Anhydrite grades for flats and new blocks in Hackney
Look at the screed note on an architect's drawing and you will find a code like CA-C20-F4. Its C value gives compressive strength and its F value flexural strength, measured in N/mm2. That CA-C20-F4 grade is for lightly trafficked domestic rooms; a step up, CA-C25-F5, covers most houses, apartments and offices, and CA-C30-F6 is kept for harder wear. Whatever grade the drawing names is the grade we pour.
Some specifiers go for an alpha hemihydrate product. They are picked where faster drying or a reduced depth matters, which can be decisive in a conversion with tight floor heights, and each one follows its own product sheet.
Calcium sulphate earns its place through low shrinkage. Bays can be large, joints are fewer, and a long open-plan flat can be poured without the joint pattern a cement screed would need. We still mark out bays and joints ahead of the pour, at each threshold and wherever one heating zone meets another.
Warehouses being turned into flats and new blocks going up add to the number of apartment floors in the borough. In a new block, the screed usually floats on an acoustic or insulation layer, isolated from the walls by a continuous edge strip.
Not every floor suits it. Anywhere water can sit on the floor calls for a flowing screed based on cement instead, and a small wet room can be hand-laid in sand and cement to falls.
Sanding, testing and priming Hackney anhydrite floors
Once the screed has dried enough, its surface laitance has to go. This thin, weak skin forms as calcium sulphate dries, and adhesives do not hold to it reliably. So we sand it back, clear the dust and apply a primer suited to calcium sulphate, and only then can tile, LVT or wood adhesive go on.
Moisture testing follows its own rules. Plenty of flooring makers allow less moisture in calcium sulphate than in cement, so the hygrometer has to read below the calcium sulphate figure; passing the cement one is not enough. With underfloor heating fitted, force drying can usually begin from about 7 days after the pour; the warm-up itself is described on our Hackney underfloor heating screed page.
In a flat that someone wants to move into, it is tempting to lay flooring as soon as the floor looks dry. That is where problems start. We give drying and laitance advice in writing on handover, so the flooring fitter can see exactly where the floor stands.
For how the screed reaches the flat in the first place, see pumping liquid screed into Hackney blocks. Our anhydrite screed guide goes further into what the material is and how it behaves.
Anhydrite & Flow Screed prices in Hackney
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 Hackney
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 Hackney
Hackney is about 25.1 miles east of our Slough base as the crow flies, with postcodes including N4, E5, N16 and E8. The nearest towns to it are Islington (2.1 miles), Tower Hamlets (2.5 miles), Haringey (3.5 miles) and Camden (3.8 miles).
More on anhydrite screed, part of our screeding services.