When it comes to preparing a concrete subfloor for flooring installations, there are 3 things to consider: Is it clean? Is it flat? Is it dry?

Cleaning requires pulling up existing flooring materials on the concrete subfloor and removing any and all traces of previously used adhesives, residues, or other build-up from dirt, wax, or oils. Floor sanders or hand held sanders work great for this purpose. You may also be able to get by with just a scraper. Make sure to sweep all the debris, dirt, and dust left over when complete.

If there are cracks or depressed areas, a leveling compound can be used to flatten those areas and provide a smooth surface. This will be important to prevent a floor from potentially separating at the seams. The general rule of thumb is that there should not be a height difference of over 3/16″ for every 10 feet of space. The concrete subfloor doesn’t have to be perfectly level, but it needs to be flat.

The concrete subfloor should be at least a month old to ensure that it is dry. It’s always a good idea to check the moisture level with a meter or other moisture-testing method to know if it is suitable for the flooring product you are using (and type of adhesive to use when installing glue-down floors). If the moisture level exceeds the acceptable level specified by the manufacturer, additional measures will need to be taken or an alternative flooring material will need to be used that is impervious to the moisture.

Photo Credit: Decorative Concrete Kingdom