edge (Photo 2).  

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Fixing the floor

In many cases I prefer to sand or grind down the high spots as opposed to bringing the rest of the floor up to meet the high spots. On concrete floors I use a grinder with a diamond wheel (Photo 3). Make sure to use a dust shroud and a vacuum attached. You can trash a house in seconds without it. For low spots, fill with a Portland-based leveling compound.  I recommend using a self drying leveler or patch a day ahead to avoid adding water to the back of the planks, which is a big problem.  Remember, new concrete must cure for a minimum of 60 days prior to testing for moisture.  Cover all concrete sub floors with manufacturers approved vapor retarder.

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Wood sub floors must be structurally sound and deflection free. I like to use a sander or portable planer to take down high areas (Photos 4 and 5). The seams on OSB are always an issue. Remember to set the nails before using the plane. Fill in low spots use patching compounds that are intended for this use. Check the instructions for thickness limitations.

Even though laminate flooring is designed for easy installation, proper floor preparation is necessary to ensure that the installation is done correctly.  You can learn more about installing laminate floors by attending a class at the North American Laminate Flooring Association’s Installer Certification School.  For information, visit