Converting a period cellar

[a twig]

Ty Mawr are great - https://www.lime.org.uk/catalogsearch/result/?q=Limewash

The shelter coat is great or if you need extra water resistance / coverage - the one with casein in

 

[Cubist]

I would be concerned about painting the floor as this could prevent the floor breathing. This could result in failure of the paint or worse, push damp out toward the walls. I suspect the floor was a later addition to the cellar and may be a poured concrete. Is there any evidence of a Damp Proof Membrane of some sort beneath it? You may find evidence of such, if t exists, where the floor meets the walls.

However, ts feasible that it is a limecrete of some sort over the original earth floor but again it needs to breathe.

Regarding Limewash - TyMawr supply a wide range of lime based products and are based in Brecon - just a few miles down the road from you - they sell pre-mixed lime wash in tubs up to 20 litres but carriage charges for that weight can be high so best go and visit them to collect, you have to pre-order anyway.

 

[Jb72]

Thank you @Cubist