CA grades and products for Harrow View apartments
Screed materials have a British and European standard, and every calcium sulphate screed carries a designation under it. Within that code, the C figure is compressive strength and the F figure flexural strength, both stated in N/mm2. For a lightly trafficked home, CA-C20-F4 does the job. Most houses, flats and offices fall within CA-C25-F5. Floors that take harder wear get CA-C30-F6.
On developments like Harrow View, the grade appears in the engineer's specification and the screed is poured to exactly that. Some specifications name alpha hemihydrate products instead, used where faster drying or a thinner section matters. Those come with a manufacturer's sheet that sets their depth and drying time, and our pour follows it.
For blocks of flats, the appeal is how little calcium sulphate shrinks. Wide bays go down with hardly any joints, leaving a surface flat enough for thin floor finishes. Because the screed is poured rather than compacted, it also sits evenly over acoustic layers and heating pipes without disturbing them. Doorway thresholds and the borders between heating zones still need joints, which we mark out before the pour.
In Harrow, 9% of homes were built in 2015 or later; before refitting a recent flat, ask the managing agent which grade and product went down. The build-up, from insulation and acoustic layers to edge strip, is prepared by our own team so the screed goes onto a surface we have checked. You get our drying and laitance advice on paper when we finish. To learn more about how calcium sulphate behaves, see our explainer on anhydrite.
Finishing anhydrite floors in Harrow before flooring goes down
Being able to walk across an anhydrite floor does not mean it can take flooring yet. As it dries, laitance forms on the surface, a thin, weak layer that adhesives will not hold to. Once it is dry enough to take the abrasive, that skin is sanded off and a calcium sulphate primer is rolled on.
Moisture needs checking too. Plenty of flooring makers are stricter about moisture on calcium sulphate than they are on cement screeds. A hygrometer test tells you whether the floor meets that limit, so the flooring date is set by a reading rather than a guess. If there is underfloor heating in the floor, it can normally be run to force dry the screed from about day 7.
Keep calcium sulphate out of anywhere that could get wet. A walk-in shower, a wet room, or a plant room that might spring a leak goes in cement based flowing screed instead, or sand and cement packed down by hand. If the base you have needs attention first, that is a floor preparation job. For apartment work next door, see anhydrite screed in Brent.
Anhydrite & Flow Screed prices in Harrow
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 Harrow
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 Harrow
Harrow is about 13.5 miles east-north-east of our Slough base as the crow flies, with postcodes including HA3, HA8, HA1 and HA5. The nearest towns to it are Bushey (3.8 miles), Brent (4.6 miles), Watford (5 miles) and Ealing (5.3 miles).
More on anhydrite screed, part of our screeding services.
