Just tore out 800 sf of ceramic tile for installation of laminate flooring. I've spent 2 days on a hammer drill trying to wear down the 30 year old thinset, but there are still quite a few spots remaining. They are eventually worn down and pretty smooth, but still there. Most of them are less than 0.5 mm. How clean does the floor need to be for a floating system?

There are some depots from carpet tack strips. Does it has to be filled?

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  • Ken, please take the tour so you know how to respond to the answers given.
    – isherwood
    Commented Oct 9, 2020 at 17:53

3 Answers 3


One half millimeter seems really small, and well within many of the requirements for flatness from the flooring suppliers. I do not do conversion on the fly very well, but most flooring makers want a floor flat enough so that if you use a good straight edge, any where from 8 to 10 feet long and if you balance the straight edge over a presumed high spot, the straight edge will show no more of a gap that is 1/16" to 1/8", on either end. depending on what you find in the install guide. Flatter is always better, but if your residue is only that thick and setting a straight edge over it, and you see no more that what the install guide calls for, then have at it. It is important to get it flat enough to be with in the guideline for install.

Small "pock marks" left by nails are of no concern as long as they are no larger than a diameter of an inch or two and only at the perimeters of the walls where nobody can tread over them. If they are in the middle of the floor where traffic is, the typical laminate (MDF core) will span over small spots like that, but if it is a thin vinyl laminate, foot traffic will push it into the depression.


Good answers above, but have you considered self leveling compound? That would get things pretty close to flat.

(And if you do go with the concrete grinding, do yourself a favor and get a dust management shroud and a capable vacuum. They make a huge difference.)


I would use an angle grinder with a concrete surfacing disk. These have carbide or diamond embedded blocks and will really clean up high points in a floor. Any bumps will affect the floor and the area around it.

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