Anhydrite grades on new Raunds plots
Its designation, for example CA-C25-F5, comes from the European screed materials standard. The letters and numbers tell the installer exactly what strength the floor must reach. Read C as compressive strength and F as flexural strength, both in N/mm2.
Three grades cover almost every house. Light domestic traffic needs CA-C20-F4, most houses, apartments and offices need CA-C25-F5, and heavier use needs CA-C30-F6. Where a new build plot comes with engineer's drawings, the grade on them is the grade we pour.
On some drawings the screed named is an alpha hemihydrate product. Those products earn their place when drying speed or a slimmer depth counts, and since every one comes with its own product sheet for depth and drying, we pour to that sheet.
As it cures, calcium sulphate barely shrinks. Bays can therefore be large with very few joints, which suits a knocked-through ground floor as much as a flat. Joints go in where they are needed, at doorways or where one heating zone meets another, and the layout of bays and joints is drawn up before the pour. Flats make up 6% of Raunds homes, so here the material is mainly a question for houses and their extensions rather than apartment blocks.
For more background on the material, our anhydrite screed explained guide covers it. If a project needs the screed pumped only, see our screed pumping service.
Laitance, moisture and wet rooms in Raunds
Anhydrite needs attention after the pour. While it dries, laitance, a thin and weak surface layer, forms across the top. Primers and adhesives get no proper grip on laitance, so it gets sanded away when the floor has dried enough, followed by a primer compatible with calcium sulphate.
Moisture testing comes next. For calcium sulphate, flooring makers often set their moisture threshold lower than for cement, so a tile-ready reading on sand and cement can still mean anhydrite is too damp. So on a Raunds floor we go by a hygrometer reading, not by the calendar. If the floor has underfloor heating, switching it on from about 7 days usually helps force the drying along.
Keep calcium sulphate away from floors that might get wet. Put a wet room, walk-in shower or utility floor into cement based flowing screed instead, or into hand-laid sand and cement in Raunds. On a new Raunds house, that often means two materials under one roof, which we plan together so the levels meet.
Anhydrite & Flow Screed prices in Raunds
Liquid flowing screed (which includes anhydrite): £24 to £31 per m² supplied and laid (MyJobQuote, August 2026), so £960 to £1,240 for 40 m². MyJobQuote does not say whether these figures include VAT. See our floor screeding cost guide or screed calculator.
Who lays your anhydrite and flow screed in Raunds
K & B Screeding’s own team, led by director Donatas Bardisevicius. Founded 2019, company 12298780.
See what customers say in our Google reviews and on our testimonials page.
Anhydrite & Flow Screed from Slough to Raunds
As the crow flies, our yard in Slough is about 56.4 miles from Raunds, which lies to the north. Postcodes here include NN9, and Rushden (4.6 miles), Burton Latimer (6.2 miles), Wellingborough (7.3 miles) and Kettering (9 miles) are close by.
More on anhydrite screed, part of our screeding services.
