Is the ducting flush to the rest of the floor. You could need some plywood or latex screeding to sort the levels out.
We use the xtraflor moduleo seal now and then but less then 1mm I’d leave it alone
What date was the main screed laid ? Was the underfloor heating then switched on for 30 days? Did the floorlayer do a moisture test ?
Merry Christmas & Happy new year lads. Hope it’s been a good year for everyone and hopefully a better 2025.
I’d be going 9mm Sp101 plywood, 2 coats of feather on the joints sanding down each coat. or sp101 6mm then a fibre compound
Finished Wednesday , xmas do yesterday. In a world of pain now. We are back in 2nd Jan
Check eBay mate and you might get lucky.
You want a high compression strength so go for Mapei trade plan as not to expensive