Tiling on anhydrite screed.

[aggy]

Would PVA work to prime an anhydrite screed before tiling on it or does it have to be a specialist ie expensive primer?
It will be in dry rooms so water messing with the PVA will not be an issue. The screed will be sanded etc by the installers.

 

[Richard C]

My advice is DO NOT use standard PVA on any tile base, even in a dry area. Anhydrite screeds must be primed with either an acrylic or SBR based primer to avoid reaction between gypsum in the screed & the cement based adhesive (you should be using for the tiles) leading to tile failure.

It’s not expensive & certainly not as expensive as tile failure; but your call really

 

[aggy]

Ok thanks, no PVA then.
Any particular recommendations for primer?

 

[Richard C]

I use BAL almost exclusively;
http://www.tilefixdirect.com/product/BAPR25.html
or if you need a bonding agent;
http://www.stickwithusltd.co.uk/primer/bond/bal-bond-sbr-primer-1-litre/prod_132.html
but
http://www.pureadhesion.co.uk/mapei-primer-g-water-based-synthetic-resin-1-litre.html
or
http://www.emctilestrade.co.uk/p-Weber_PR360_Liquid_Primer_1Ltr-1266.aspx
or any quality trade product will do. Probably not so critical as with addy & grout but avoid cheap DIY shed products.

 

[aggy]

Thats great, thanks very much for your help.