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My terrace is concrete, and would like to lay a tiling (large tiles for outdoor 40X40), but I do not want to put a layer of sand. I was advised to do it with mortar, when do you think?

Slab laying on a sand bed is usually reserved for terraces built directly on the ground. In the presence of a concrete slab, you must seal the tiles with an "adhesive mortar" for the exterior. Sealing on fresh mortar is possible when a screed is installed if the surface is not evenly regular.

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