Reading an anhydrite specification for a Nuneaton plot
Seeing CA-C25-F5 on a plan tells you three things. The CA part names the binder, calcium sulphate. The 25 after the C is how many N/mm2 it withstands when squeezed, and the 5 after the F is its N/mm2 when bent, as classed by the European standard for screed materials. Those figures set the load the floor is designed to take.
At the lower end, CA-C20-F4 belongs in a house where the floor sees light foot traffic. CA-C25-F5 is the middle grade that most homes, flats and offices end up with, and CA-C30-F6 is kept for floors that take heavier punishment. On a Nuneaton new build plot or apartment block the designer normally fixes the grade, and we lay that product and nothing else. Purpose-built flats make up 11% of homes in the town, and their floor drawings are a likely place to meet CA-C25-F5.
You may also find an alpha hemihydrate named on the drawing. Designers pick it when they want quicker drying or a slimmer floor, and its depth and drying times come from its own data sheet, not from the general rules of thumb.
Shrinkage is slight with calcium sulphate, so a large open floor in a Nuneaton apartment block can be poured as wide bays with few joints. Our team works out where the bays and joints fall before pouring, and prepares the insulation, membrane and edge strip underneath at the same time. More on the material itself is in our anhydrite screed guide, and for a site about 4 miles away there is anhydrite flow screed in Hinckley.
Laitance, sanding and moisture tests in Nuneaton
While a calcium sulphate floor cures, a thin, weak skin forms on top. That skin is called laitance, and adhesives and smoothing compounds will not hold to it with any confidence. Once dry, the surface gets sanded down to firm screed underneath and then primed with something formulated for calcium sulphate. Reaching for a cement-type primer or adhesive without checking it suits the material is a common cause of failed tile floors.
A hygrometer, not a hand on the surface, says when it is dry. Flooring brands commonly ask for calcium sulphate to be drier than cement before covering it, so a reading that passes on cement may still be too damp on anhydrite. Look up your flooring maker's own limit. On a heated floor, gentle heat from around day 7 helps bring that reading down sooner.
Water also decides which rooms can have it. Calcium sulphate and lasting damp do not mix. So for a Nuneaton utility, wet room or garage, we would pour a cement based flowing screed instead, or put down a sand and cement floor laid by hand.
Anhydrite & Flow Screed prices in Nuneaton
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 Nuneaton
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 Nuneaton
Nuneaton is about 76.9 miles north-north-west of our Slough base as the crow flies, with postcodes including CV11 and CV10. The nearest towns to it are Bedworth (3 miles), Hinckley (4.2 miles), Earl Shilton (7.4 miles) and Coventry (8.1 miles).
More on anhydrite screed, part of our screeding services.