Different sands for rendering

[Xen]

Hi there,

I've just finished the first layer of render on our garage with a 4:1 ratio of sand to cement with a liquid plasticiser. I used wickes sharp sand for this layer since it said this was suitable for external rendering on the sacks.

I'm now doing the second layer, and want a smoother finish. The thing with the sharp sand was it was very gritty and quite difficult to work with for an amateur

I've just done a test patch using wickes building sand rather than the sharp sand as it is much finer... it applied like a dream, but on the sack it said it was suitable for mortar mix and interior render, didn't mention anything about using it externally. Is there any particular reason why i can't use this externally?

If i can, i would much rather use this since it is much easier to apply and gives a better texture.

 

[marshman]

If the sand is to soft you may get sagging and shrinkage cracks.

 

[Xen]

Thanks for the reply

Is this something that would happen during setting or long-term? I.e. if once its set, the render is still good, can i assume the sand is probably OK to use for the rest of the render?

 

[marshman]

If you put on in any thickness you may have sagging problems and any cracking would be there by the next morning.

 

[Xen]

Great, thanks for the help