hi been plastering and rendering a few years lately having a problem with render blowing cracking and sometimes top coat appears weak ie easily marked when ladders leant against them i always soak walls first with water use washed plastering sand 4 sand 1 cement use addmixture everbuild 3 in 1 premium waterproofer plasticiser to slow down setting time then soak the scratch coat then apply top coat with 5 sand 1 cement again with add mix as above then float wall and sponge granted last job was on relatively hot day and sun was on wall all afternoon please advise

Are you not using any lime, mate?

no just the 3in 1 admix plasticiser waterproofer & retarder

I usually go 4:1:1 sand, cement, lime for the scratch and 5:1:1/2 sand, cement, lime for the topper.

many thanks is that hydrated lime

probably... have you been down the particle accelerator at cern by any chance?

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http://www.peterborough-plasterer.co.uk/

i use a 3 or 4:1 with waterproofer scratch no need for lime in scratch...
then a 6:1:1 or 8:1:1 float coat... long as the float coat is weaker than the scratch your fine... wont be sandy... leave it a good week between scratch and float coat...

use waterproofer in scratch.... maybe a tiny bit in float coat in summer but not this time of year, the lime does the plasticising...

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http://www.peterborough-plasterer.co.uk/

many thanks is it hydrated lime i need

Get a plasterer in! Rendering is a a tricky thing to do if you dont know what you are doin. It is not a handyman job, because handymen dont really know what they are doing. They are a jack of all trades, not a master of one.

that's not what this forum is about really dave59. as your 1st post you could be a little more helpful to the poster.

Ok. Rendering on a hot day is not advised. I always use a plasticiser/waterproofer/retarder in both coats. You can use an sbr bond which will hold back the suction rate. Apply this before the scratch coat and the final coat. Water it down to 3:1.