Preparing anhydrite screed

Hi all, new member here and hopefully a straightforward question.
We are fixing engineered oak to a new anhydrite screed with Sikabond MS. It has been sanded/grinded and the ufh commissioned.
My question is does the screed need to be primed? The sanded surface is quite rough and I would guess quite porous.

Also, the recommended moisture should be 0.3%CM. What would this equate to in %RH measured with a hygrometer box? I am guessing around 55% as 0.5%cm is roughly equivalent to 65%rh.

Many thanks

 

Yes you will defo need a primer


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2 coats


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Thanks Merit. The sika datasheet sYs one is not needed but I was dubious.
Any recommendations, acrylic, epoxy?

 

Acrylic as long as the subfloor is dry


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Dilute first coat , neat second coat

 

Tramex told me that 0.3 was roughly 75% rh, we are waiting on a subfloor to dry to start a karndean installation