Anhydrite specifications for Amersham flats and refurbishments
Purpose-built flats make up 16% of Amersham's homes, and converted flats a further 3%. On floors between homes, the screed usually floats over an acoustic layer, and the specification often calls for a calcium sulphate flowing screed because it spreads evenly over the layer below without being compacted onto it.
The drawings normally name a grade. Expect CA-C25-F5 for most homes, apartments and offices, CA-C20-F4 where a domestic floor sees only light traffic, and CA-C30-F6 if the use is heavier. Reading the code is simple: the C figure is compressive strength and the F figure flexural strength, each given in N/mm2. Some specifiers choose an alpha hemihydrate product to dry faster or go thinner, and then its data sheet sets the rules.
Shrinkage during drying is minimal, so bays can be big and joints few. That suits a long flat floor running from entrance hall to living room. We still plan the bays and joints before pouring, particularly at doorways and changes of shape.
It has one clear limit. A wet room, or any floor open to damp, is the wrong place for calcium sulphate. In those spots we swap to a flowing screed made with cement instead, which we can also supply. Anyone curious how calcium sulphate behaves can read our explainer on anhydrite.
Before flooring goes onto an Amersham anhydrite screed
Three things have to happen before a calcium sulphate screed is ready for flooring, and missing any one of them can lead to the flooring failing.
First, the laitance. As the screed dries, a weak film builds up on top. Sand it away and vacuum up the dust, otherwise adhesive grips that film instead of the screed and lets go. Where more than sanding is needed, we handle it under floor preparation.
Second, moisture. Flooring makers commonly allow calcium sulphate less moisture than cement screed, so take a hygrometer reading and compare it with the figure your flooring maker gives. If pipes run beneath, the heating can usually be switched on from around day 7 to drive moisture out and lower that reading sooner.
Third, priming. Calcium sulphate needs its own primer, applied across the whole floor ahead of any adhesive or compound. If the floor is going to have a thin smoothing layer for vinyl, the floor levelling page explains how that follows. Our written notes on drying and laitance go to you, so the flooring fitter in your Amersham flat knows exactly what went down. If your project is a few miles east instead, the same steps are set out for calcium sulphate floors in Rickmansworth.
Anhydrite & Flow Screed prices in Amersham
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 Amersham
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 Amersham
As the crow flies, our yard in Slough is about 10.1 miles from Amersham, which lies to the north. Postcodes here include HP6 and HP7, and Chesham (1.9 miles), Chorleywood (4 miles), Beaconsfield (4.9 miles) and Berkhamsted (6.2 miles) are close by.
More on anhydrite screed, part of our screeding services.