external tiling

hi to all who read.

We are currently working on a project using natural slate tiles 600mm x 600mm, we have completed the internal areas on a standard adhesive suitable for this product, but now are continuing through to the external part of this project, basically we are going to be fixing these 600 x600 x 12mm slates onto a concrete surface, the concrete was poured last summer and is 180mm thick with a floated finish, it may need some regulating with a self leveler.

My questions are.
part of me wants to treat thes tiles as thin paving slabs and just lay on a thin sand cement bed.or would this be wrong to do, and if so what is reccomended for self levelling the lowish areas, and what adhesive should i use, also would the sub floor need to have a specific moisture content, and i suppose the grouting , is it the same as the internal grout.
thanks russell

Hi. Fix them using a cement based tile adhesive. tell us what you have used so far and we can help to tell you if thats the right one.

The important thing is to use the solid bed method of fixing instead of a normal notched trowel. A solid bed trowel will either have really big oval notches, or the outer notches will be longer so there is full bed of addy with notches on top. the reason for this is to stop water filling the empty spaces behind the tile, freezing and blowing the fix.

The slab will need to be dry, but how dry depends on the adhesive. most will specify a moisture test first.

same answer to the grout, in many cases its the same, but let us know what you have.

The sealer you'll need is usually different

Thanks for help, so far we have only fixed these tiles internally in a glass walled room, the tiles external are a different entity, I think just a decent tile adesive was used inside, we havent sealed or grouted inside yet but the grout specified is only by colour "Charcoal", the sealant is called Fila stone Plus, this dosent mean a lot to me! I am not the tiler but trying to get a good handle on best way forward.

Thanks
Russell