Specifying anhydrite for Northampton apartments and new plots
Drawings name a calcium sulphate screed by a short code from the European screed standard. Read the figure after C as its crushing (compressive) strength and the figure after F as its bending (flexural) strength, each in N/mm2. Three grades cover most buildings. CA-C20-F4 covers lightly used rooms in a house. CA-C25-F5 fits the majority of houses, flats and offices, while CA-C30-F6 is kept for harder working floors such as busy shared areas.
On an apartment scheme, whether a new block or a converted shoe factory, the grade and depth are set by the designer together with the acoustic build-up. The screed floats on the acoustic layer with a perimeter strip, so it never touches the walls. We pour to the drawings, and we do not substitute a lower grade.
Alpha hemihydrate products are the option where speed or a thinner section matters, such as a conversion where much of the height is taken by the acoustic layer. They follow their own product data sheet, which sets the minimum depth and the drying rate.
Its real selling point is how little it shrinks. Open-plan apartments in a converted factory or new block can therefore be poured in big bays with only a handful of joints. We still mark out where the bays and joints fall ahead of time, at doorways, wherever the room changes shape and along heating zone boundaries.
Homes built between 2000 and 2014 are 12% of the town, and on any plot of that generation or newer, it is worth checking the drawings for a named CA grade before anything else.
Laitance and moisture checks on Northampton anhydrite floors
As anhydrite dries, a fragile film called laitance forms across the top. That film is sanded away before glue, primer or compound touches the floor, and a primer suited to calcium sulphate goes on after. Flooring fixed to laitance is fixed to the weakest layer in the floor.
Moisture limits are tighter than on cement screed. Flooring makers often accept less moisture in anhydrite, so a reading that would let you tile a sand and cement floor can still be too high on this one. Our hygrometer reading is checked against the figure for your chosen flooring. To hurry it along, the heating can normally be run from around day 7, turned up a little at a time.
Keep anhydrite out of rooms that may get wet, because long spells of damp weaken it. A wet room, a walk-in shower or a utility floor where leaks are likely should get a cement based flowing screed, or a Northampton sand and cement floor laid by hand.
Our guide to anhydrite screed covers the material in more depth, and where a dried floor needs a final skim, levelling compound over anhydrite must go on with a matched primer.
Anhydrite & Flow Screed prices in Northampton
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 Northampton
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 Northampton
Northampton is about 49.9 miles north-north-west of our Slough base as the crow flies, with postcodes including NN1, NN3, NN4 and NN2. The nearest towns to it are Towcester (8.3 miles), Wellingborough (9.7 miles), Daventry (11.3 miles) and Burton Latimer (12.6 miles).
More on anhydrite screed, part of our screeding services.
