Rendering ratio problems

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James1905

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Hi new to the site but I'm a plasterer

ive rendered a garage it was a mix of concrete blocks and thermalite blocks a layer of each right to the top . The render has actually blown from the wall all over I used the ratio 3:1 for scratch and 4:1 for top coat the client has phoned the cement company which it came from they recommended SBR the whole wall then scratch it and after cover it with a sheet and keep damp for 24 hours using a mix ratio of 7:1 then 8:1 this seems to me far to of a weak mix for this kind of work and been using the 3:1 and 4:1 mix since I started with no problems . Does anyone know any reason why this render has blown ??????
 
For a mix of blocks, I work to the weakest block, yes I would splatter coat a mix of sloppy sand cement with sbr in the water, mix your sbr 3/1 with water been the 3 ,mix sand cement very sloppy 3/1 sand cement with this sbr water, splatter this on ,leave for a day, mix a render coat 6/1 sand to cement, put two handful of render fibres in the mix ,use waterproofer but carefully ratio it to the instructions on the can, keep the scratch damp for a week. Then mix a second coat 6/1/1 sand cement lime, put one hand ful of fibres per mix in this, keep it damp when finished to stop rapid drying.
 
Thanx for all you help !! I can't believe I've only had this problem after 10 years of plastering !! When you say mesh you are talking about stainless steal EML yeah ? Sounds like its my fault then I will have to go put it right :-(
 
James1905 said:
Thanx for all you help !! I can't believe I've only had this problem after 10 years of plastering !! When you say mesh you are talking about stainless steal EML yeah ? Sounds like its my fault then I will have to go put it right :-(
Click to expand...
No plastic render mesh that we use in external modern renders..
 
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