Sometimes the dips in the floor are so severe that it requires removal of the subfloor. Once this is done, repair to the floor joists can be performed. In some instances, these depressions can be filled in with strips of wood that gradate at the beginning and end to blend in with the rest of the floor.

Step 4 – The final step in preparing the sub-flooring is to trim the door casings.

Trim door casings to the same height as the flooring so that the hardwood will slide underneath it and provide a neat and professional look. This can be done with a power jamb saw or even a simple hand saw. Lay some wood scrap on the concrete and cut the casing with the hand saw so that it is flat to the scrap wood.

Step 3 – Fill in any dips or voids in the floor with floor leveling compound.

The floor leveling compound should be quick-setting. Regular cement based products will have problems with moisture later on. A professional will have the experience and will be prepared to lay this down quickly.

The floor leveling compound is mixed into the water in a 5 gallon bucket with a high speed mixer which can be as simple as a paddle type attachment that is attached to a drill. The mixture should have a milkshake consistency.

Once mixed the floor leveling compound is poured onto the floor in small sections, the straight edge of a float trowel is used to flatten and smooth it out. This step is also called “screeding.”

Step 2 – Using a Concrete Grinder to grind down any high levels.

Grind down any bumps or high areas, otherwise you will feel these bumps during installation and it will make installation more difficult. The wood will see-saw. Also the final floor is likely to buckle over time.

A professional will have a heavy duty concrete grinder that will make quick work of these problem areas.

“your final floor will only be as good as your subfloor.”

Step 1 – Checking the floors for flatness. A level is unnecessary. A string line or a straight 2×4 or 2×8 is all that’s needed. The rule of thumbs is that “subfloor tolerances should not exceed 3/16″ of an inch over a 10 foot span.”

Floor preparation includes checking for flatness and looking for loose wood subfloors. It is of the utmost importance to ensure that the subfloor is in sound condition before installing any new hardwood flooring. The floor preparators should check for chunks of drywall mud that might have been left behind and remove it. They should look for anything that will form a void or pocket once the new floors are installed. If the subfloor is not truly flat, then the boards of the new hardwood floor will flex over time resulting in the annoying squeaky floors that we are all familiar with. The floors may also sag over time.

There is no such thing as a true floating floor that underlayment manufacturers claim. There are no shortcuts to proper floor preparation by a professional. An underlayment that promises to correct minor irregularities, will not do so in the long run. Just scraping the floor is not enough.