For an installation to last, the substrate needs to be structurally sound, and also plumb and true. If the substrate has small cracks in it, these can usually be controlled by a crack suppression membrane.
If there is any doubt about wall, floor, or building integrity, consult an engineer for an assessment.
Modified thinset on cement fibre wallboard is a simple alternative to a mud-pack ( thick cement bed) substrate method. It is also a tested substrate for large format glass tiles: larger tiles are more prone to cracking when an underlying cement bed shrinks.
NEXT
