Ok.. I am interested on some discussion on how you prep and prime an Anhydrite screed ready for tiling.

What method of sanding do you use , even if the screed is low laitence ..

What method of priming do you do ..

Do you use Acrylic primer or maybe epoxy primer.

Do you use a cement based adhesive or maybe a gypsum based adhesive..

I am interested in how many have tiled to anhydrite and how many have had a failure.


The discussion is basicly to see how many have tiled to one and the way they have done it to see if a majority way is used.

I am gunna ask Alan from lafarge to not input in this discussion as i want an unbiased approach to the results and methods used.


There is an awful lot of conflicting advise on the prep and priming etc..

So please do have your say and input and lets see who does what and uses what..?

Many thanks Dave.

whenever I have tiled on anhydrite we did it in Germany,preparation was sanding of the laitence which had to be done with in 3 days of the screed being laid otherwise the laitence couldnt be removed enough to achieve a good bond with the agregate in the screed ,the sanding was with a rotary machine with grinding blocks attached to the drive board,once ground the floor was left for a further 7-10 days and was then primed with acrylic primer from pci and pci cement based adhesive was used to fix the tiles and grouted with wide joint sanded grout .In wet areas such as commercial kitchens where the floor would be mopped often we used epoxy primer blinded with sand to give a key for the adhesive but often our boss would ask for these type of areas to be screeded with sand and cement as he didnt like anhydrite used in such enviroments,anhydrite screeds were a pleasure to tile on as they were extremely flat and the finished tiling always looked well

Have you done one in the uk Gary..?

i have never done any , but other forums are alway on about them!!

did some apartments last year onto hydrite screed, the contractor. we did it for checked it out to make sure there was no come backs, firstly we made sure the floor was clean ,no plaster snots all over no dust.primed with webber ad250 acrylic primer, adhesive webber rapid flex, grout webber wide joint grout ,had no fails, great to tile on so flat, there was no mention of having to sand down , but there is prob loads of different methods

Also if anybody knows the make of Anhydrite they tiled to... please do mention that aswell.

Originally Posted by Dave

Have you done one in the uk Gary..?

yes ,I tiled some floors at no1 Aldwych Hotel for Euromarble in 1998 the contract was for Ruddy joiney who had the fit out, I told our boss about how to prep the floors and also Ruddy's foreman but they didnt listen and the laitence wasnt sanded soon enough, our boss was using nicobond powdered adhesive and thought that by using their primer and additive that it would get over not doing the prep correctly, lots of the floors failed and it was really tempting to say "I told you so "but in situations like this discovery is the best way of learning for some people, To be fair to Euromarble the bathroom floors were supposed to be in sand and cement screed but the screeders did alot of the bathrooms in anhydrite so they had to pick up from some one elses mistake

So what about primers then..?

This one didn't last long. Come on guys there must have been some anhydrite tiled. We supplied shed loads of the stuff.......

Sorry Dave - will keep me nose out now....

Knew you couldn't resist..

Tiled some anhydrated screeds in salcombe (Devon) over last xmas period
bathroom floors were small areas tiled with porcelanosa polished porcelain. The floors had been cleaned and sanded and tested for moisture by the building contractor the heating had been on and run for 2 weeks and turned off two days before tiling started. The moisture content was then tested just before the primer was applied. The primer was supplied by the building contractor and applied by myself the make of sealer was called maxit. Adhesive was dunlop rapid set single part flexible(cement based) and grouted with bal superflex floor grout.

Kitchen floor was treated the same but as it was tiled in limestone it also had a decoupler installed..