Hi I have a very old limestone block built house (portland stone) approx 270 years old, it needs repointing I am quite capable of doing this job but I want to get the mortar mix just right I know I need to use lime,sharp sand possibly cement and also has been suggested to use stone dust in the mix but I want to make sure I get the mix just right the house is exposed and does suffer greatly from winds especially in the autumn/winter which when raining really drives the rain in to the house any advice would be greatly appreciated. Thanks
No cement! You'll wreck your house. As I'm always writing on here (purely as a satisfied customer), try this firm: https://www.lime-mortars.co.uk/
We believe you Joe Crushed stone was often added to the sand to give it body, it also adds strength and speeds up setting times,as well as colouring the mortar, sea shells and coal dust were also used
As above. This is the best advice. If you can find a comparison company locally all the better, they will give you the best advice