Tiling to Anhydrite screeds... A method statement from PCI.

[DHTiling]

Not guilty (I don't think) although I agree that the uncoupling membrane should at least be nominally adhered to prevent rucking and horizontal movement.

Back to the thread though. I am not familiar with primer G although I know it is an acrylic. The first coat being diluted is good practice as this encourages the primer to penetrate into the surface. However you need to be a little carefull in the application as you are "adding" water to the screed which will need time to dry out - I owuld think 24 hours.

I still prefer to see Epoxy Primers with cement based adhesives. whilst water dispersed the way epoxy cures it uses a good proportion of the water in the curing process. Epoxys are also much better at preventing the migration of sulphates so are much more robust against the dreaded ettringite reaction. Of course Gyspum adhesive is even better still at preventing this reaction. I think PCI do a gypsum adhesive in Germany - they certainly do a gypsum leveller.

Other than that PCI seem to have it pretty correct.

That is just the same as using adhesive Alan.. it will get wet.... but as mentioned above.. it does say to leave to dry..between coats.

 

[Stephen@Weber]

Who ever the technical guy is who covers Derby. If you think about it it makes sense if you stick the uncoupling membrane down with a rapid SPF it will defo hold in place whilst you tile it and then if it uncouples after you have tiled it the membrane is doing its job.

I do think if you're going to do it by a more conventional method then an epoxy primer is better once you've removed the smaller particles that come to the surface, at least then you know you've got it covered, with an acyrlic type primer you have to keep soaking it in until its saturated.

 

[Ajax123]

What make of epoxy sealers would you recommend for anhydrated floors and cement based adhesives?

Tremco CS Epoxy (2 coats neat) or Laybond Screedmaster Epoxy (dilute 1:1 with clean water - 1 coat usually sufficient but 2 to be certain) are the ones I usually point people towards. They also serve to make the surface much harder and more stable.