Hi
Yes, our French friend Claud who generally translates for us has said the electrician has a initial run up protocol which needs to adherred to prior to laying the tiles. Plus reference has been made to a primer application that is necessary. I am wondering if this is any way similair the tile addhesive addy you refer to.
dingers
The primer and the adhesive (addy) are separate items and need to be incorporated into any tile installation on any screed. The difference with Calcium Sulphate screeds is the functions that the primer serves. If you select a standard cement based tile adhesive which are admittedly by far the most common available then the primer needs to serve 2 functions.
firstly it needs to "seal" the pore structure at the surface of the screed in order to reduce the level of suction from the adhesive into the screed so that the adhesive does not dry before it has time to set. Secondly the primer needs to form a physical barrier between the adhesive and the screed in order to prevent any chemical interaction between the sulphates in the screed and the cement in the adhesive. This is the bit which catches most tilers out because a standard acrylic primer is not likely to act as a satisaftory barrier unless numerous coats are used. Two is not enough IMO. A much more robust system in this instance would be to use a water dispersible epoxy primer as this serves both functions very effectively.
On the other hand if you select a tile adhesive based on calcium sulphate then there is no risk of chemical incompatibility and you only need the primer to reduce suction which the acrylic primers will do very well.
The attached document might be of some use. It is a translation of the one handed out in France by La Chappe Liquide who supply most of the calcium sulphate screeds over there.
The major difference is the moisture test method which over here is by means of the HAir Hygrometer but in Europe will be by Carbide Bomb test.
