Grades and bays for Chichester apartment floors
Calcium sulphate screeds are named by a code set out in the European standard covering screed materials. Read the code as two numbers: C for compressive and F for flexural strength, in N/mm2. A lightly used domestic floor gets by on CA-C20-F4. Homes, apartments and offices mostly take the middle grade, CA-C25-F5. Floors under heavier wear are poured in CA-C30-F6. On a developer's scheme the grade is the structural engineer's call, and we pour that grade exactly, with no substitutes.
Alpha hemihydrate products belong to the same material but form their own group. Specifiers choose them when a thinner section or quicker drying is needed, and every one comes with a product sheet setting its depth and drying, which we follow in place of general rules.
Apartments suit calcium sulphate because it barely shrinks. As it sets it hardly moves, so wide bays go down with few joints. Joints are still cut where a floor needs them, such as at doorways and where one heating zone meets another, and their positions are fixed before the pour.
Conversions are a separate case. At Graylingwell Park, former hospital ward blocks were adapted into apartments, and conversions like that can start with uneven old slabs and need sound separation between flats. The screed then has to work as part of the sound separation between flats, so the build-up is agreed with the designer before the pour. Where the old slab itself needs attention first, see concrete floor repair.
Laitance, sanding and moisture tests in Chichester
Calcium sulphate grows a thin, weak surface skin as it dries, known in the trade as laitance. Adhesive stuck to laitance is stuck to a crust, so the skin is sanded off once the floor is dry enough. A primer made for calcium sulphate then goes on; one designed only for cement will not do.
Moisture is the next check. Flooring makers tend to set the bar lower for moisture in calcium sulphate, and cement screeds are allowed more, so weeks on a programme prove nothing. We test with a hygrometer. A heated floor can normally be force dried by running the heating from about 7 days.
Mixed-use schemes of the kind the Southern Gateway plan covers, between the law courts and the canal basin, often put apartments above ground floor commercial space. Kitchens, plant rooms and wash areas in buildings like those may get wet, and calcium sulphate is not the material there. Those rooms get a flowing screed with a cement binder, or sand and cement laid by hand for the wet areas. For more on the material, see what anhydrite screed is.
Anhydrite & Flow Screed prices in Chichester
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 Chichester
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 Chichester
On the map, Chichester sits south of Slough, about 48.4 miles from our base in a straight line (postcodes including PO19), next to Bognor Regis (6 miles), Emsworth (7 miles), Selsey (7.2 miles) and Havant (9.2 miles).
More on anhydrite screed, part of our screeding services.
