Reading the anhydrite spec on Towcester new builds
Calcium sulphate screeds carry a code set by the European screed materials standard. In CA-C25-F5, the CA stands for calcium sulphate, C25 for 25 N/mm2 compressive strength and F5 for 5 N/mm2 flexural strength.
Three grades cover nearly all housing. The lightest, CA-C20-F4, is for domestic floors that see little traffic; CA-C25-F5 is the everyday grade in homes, apartments and offices generally; CA-C30-F6 takes heavier use. For a new build, the engineer picks the grade, and we pour the exact product on the drawings with no substitutes.
The alternative, where a specification names one, is an alpha hemihydrate product. Such products are specified where faster drying or reduced depth matter, and each follows its own product sheet, which we work from rather than from the general rules for the standard grades.
Shrinkage in calcium sulphate is very low, which allows big bays and few joints. That works well for knocked-through ground floors and for apartments. In Towcester, 9% of homes are purpose-built flats, and a whole flat floor can often go down in one pour. Any joints, at thresholds or where heating zones meet, are agreed before pour day.
Our guide anhydrite screed explained has more on the material, and our insulation and membranes service deals with what goes beneath it.
Sanding, priming and testing in Towcester homes
Calcium sulphate forms a surface skin, the laitance, as it dries. It is weak, and adhesives and levelling compounds do not bond to it well. Once the floor has dried enough, that skin is sanded away and the surface primed with a calcium sulphate compatible product.
Moisture is checked before flooring. Flooring manufacturers often allow calcium sulphate less moisture than cement, so a floor that would be dry enough as sand and cement can still be too damp for tiles or LVT. A hygrometer test settles it, and we hand the result over in writing. In a home with underfloor heating, running it from about 7 days can usually force dry the screed.
Homes built from 2000 to 2014 make up 11% of Towcester's stock. When one of them is refitted and the old flooring comes up, the base may turn out to be calcium sulphate, and the same sanding, priming and testing rules apply.
Wet areas are the exception. A wet room or utility floor needs cement instead, either as a flowing screed or as hand-laid sand and cement in Towcester.
Anhydrite & Flow Screed prices in Towcester
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 Towcester
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 Towcester
On the map, Towcester sits north-north-west of Slough, about 44 miles from our base in a straight line (postcodes including NN12), next to Northampton (8.3 miles), Buckingham (9 miles), Brackley (9.5 miles) and Daventry (11.4 miles).
More on anhydrite screed, part of our screeding services.