What anhydrite actually is
Anhydrite screed is bound with calcium sulphate rather than cement. On Devon drawings you'll mostly see it called up by brand — Gyvlon from Anhydritec, or Gypsol. It arrives as a fluid, finds its own level, and wraps tightly around heating pipework without the voids a hand-tamped sand and cement floor can leave.
Because it barely shrinks, a big open-plan ground floor can go down without bay joints. And per cubic metre it usually costs less than the cement-based alternatives, which matters on a large extension where the depth adds up.
Rooms it suits in an Exeter house
Think bedrooms, lounges, hallways and kitchen-diners in a new build or extension with wet underfloor heating. It's strong on thermal conductivity, so the heat reaches the room quickly. It's also comfortable at deeper pours of 50–80mm, where a cement mix would ask for more curing time. Engineered boards or LVT on foam underlay sit happily on top.
Where we'll talk you out of it
Gypsum doesn't like being wet again and again. For a wet room, a power-shower en-suite, a basement over a doubtful membrane, or a floor getting an epoxy or polished finish, we'd point you to the cement based liquid screed instead. Put anhydrite in a wet room and you'll be back in a year to lift it.
Our pour sequence
- Perimeter foam fixed, polythene membrane taped, heating loops pressure-tested and clipped.
- Laser datum pins pushed through the insulation to true finished level.
- Static mixer on the drive, hose run through the house — 20–40m³ in a pour is normal.
- Two dappling passes to break the surface tension, then a spike roller to let the air out.
- 48 hours with nobody on it, then steady drying. The laitance is sanded off before any adhesive.
Timing your tiler
A 50mm anhydrite floor is usually ready for tile in three to four weeks, depending on the weather and ventilation. We don't guess — we take a moisture reading and hand you a signed-off figure. Build the sanding step into the programme; it's routine, not optional.
Still weighing it up? The full technical write-up lives on our anhydrite screed service page, and screed floor installation in Exeter covers prices and survey.