I am doing a complete bathroom reinstall and was planning on using Hardie Backer boards for all four walls (three stud partition walls and one masonry wall). The problem I have is with the masonry wall, which I was planning on using dot and dab to fix the Hardie boards to. Hardie's own website says that dot and dab isn't an appropriate method for fixing to masonry though. The reason I wanted to use dot and dab is primarily because it will make it easier to make the wall plumb (removal of the old dot and dab has meant the masonry wall surface is now quite uneven in places) and also that I need to build the final wall out by a set amount. Some context on the reason why I need to build the finished wall out by a set amount; I am installing some reduced depth fitted furniture against this wall. The tolerance of where the furniture can be in relation to the soil pipe (which is fixed) is wafer thin because of the reduced depth. This means I have this really tight tolerance of where the finished tiled wall surface can be in relation to the soil pipe. So going back to the problem, I don't think I can use Hardie's suggested fixing method (adhesive glue and mechanical fixings) because the finished wall depth would not be enough. I can't add extra tile adhesive to accommodate as this would be more than the maximum recommended. I have seen some posts on this forum saying it is possible to dot and dab Hardie backer, but it doesn't sit right going against manufacturer's recommendations. I have considered building the wall out with studs, but this would then make the finished wall greater than what I need for the reduced depth fitted furniture. Additional info (if useful): Tile backer needs to be strong enough to support large-ish format porcelain tiles (600mm x 1200mm x 9mm) Dimensions for masonry wall are approx 1.2m x 2.4m Ideal finished wall distance from masonry wall needs to be approx 36mm to accommodate reduced depth furniture Anyone have any suggestions or daft things I might not have considered?