Heightening wall - Mortar Mix

[AndyJay2019]

Hi all -
Ok so I'm going to give this little project a go myself (yikes).
I need to heighten a low retaining wall (the extra height will not have to retail soil etc.)
I've read about the mortar mix and find different suggestions of 3/1 soft sand to cement and 3/1 sharp sand to cement and a few other suggests of different ratios.
What would be the best sand type, cement, ratios and any additions to the mix?
I've posted a photo to help.
Appreciate any help and wish be luck.

By the way, the wall will be rendered after and capped with some attractive stone (not sure what yet).

Thank you
Andy

 

[^woody^]

4:1 and 3.1 for the coping, or all 3:1 if less than 300mm high. Building sand

A bit of fairy in the mix or buy some plasticiser

 

[AndyJay2019]

Hi Thanks Woody