It is the cheapest check of the whole project and the most often skipped — until the day the wood floor cups. A screed that feels dry can hide litres of water at its core. Here is the measurement protocol and the thresholds.
The thresholds before covering
| Substrate | Max moisture (CM method) |
|---|---|
| Cement screed / slab | ≤ 3 % (≤ 2 % over underfloor heating per most specifications) |
| Anhydrite screed | ≤ 0.5 % (≤ 0.3 % over underfloor heating) |
The carbide meter protocol (CM method)
Worth knowing
- An electronic pin or capacitive meter gives a surface trend — useful to find the dampest zone, never enough to decide the installation. Only the CM method (carbide) counts contractually.
- Reminder of the delays: cement screed ≈ 1 week per cm up to 4 cm, double beyond; anhydrite also needs its surface skin sanded. Details in screed or levelling compound.
- Underfloor heating: the first heat-up cycle is part of the drying — never lay before the full cycle.
- Compliant substrate = happy wood: the full wood-side protocol is in acclimatisation before installation.