Screed Drying Time Calculator

A standard 50mm liquid screed usually needs 8-12 weeks before you can tile over it, and the true green light is a hygrometer moisture test rather than a date on the calendar. This calculator turns your screed type, thickness, and pour season into a realistic drying timeline: when you can walk on it, when you can commission underfloor heating, and when the floor is ready to tile.

Enter your details above and the tool applies the British Standard drying rates for your screed and depth, then flags the moisture test you still have to pass before any flooring goes down.

How screed drying time is worked out

Screed does not dry at a constant rate all the way through. The top layer dries first, then moisture from deeper down has to migrate up through a thickening dry crust, so each extra millimetre takes longer than the last.

For a liquid anhydrite screed the first 40mm dries at about 1mm/day, and every millimetre above 40mm dries at roughly 0.5mm/day. Traditional sand-and-cement screed follows the same pattern with the step at a slightly greater depth: 1mm/day for the first 50mm, then 0.5mm/day for the depth beyond it. Those depths are fixed points from BS 8204, not adjustable settings, which is why the calculator asks for thickness rather than letting you tune the rate.

All of these figures assume good drying conditions: around 20°C, low relative humidity, and steady ventilation. A winter pour dries far more slowly, so the calculator adds a cold-weather penalty when you tell it the screed went down in winter.

Two hold points before the floor is finished

Drying to tiling is not the only wait. Two earlier milestones matter for sequencing the rest of your build.

The first is laitance and light foot traffic. You can usually step onto a liquid screed after 24-48 hours, but that only means it will take your weight. It is nowhere near dry.

The second is underfloor heating. Before you begin the UFH commissioning protocol, wait at least 7 days for anhydrite or 21 days for sand-and-cement. Then ramp the flow temperature up in stages across the following few weeks. Switching the heating straight to full temperature cracks or delaminates the screed.

A worked example

Take a 50mm liquid anhydrite screed poured over underfloor heating in spring. The first 40mm dries at 1mm/day and the last 10mm at 0.5mm/day, and the calculator sums those to the day count shown at the top of the page. That number reflects ideal conditions, but real extensions are draughty and rarely sit at a steady 20°C, which is why the sensible planning window is 8-12 weeks.

Along the way you can walk on it after 24-48 hours, and you can start commissioning the underfloor heating from 7 days. None of that lets you tile early. Book a hygrometer test with your screed specialist and only lay tiles once the reading is below the British Standard threshold. Time is a guide; the moisture reading is the decision.