Reading the grade on a Hemel Hempstead specification
Every calcium sulphate screed is classed for strength under the screed standard shared by Britain and Europe. C stands for compressive strength, F for flexural strength, and each is given in N/mm2. Light domestic traffic calls for CA-C20-F4, the bulk of houses, flats and offices take CA-C25-F5, and floors working harder get CA-C30-F6. If a drawing names one, the screed must meet it; if it names none, we recommend one to suit the building.
Alpha hemihydrate products are a different family within the same material. People pick them for quicker drying or a thinner section, and each one is laid to its own data sheet instead of the general rules.
The growth planned at East Hemel, around 2,500 homes near the M1, and at West Hemel, about 900, is the kind of development where plots and apartment floors can arrive with a calcium sulphate grade already specified. Because it barely shrinks, big bays can go down with few joints, and we set the bays and joints out before the pour to match doorways and heating zones.
There is one firm limit. A shower room, or a plant room with water on the floor, gets cement based flowing screed, since calcium sulphate does not belong anywhere that could get wet. The reason is chemical, and our anhydrite screed guide explains it.
Laitance and moisture before Hemel Hempstead floors are finished
As anhydrite dries, a thin and weak skin known as laitance forms on top. It must come off. After the floor has dried far enough, that skin gets sanded off, the dust is vacuumed and a calcium sulphate primer goes on. Tiles and vinyl that come loose later have often been laid where this step was missed. Where a floor also needs grinding or cleaning before new finishes, see floor preparation.
Moisture is the second test. A screed that would count as dry if it were cement can still be too wet for calcium sulphate, because many flooring makers set the bar lower for it. A hygrometer test tells you where it stands; guessing by colour does not. If heating pipes are in, they can usually be used to force dry it after around 7 days.
Homes built between 2000 and 2014 make up 8% of the stock, and any calcium sulphate floor among them that is re-covered needs the same checks as a new one. If the surface is sound but out of tolerance, levelling compound over anhydrite must use a compatible primer. The same service runs in Watford.
Anhydrite & Flow Screed prices in Hemel Hempstead
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 Hemel Hempstead
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 Hemel Hempstead
Hemel Hempstead is about 17 miles north-north-east of our Slough base as the crow flies, with postcodes including HP1, HP2 and HP3. The nearest towns to it are Berkhamsted (4.5 miles), St Albans (5.7 miles), Harpenden (6.6 miles) and Chesham (6.9 miles).
More on anhydrite screed, part of our screeding services.