Calcium sulphate grades on Harlow apartments and plots
Each calcium sulphate grade is a strength rating. Read CA-C30-F6 as calcium sulphate rated at 30 N/mm2 compressive and 6 N/mm2 flexural strength, in the European standard for screeds.
The grades line up with the use of the floor. For lightly used rooms at home, CA-C20-F4 is enough. CA-C25-F5 is what most Harlow houses, flats and offices end up with on paper. The busiest floors go up to CA-C30-F6. Alpha hemihydrate products are a separate case: they come in where drying speed or a shallower floor matters, and each one is laid to its own data sheet.
On an apartment floor the material has clear benefits. Because it barely shrinks, an open-plan Harlow flat can be poured in large bays that need very few joints. Insulation and heating pipes underneath are no problem for it either. The bay and joint layout still needs planning before the pour, particularly at doorways, corridors and where the floor narrows.
Only 6% of Harlow's homes were built between 2000 and 2014, and more new build plots are to come, with permission for homes at Gilston granted in 2025. On those plots, the architect's specification sets the grade and depth, and we pour to it.
For what calcium sulphate is and how it differs chemically from cement, read our anhydrite screed guide. Pipe cover and commissioning for heated floors are covered on our Harlow underfloor heating screed page.
Sanding, testing and priming Harlow anhydrite floors
Every calcium sulphate floor needs finishing work before flooring. While it sets, laitance, a weak and powdery skin, gathers on the surface. After drying, we sand that skin away and clear the dust; leave it and neither adhesive nor compound will hold. That sanding is part of our preparation work before flooring. Then we prime it with something designed for calcium sulphate.
Moisture needs checking with a hygrometer, and we compare the reading with the flooring maker's own limit for that product rather than a general rule of thumb. Flooring makers frequently allow calcium sulphate less moisture than cement, so a Harlow flat floor that would pass as cement may still need more time. Where pipes are fitted, running the heating gently from around a week in normally speeds things up.
Calcium sulphate is the wrong choice for any room where water may end up on the floor. For bathrooms with level access showers, utility rooms and plant rooms, a cement based flowing screed is used instead, and this decision belongs at the specification stage.
Specifying the same material for Hertford? Our Hertford anhydrite page covers it.
Anhydrite & Flow Screed prices in Harlow
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 Harlow
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 Harlow
On the map, Harlow sits east-north-east of Slough, about 35.8 miles from our base in a straight line (postcodes including CM20, CM18, CM17 and CM19), next to Sawbridgeworth (3.8 miles), Hoddesdon (4.7 miles), Epping (4.9 miles) and Ware (6.4 miles).
More on anhydrite screed, part of our screeding services.
