screeding floors

hello.. anyone know if there is a do or dont with floor screeding... i was told to never use bondcrete in a bathroom because it can imulsify due to moisture.. in perth for some reason our bathroom floors are a not very strong mix of concrete like a slab would be.. very sandy mix of sand , cement.. if not sealed properly they become very drummy.. and sometimes crack.. i was taught to use water and general purpose cement to form a slurry and brush on floor then screed with dryish mix 3 or 4 to one cement mix and ram pack floor to level.. now im told to add boncrete to slorry and cement mix.. any idears on hows right or wrong.. or where i can get standards fromm.. people demand guarrentee,s now days and its very costly to go back and fix cracked tiles and drummy floors.. thanks big mac

BC as an admix it is fine but not a bonding product in a wet area.
There are other cross linked products that don't re-emulify.
But dry pack is the best way.

The dry mix is correct, it should be more of a mortar mix as opposed to concrete!

What I have done is water proof – dry mix – water proof again.
2 layers of water proofing may be overkill, but I’d rather be safe than sorry.
Plus the second layer of water proofing prevents the musky or mouldy smells.