A floor can look flat to the naked eye and still contain small hollows or raised areas. With PVC, and especially with adhesive-bonded PVC, such deviations can matter. The question is therefore not whether a floor is perfectly level, but whether it is flat enough for the PVC system chosen.
Flat is not the same as level
A floor can slope slightly across the length of a room and still be flat. Level is about lying horizontally; flatness is about localised deviations such as bumps and hollows. For laying PVC, it is above all that flatness that matters.
Why adhesive-bonded PVC needs a flat floor
Adhesive-bonded PVC is bonded directly. Thin material follows the subfloor and cannot hide irregularities. A small ridge, repair patch or tile joint can therefore become visible later on.
How do you measure flatness?
With a long straightedge or batten you can check in several places and in different directions whether a gap appears underneath or whether the straightedge rocks. For a professional assessment, more precise measuring methods are used.
How many millimetres of deviation are allowed?
There is no meaningful universal figure for this without context. A tolerance always relates to a particular measuring length and to the floor system chosen. So use the instructions of the manufacturer and installer rather than a stray number from the internet.
What if the floor isn't flat enough?
Small, scattered irregularities can often be corrected with a levelling layer. Large differences in level, loose sections or serious cracks call for a different approach first.
How flat does click PVC need to be?
Click PVC also needs a flat base. An underlay can absorb small irregularities, but it is not intended to compensate for substantial hollows or bumps. Excessive deviations can cause movement in, or put strain on, the click joints.
Check the floor before you start
Measure the subfloor before PVC is ordered or laid. That way you know in good time whether levelling is needed, and you avoid having to adjust the flooring schedule once the material is already waiting.