Mortars to use with stone on old houses

Help please!

I have owned an old house is the south of England where we bought proper lime mortar to use with old "soft" bricks to reduce the damage caused by modern cements.

We have just moved to an old mas and some of the stonework seems to have suffered frost damage while the mortar in places looks like hard cement (and none of the mortar seems particularly soft). The house was renovated/extended from the original farm house in the 1970s as we understand it (by a wealthy "household name" family who did not appear to skimp on anything).

Do people use lime-putty based mortars at all in France? What should I try to get and from what sort of builders' merchants?

Many thanks. Alan

The best lime to use is a NHL ( Natural Hydraulic Lime ) not Lime Putty The best NHL are made by St Astier C-E-S-A You will get all the Specs on in English

Be carefull in my experience most builders in France will try and use a HL (Hydraulic Lime) which contains cement OPC or a Pozzalan and tell you it is Lime since it says CHAUX on the bag

Only use a bag marked NHL and do not use Gypsum based products

An NHL 3.5 with a good sharp sand Ratio 2.5/1 will do most work except lime Concrete

Most of the prebagged products contain OPC or other additions

Yep it allows the house to breath most bricos sell it so you don’t need sand. There is somewhere amounts all the blogs a recipe for a good lime render I ink James posted