Render mix ratio/content ?

[Rotor]

Doing some wall repairs usual render/skim falling away leaving the rough scored finish beneath.
Its not on the house just a outside wall.
How should I mix/ratio the skim coat?
Thanks.

[jeebus]

1 part cement to 4 parts rendering sand, with a bit of waterproofer in there as well if I remember right.

[Rotor]

Great, thanks for that ! I didn't know you could even get Rendering Sand.
P.

[B17NNS]

As said 1:4 will be fine for a general render mix with a dash of waterproofer in the water.

B&Q do a washed plastering sand which rubs up a treat.