Hi! I'm renovating the kitchen and for starters I'm taking off the plaster and redoing it, this time with a decent mortar backing (bonding was used previously). There's been a bit of damp showing here and there occasionally and I want to sort it out (might just be condensation, not sure, but a couple of the walls are exterior). I want to put something in the mortar to repel damp (keep it from creeping through the brickwork to the inside, if that's where it's coming from), but I'm having trouble finding what's the best additive to use. I was aiming to paint on a layer of a bitumen paint before I put the mortar on (or on a thin layer of it first, to save applying it to a rough brick surface), but apparently that's not a good idea. I came across mention of SBR waterproofer and bonding additive, but I'm not certain it's the best thing for this particular job. It made me think maybe even PVA would do the job just as well, but I don't know. Anyone use it before and can let me know if it's any good? Or even if it's suitable for the job? Or can anyone suggest a better product? Any advice would be helpful, thanks.