Hardwood floor crowning — middle higher than the edges

The opposite of cupping: each board's centre is proud and its edges drop away. Often you can see the sanding pattern still on the high centres while the edges kept their old finish.

What causes it

In rough order of likelihood. Each one has a tell — the observation that separates it from the others.

1. 1

   A cupped floor that was sanded before it dried

   How to tell: By far the most common cause. The sander took the high edges off while the board was still cupped; when it dried and tried to flatten, the centre became the high point. If the floor was refinished within the last year or two, this is almost certainly it.

2. 2

   The moisture differential reversed

   How to tell: The top of the boards became wetter than the underside — a spill left standing, or wet-mopping a floor whose finish is no longer sealing.

What it actually means

Crowning is usually not a moisture problem you can fix; it is a record of one that was sanded at the wrong time. The wood is now permanently the wrong shape, and you have less thickness left to correct it with.

Mild crowning on a solid floor with wear layer remaining can be sanded flat — once, and only once the moisture has been stable for months. On engineered flooring with a thin wear layer, or a solid floor already sanded two or three times, there is nothing left to take. We will measure the remaining thickness and tell you which case you are in.

• Stabilise humidity at 35–50% and leave the floor alone for a full season before deciding anything.
• Stop wet-mopping entirely. Damp microfibre and a hardwood-specific cleaner only.
• Find out when it was last sanded and how many times. That number decides what is possible.

• Hardwood floor cupping — edges higher than the middle
• Hardwood buckling or lifting off the subfloor
• Black or grey pet stains on hardwood