What CA grades mean on a Houghton Regis North plot
A calcium sulphate screed designation reads like a code, and it is worth knowing what each part says. Read the C figure as how well it resists crushing and the F figure as how well it resists bending, both quoted in N/mm2.
CA-C20-F4 is the lightest grade, meant for rooms in a home that see little traffic. Most houses, flats and offices are specified one step up, at CA-C25-F5. Where wear will be heavier, CA-C30-F6 is specified. On a Houghton Regis North or Bidwell West drawing, the grade is set by the designer; our job is to supply and pour exactly that, not a near equivalent.
Alpha hemihydrate sits outside that C20 to C30 ladder altogether. Designers pick them when quicker drying or a slimmer layer is needed, and every one has its own data sheet setting depth and drying, which overrides the usual rules of thumb.
What calcium sulphate does well on a new Houghton Regis plot is shrink very little. So a big open-plan ground floor, or a whole level of an apartment block, can go down in large bays broken by very few joints. We still mark out where bays and joints go in advance, with particular care at doorways and above heating circuits.
Flats are a natural fit. 11% of homes in the town are in purpose-built blocks, and apartment floors are a common place for this material because it pumps to upper levels and settles flat. Our guide to anhydrite screed explains more of how it behaves once laid.
Laitance, moisture and primers in Houghton Regis homes
The care after the pour decides whether a calcium sulphate floor performs or fails under the tiles, on a new plot or in an older house.
While it cures, calcium sulphate throws a fragile skin to the surface, known as laitance. It must be removed once the floor is dry, by sanding, or adhesives and primers bond to the laitance rather than the screed. Our floor preparation team handles the sanding.
Moisture testing comes next. A floor covering's moisture limit is frequently tighter for calcium sulphate than for cement, so do not assume a reading that would clear a cement screed is good enough here. We settle it with a hygrometer. On a new plot with pipes in the floor, the heating can normally force dry it from about 7 days, and our page on heated floors covers warming it up.
Priming is the last step. The floor needs a primer compatible with calcium sulphate before cement based tile adhesive or levelling compound goes on.
Keep it out of anywhere that may get wet. For a wet room or a utility outside the house, the pumped option is a cement based flowing mix. For the same material over the boundary, see anhydrite screed in Dunstable.
Anhydrite & Flow Screed prices in Houghton Regis
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 Houghton Regis
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 Houghton Regis
On the map, Houghton Regis sits north of Slough, about 26.4 miles from our base in a straight line (postcodes including LU5), next to Dunstable (1.3 miles), Luton (4.7 miles), Leighton Buzzard (6.1 miles) and Flitwick (6.8 miles).
More on anhydrite screed, part of our screeding services.
