Specifying anhydrite for Sunbury-on-Thames conversions and flats
Specifiers describe calcium sulphate with a short code drawn from European rules for screed materials. Read C as crushing (compressive) strength and F as bending (flexural) strength, both given in N/mm2. Lightly used domestic rooms are fine on CA-C20-F4. Ordinary houses, apartments and offices take CA-C25-F5. Harder wearing areas step up a grade, to CA-C30-F6.
In a building converted to flats, the engineer or architect usually names one of these, and we pour that grade rather than a substitute. If a Sunbury conversion is short of depth or time, the specifier may pick an alpha hemihydrate product instead. Depth and drying then follow that manufacturer's own sheet. If a specification is silent on grade, we recommend one in writing based on the rooms, the expected loads and the floor finish, and agree it with the designer before ordering material.
Sunbury-on-Thames has 24% of its homes in purpose-built flats, and flat floors are a good home for calcium sulphate. Shrinkage is slight, so a wide bay laid over acoustic insulation, often with heating as well, needs few joints. Joints that are needed, such as at thresholds or between heating zones, are laid out before the pour.
New building is another fit. Just 8% of Sunbury's homes are 2015 or newer, and new plots like those usually have calcium sulphate written into the design. Our guide on how anhydrite screed behaves goes deeper into the material.
Laitance, moisture tests and wet areas in Sunbury-on-Thames
Drying calcium sulphate grows a fragile surface film, laitance. Glue or compound bonded to that film fails with it, so a sander takes it off first. After sanding a dry floor, we prime it with a product rated for use on calcium sulphate. Some standard primers are not.
Moisture is the next check. A lot of flooring brands demand a drier calcium sulphate floor than a cement one, which means LVT may be refused at a reading that tiles over sand and cement would accept. A hygrometer settles it, measured against your flooring's data sheet rather than a date circled on the calendar. If pipes are in, switching the heating on from about day 7 usually force dries it.
Bathrooms in a conversion are where we draw the line with this material. Anywhere water may linger, such as a shower room or wet room, gets flowing screed with a cement binder or a cement screed packed by hand. Specifiers comparing contractors can also see our anhydrite screed page for Staines-upon-Thames.
Anhydrite & Flow Screed prices in Sunbury-on-Thames
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 Sunbury-on-Thames
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 Sunbury-on-Thames
As the crow flies, our yard in Slough is about 12.5 miles from Sunbury-on-Thames, which lies to the south-east. Postcodes here include TW16 and TW17, and Ashford (2.1 miles), Walton-on-Thames (2.3 miles), Weybridge (3.7 miles) and Chertsey (4.1 miles) are close by.
More on anhydrite screed, part of our screeding services.
