F46 over anhydrite screed

I looked at a job I have booked in for next week, polyfloor camaro 85m2 in a converted garage.
The builder has put down a new anhydrite screed over underfloor heating pipes.
The anhydrite screed is smooth and dead flat but the builder doesn't want to pay much for prep
My plan is to rub the screed back with a carbon stone machine, Hoover and P121 acrylic then F46.

What do you guys think or recommend?
And what's the correct procedure when dealing with this screed?

Thanks in advanced

 

it wont stick
You'll get top advice on why in the trade section

 

Tell him it needs screeding or walk away mate.
Nothing but problems if you don't screed it.

 

I want to screed it, I would sleep better at night if I did lol
Thanks for advice guys

 

how old/long has the subfloor been down?
thickness?
anhydrite is an evil bugger if you dont treat it right lol

 

Where at cool? Have one to do also, dont want to pay for screed as said finish good enough.

 

mate
You HAVE to screed it, no other option.
And use proper primer, used specifically
horrible stuff, if you dont screed/prepare it properly you WILL be called back to a blown floor

 

Was looking for link in trade section for advice, have been sent guide by f ball on anhydrite. Can you send link please.

 

http://theflooringforum.com/showthread.php?12828-Info-on-Anhydrite-screeds&highlight=anhydrite

Thats just one
just use the search box on top right for anhydrite
Theres loads of posts regarding the horrible bugger lol

 

That's the same response I had lol
Unsure about how long it's down il ask him tomorrow but i have set up hygrometers
It's different thickness in places to get it flat but average 70mm

 

Thanks cool that was very helpful, What sort of grinding are we talking about as I don't have a rotary machine, would a good sander do the job?

 

One company I worked for had no end of problems with these screeds, regular damp tests gave inconsistent results and Lefarge who made the screed recommended a carbide bomb test which I'm sure you know isn't cheap. I actually walked in on a fitter who had latexed 5 apartments with K11 but was unaware the subfloor was anhydrite, when I asked him if he realised it wasn't concrete he said "I noticed it was chalky!!!" lol

The screed blew in all 5 apartments btw!