Timber flooring defects
Engineered Wood Flooring Cupping Over Screed
Boards with raised edges and a dished centre almost always point to a moisture imbalance between the screed and the timber, not a defective floor.
Get your screed moisture tested
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Cupping is when the edges of an engineered board sit proud and the centre dips — run your hand across it and you'll feel the ripple. It's one of the most common complaints we get asked to investigate on floors laid over screed, and it's almost always a moisture-related problem rather than a manufacturing defect.
Wood, even engineered wood with a plywood or HDF core, moves with moisture content. If the screed underneath was still releasing moisture when the floor went down, or if there's an ongoing damp source, the underside of each board absorbs more moisture than the top and swells unevenly — that's cupping.
Below is how we work out where the moisture is coming from, and what needs to happen before a repair floor goes back down.
Moisture limits that matter
≤75% before covering
Cement screed RH limit
≤75% (≤65% under wood)
Anhydrite screed RH limit
8–12% typically
Timber moisture content target
48–72h in room conditions
Acclimatisation period
Common causes of cupping
- Floor covering laid before the screed reached its target moisture reading
- No effective damp-proof membrane between screed and timber
- UFH commissioned too aggressively after the floor was laid
- Boards not acclimatised to room temperature and humidity before fitting
- A leak or rising damp source unrelated to the original screed pour
Cupping vs peaking — what the shape tells you
| Symptom | Likely cause |
|---|---|
| Cupping (edges up) | Underside wetter than top — moisture from below |
| Peaking (edges up, boards pushed together) | Boards expanded with no expansion gap left |
| Gapping (in winter) | Boards dried out — normal seasonal movement |
| Cupping that reverses seasonally | Screed moisture cycling, not a one-off event |
Get your screed moisture tested
Before you lift or replace a cupped floor, let us confirm whether the screed underneath is still the problem.
Before anyone talks about lifting a floor, we want a moisture reading from the screed and, ideally, from the underside of a lifted board. Guessing at the cause wastes money on the wrong fix.
— Exeter Liquid Screeders
Engineered Wood Cupping — questions we get asked
Keep reading across the site
Get your screed moisture tested
Before you lift or replace a cupped floor, let us confirm whether the screed underneath is still the problem.