Hack of and Re-render, new render showing small cracks.

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B13clark

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Old hotel, render removed, approx 360m2, red grit applied to old, very porous stone walls, plasterers sand from Bradford’s is too gritty, mixing half soft and half sharp sand with hydrated lime and cement, in 3 sand, 1 lime, 1 cement mix, gear is nice to lay on, rule off, float and sponge, not too soft, not too gritty, sponges up and looks spot on, after a couple of days small cracks are appearing.
Could it be the use of the soft sand even though it’s mixed equally with the sharp? Any other suggestions would be appreciated, cheers.
 
Old hotel, render removed, approx 360m2, red grit applied to old, very porous stone walls, plasterers sand from Bradford’s is too gritty, mixing half soft and half sharp sand with hydrated lime and cement, in 3 sand, 1 lime, 1 cement mix, gear is nice to lay on, rule off, float and sponge, not too soft, not too gritty, sponges up and looks spot on, after a couple of days small cracks are appearing.
Could it be the use of the soft sand even though it’s mixed equally with the sharp? Any other suggestions would be appreciated, cheers.
hydrated lime WHY
 
I would say it's the mix...

6 :1:1
Sand cement lime

Would have been a better mix


or


better still forget cement
3:1 sand lime
 
Thanks for the help fellas, it had crossed my mind that I was using too much cement, this hasn’t happened before but I’m glad I asked
 
Old hotel, render removed, approx 360m2, red grit applied to old, very porous stone walls, plasterers sand from Bradford’s is too gritty, mixing half soft and half sharp sand with hydrated lime and cement, in 3 sand, 1 lime, 1 cement mix, gear is nice to lay on, rule off, float and sponge, not too soft, not too gritty, sponges up and looks spot on, after a couple of days small cracks are appearing.
Could it be the use of the soft sand even though it’s mixed equally with the sharp? Any other suggestions would be appreciated, cheers.
What base coat ? Renda grip on stone ?? And not washed sand
 
What's age of building got to do with it? you can get bagged lime renders, bagged s&c, bagged polymer render and you know it's all the right quantities. Price it in to the job its 2019.


People have labourers mixing their cements at all different ratios and wonder why it's failing.
 
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