Calcium sulphate grades for Lewisham Gateway apartment floors
Read the grade as two strength figures. In CA-C25-F5, C25 means a compressive strength of 25 and F5 a flexural strength of 5, both in N/mm2. In a typical house, flat or office, expect CA-C25-F5; CA-C20-F4 covers quiet domestic rooms, and CA-C30-F6 goes in where wear is heavier.
On apartment and townhouse schemes around Lewisham Gateway, Convoys Wharf and Catford, the specification normally sets the grade, depth and build-up. We work to it, prepare the insulation and membrane with our own team, and plan bays and joints before pouring. Because calcium sulphate shrinks very little, big bays with few joints are possible, which helps across open-plan flats.
If the programme needs a quicker dry or the floor has less depth to give, an alpha hemihydrate product may be named instead. They follow their own product data sheet, so drying and heating guidance comes from the manufacturer rather than a general rule. A specifier may pick one for a tight programme or a floor with little height to spare.
Where a floor may get wet in use, such as a plant room, wash area or wet room, calcium sulphate is the wrong material, and a cement based flowing screed takes its place. For a plain explanation of the material, read our anhydrite screed guide; for pumped screeds in general, see the liquid screed page for Lewisham.
Sanding and testing anhydrite floors in Deptford and Catford
Laitance is the name for the fragile film every anhydrite floor ends up with on its surface. When the screed has dried, that film gets sanded off and the dust vacuumed up, and only then can adhesive, primer or smoothing compound go on. Left in place, it can cause tiles and vinyl to lose their bond.
Moisture testing needs care too. The moisture limits that flooring makers allow are often tighter for calcium sulphate than for cement, so a hygrometer figure good enough for tiling onto sand and cement may still be too wet on anhydrite. Pipes in the floor help here: from roughly 7 days, the heating can normally be run to dry the screed faster, which takes time off the wait on a busy Deptford or Catford site.
The primer must be compatible with calcium sulphate, and the flooring contractor should confirm that their adhesive and primer are approved for use on it. You get our drying and laitance notes on paper, so the next trade can see what was done and on which dates.
For calcium sulphate screed in another borough nearby, see anhydrite screed in Newham. If an old concrete floor needs grinding back before a new build-up, our concrete floor grinding service covers that.
Anhydrite & Flow Screed prices in Lewisham
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 Lewisham
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 Lewisham
As the crow flies, our yard in Slough is about 27.5 miles from Lewisham, which lies to the east. Postcodes here include SE26, SE6, SE3 and SE4, and Southwark (3.2 miles), Lambeth (4.2 miles), Greenwich (4.3 miles) and Tower Hamlets (4.9 miles) are close by.
More on anhydrite screed, part of our screeding services.
