2 Coat Ext Render

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Blueboyuk07

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Evening All,
Ok
I have an external render job to do and its for a real picky person so I dont need not even one little crack,
So from all your experiences on here what is the best mix ratio and he wants the top coat hard as to not be marked etc,
Is scratch coat stronger or what,
I've always done 6-1 on both coats as it was the way i was taught

Sean
 
If he dosen't want cracks then hard is not the way to go. As for mixes I alter my mixes depending which substrate I'm working on. What are you working on?
 
Mix as above but with waterproofer in the scratch. If your real worried about cracking a retrarder in the render may help.
SBR I belive is mean to help strenghten render if added to the mix, it also acts as a waterproofer.
 
If they are concrete blocks I'd go with a 4-1 scratch coat with waterproofer and fibres in and a 5-1-1 top coat also with fibres in, use a drop of extra plasticiser if you want but don't use waterproofer in the top coat. Also might be worth thinking about expansion joints if there are any long unbroken runs.
 
essexandy said:
If they are concrete blocks I'd go with a 4-1 scratch coat with waterproofer and fibres in and a 5-1-1 top coat also with fibres in, use a drop of extra plasticiser if you want but don't use waterproofer in the top coat. Also might be worth thinking about expansion joints if there are any long unbroken runs.
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ok im still trying to get my head round S&C...... there's different strengh scratch coats and different admixtures and fibers and different this and put a few drops of this in a splash of that and a bit of lime and some sbr. ahhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh :'( :'(

its just to confusing for me ha ha.... another is problem u all do it different, which dont help either
 
any1 got a gudie i can look at for different mixes for different surfaces please. cheers

or is there a book i can buy with this iformation in it.
 
SkyZOO said:
any1 got a gudie i can look at for different mixes for different surfaces please. cheers

or is there a book i can buy with this iformation in it.
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There is a British Standard book you can buy but it costs a fair bit.
Blueboyuk07 said:
Whats the idea of putting w/proofer in scratch coat, And does the top coat take alright on this and not sag
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I use waterproofer in all my scratch coats and provideing you mix the top coat correctly and don't put it on to thick it shouldn't sag.
 
oh and the only way to get it too iys hardest is to cure properly for 30 days.this means the render shud have a light spray of water at least daily it will cure rock hard
 
Blueboyuk07 said:
Whats the idea of putting w/proofer in scratch coat, And does the top coat take alright on this and not sag
Click to expand...

it evens out the suction in your topcoat, its also mixed stronger then your top coat to reduce cracking.
 
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