When can I turn on underfloor heating after screeding?

For anhydrite screed, allow a minimum of 7 days (preferably 21 days) before starting commissioning. For sand:cement screed, the minimum is 21 days. The laitance must be removed from anhydrite before commissioning.

What temperature ramp rate should I use?

Increase the flow temperature by no more than 5°C per day, starting at 25°C. This gradual increase prevents thermal shock and cracking. Once at maximum temperature, hold for at least 3 days.

What moisture level should screed reach before laying flooring?

For tiles on anhydrite: ≤0.5% CM (carbide method). For wood/laminate: ≤1.0% CM or ≤75% RH. Test at multiple locations across the floor, especially in corners and near external walls.

How long does screed commissioning take?

Total commissioning time is typically 40–60 days: 21–40 days initial drying + 4–8 days ramp up + 3 days hold + 4–8 days ramp down. Fast-drying screeds can reduce the initial drying period.

Do I need to commission screed if using electric UFH?

Yes. Any screed over underfloor heating (wet or electric) needs the same commissioning procedure. The screed must be dried out gradually to prevent cracking and ensure proper moisture levels.

TradeCalculator

Heated Screed Commissioning Calculator — Drying & Ramp Schedule

Plan UFH commissioning schedule: initial drying time, temperature ramp (5\u00b0C/day), hold period and residual moisture targets.

Screed Depth

Total screed depth over pipes

Screed Type

Affects drying rate

Max Flow Temperature

System design flow temp

Ambient Temperature

How We Calculate This

This calculator creates a commissioning schedule for underfloor heating in screeded floors, following industry best practice.

The schedule

Initial drying period (no heating)
Start at 25\u00b0C flow temperature
Increase by 5\u00b0C per day
Hold at max temperature for 3 days
Decrease by 5\u00b0C per day to ambient
Test residual moisture

Frequently Asked Questions

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Last updated: March 2026

All calculations are estimates. Verify with your supplier.