Also (and I've asked this before with no answer) I've never quite understood the need for 'rock hard' floor slabs and the standard use of NHL5 compared with NHL3.5 or even NHL2. A correct mix of any NHL would surely create a strong enough floor slab (providing the sub-base is properly prepared) - after all, the only force to be resisted is compression, something that mortars are very good at. I suppose it could be argued that a 'softer' slab might be less resistant to scuffing or point-load damage, but how many properties have bare slabs? I'd bet they are 99.99% covered with something that would protect from scuffing and other wear-and-tear anyway.
I only mention all this because the whole point of a limecrete slab seems to be breathability yet the 'harder' the NHL grade the less breathable the slab.
