Calling any painter/decorator experienced in listed buildings/limewash.

we had to wait 3 months before decorating after our walls were redone with limewash

the decorator told me not to go with f&b because it's not great, obviously needs to be breathable finish so opted for a paint called earthborn claypaint

Thanks elise.  Grateful for your response.  We are aware of the long lead time before decorating, but the other bit is helpful.  I will check to see if Earthborn do a colour-match. It does not need to be exact but it needs to be pretty close; fortunately it is a pretty basic cream/off white so shouldn't be impossible.

I bought a very old house (non-Listed) in 2011 which was cheap because the previous owners had ruined it by covering the original lime with damp-proofing, gypsum plaster, wallpaper and tiles on the inside, and cement render on the outside. Just to compound the stupidity, everything was insulated, even the bloody loft. Consequently condensation and rain had entered every crack, and been sealed in my the damp-proofing and gypsum, instead of evaporating through the lime plaster and limewash as it had previously.

I hacked the lot off, inside and out, revealing some of the old horsehair-bound lime still there, and had the whole lot replastered and re-rendered with lime. I coloured it with ochre limewash on the outside, and though the mottled effect, as darker patches of rain evaporate away, is almost part of the charm for the exterior, you wouldn't necessarily want the same effect from condensation evaporating on the inside.

So for that I used Dulux Trade Supermatt emulsion. It's water-based, so completely breathable, just like limewash, which is the main thing. It's ever so easy to use and apply, and I'd thoroughly recommend it. Absolutely zero problems with damp in the years since. The colour remains perfectly uniform afterwards.

The only caveat is that, as I said, my house isn't Listed, and I know there are some very odd rules which some inspectors enjoy inventing in that area. But if you can use it, it does the job perfectly both in effectiveness and appearance.

Just seen elise's reply. The other great thing about the paint I described is that you don't have to wait to apply it. The lime plaster carbonates perfectly well underneath it in my experience.

Worth reading:
https://traditionalpainter.com/distemper

Technically, cheapo contractors emulsion, Supermatt and the like are breathable, and are a suitable modern choice as a sealer / wash coat and finish on lime plaster (as well as on modern gypsum plaster surfaces).
So would I use Supermatt emulsion on new lime plaster? On exterior surfaces, definitely not, for reasons of durability. On interior work? I think some heritage-conscious plasterers and restoration folks would probably shoot me if they saw me use supermatt, but would they be right to be so disdainful? From a technical point of view, no, because it works. But if purists wanted the new lime plaster to be painted with lime wash, as in days of yore, then any emulsion would prevent the walls from ever being over-painted with lime-wash.

screaming - Thank you, this too is very useful.  I don't want to go into too much detail, but the rest of the interior of the building is also lime plaster, and was previous decorated with Dulux Trade Emulsion. This paint was specified by a previous architect!!!.  Our new architect is not going to prescribe limewash although it is his preference.  The advantage of your proposal is that we can exact match the colour.  Not doubting you, but I will need to check your breathability claim.  Very many thanks.
bb

Quite right to do your own research.

I'll just say that it's the water base which ensures its breathability. You paint it on, the water evaporates and the pigment left behind provides the colour. The pigment is essentially a powder, so moisture evaporates through the gaps between the grains.

Vinyl emulsions, on the other hand, have an oil base. And oil does not evaporate when you paint it on. Instead it dries out to a solid, impermeable coat which traps moisture in the wall, and the paint blisters and the wall eventually crumbles.

The advantage of vinyl emulsions is that you can wipe them clean, which you CAN do with water-based ones, but you have to be gentle. On the other hand, touching up any blemishes with water-based emulsions is so ridiculously quick and easy that it's hardly an issue. Open the tub, dip in a brush, paint over the affected area and rinse the brush clean under the tap. And that's it. Within a few hours, depending on drying temperature, you won't be able to tell the difference.

Also used Earthborn.  Quality stuff.  Your local paint merchant should be able to knock up the colour that you need by mixing existing colours.

Vinyl emulsions are water based too screaming

jamesdean - Most emulsions ARE waterbased, but we have been warned/advised off vinyl/acrylic emulsions because of their poor breathability.