We have now removed the 1970's concrete slab in the downstairs loo, and re-positioning the toilet to the outside wall means we don't need the soil pipe crossing the floor. This has restored the floor level down to the original earth floor, which is dry and quite solid, but probably not the best thing for the downstairs toilet. So we need to 'finish' it in some way, without raising the level too much as we're also under the stairs, so head height is compromised to a degree. The adjacent lounge has a slate floor circa 1870 which is 1" thick slate slabs laid on more random slate, with (probably) lime mortar giving an overall thickness of about 120mm. We want to preserve the step down into the loo, so would like to have a finish that is no more than 50mm thick. We could pour a limecrete screed, but I'd quite like to maintain the slate floor theme. Could we just lay thick slate tiles directly on the earth floor? Cost isn't much of an issue as the floor area is really small.

I have a good collection of roofing slates!

<blockquote><cite>Posted By: tony</cite>Single large piece of slate, or resin bond three layers of the slates you have and finish with resin 30mm overall might work.</blockquote>

Do we reckon a single large piece of slate directly onto the earth would be ok? That would be easy to do.

Its about 1200 x 900mm and we need to come up a bit from the soil so 50mm EPS would be viable. Is EPS now considered better than Celotex in this sort of application?

We've decided to use foam tile backing board as it was available in the right dimensions and thickness and, and we're using a dual layer which we feel should then support the 30mm slate floor. Hope fully this will give a good balance between breathability, insulation and strength... time will tell!