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gilesy

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just for fun.........
why is it that the sand and cement mix is mixed at ratios of 4:1.5:1 or 6:1? how do you find the correct ratio?
old school plasterers should know the answer plus nvq 3 boys or just clever dicks!!
 
the reason you do it that way, is because thats what you were taught. and the reason the bloke who taught you does it that way, is cus thats how he was taught...f**k knows.. ??? ???
 
Everyone does it different personally...I was always taught to do 6:1 in college but since leaving met lot of plasterers who do 4:1-5:1. Next render I do i'm going to do 6:1 7:1:1 and see what happens do you think this will be too weak?
 
gilesy said:
just for fun.........
why is it that the sand and cement mix is mixed at ratios of 4:1.5:1 or 6:1? how do you find the correct ratio?
old school plasterers should know the answer plus nvq 3 boys or just clever dicks!!
Click to expand...

you can find the correct ratio using a shovel or a bucket :) and the ratios are different strengths :)
 
Ive always gauged sand and cement in a bucket level to the top that way render should be the same strength all over and a uniform colour, stronger mix on the scratch, slightly weaker for the top coat. Or just spray OCR simples :)
 
its to do with the backround your rendering onto... for example if you look here https://www.limerenders.com and cick on the lime gauge mix it will show you how its worked out... but when lime renders stopped being used and it changed to cementicios renders it all changed. if rendering with s and c over common bricks they have a weak face so a strong 3 and 1 or 4 and 1 mix could pull the face of the brick off and the render will fail... an engineering brick is much harder so could take this mix no problem but here we have the problen that the smooth brick surface will not provide a key and the render could still pop. new renders all have data sheets telling you what they are suitable for and they are the future... as are lime renders... sand and cement is out dated and not very good in my opinion... dont get me wrong i have rendered and pebbledashed thousands of homes and made a good living... but im all for mono and lime now...
 
Render is mixed of ratios of 4-1 5-1 and 6-1 because it is mixed by labourers and they had to keep the numbers low so it could be counted by hand , to count any higher they would have to take there shoes and socks off slowing the whole process down.
 
FreeD said:
Rendersystems so what mix would you do on common bricks?
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1st coat 5 to 1 second coat 6 to 1 but i would rake out mortar beds also if needed as sand and cement renders and lime renders need a mechanical key for adhesion unlike monocouche renders...
 
My brother chopped two fingers off a couple of years ago , so he has to take his shoes and socks off ::) ::) your right church it really does slow the job down ;) ;) ;)
 
Render Systems said:
FreeD said:
Rendersystems so what mix would you do on common bricks?
Click to expand...

1st coat 5 to 1 second coat 6 to 1 but i would rake out mortar beds also if needed as sand and cement renders and lime renders need a mechanical key for adhesion unlike monocouche renders...
Click to expand...

Mono also requires a mechanical key to help adhesion, hence the need for a pre rend etc
 
warriorupnorth said:
My brother chopped two fingers off a couple of years ago , so he has to take his shoes and socks off ::) ::) your right church it really does slow the job down ;) ;) ;)
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what does he do when theres another variable involved like lime? get his no dont tell me.. ;D
 
Chris W said:
warriorupnorth said:
My brother chopped two fingers off a couple of years ago , so he has to take his shoes and socks off ::) ::) your right church it really does slow the job down ;) ;) ;)
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what does he do when theres another variable involved like lime? get his no dont tell me.. ;D
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Think he's only got one ball so he totaly knackerd ;D ;D
 
warriorupnorth said:
Render Systems said:
FreeD said:
Rendersystems so what mix would you do on common bricks?
Click to expand...

1st coat 5 to 1 second coat 6 to 1 but i would rake out mortar beds also if needed as sand and cement renders and lime renders need a mechanical key for adhesion unlike monocouche renders...
Click to expand...

Mono also requires a mechanical key to help adhesion, hence the need for a pre rend etc
Click to expand...

I have never used pre rend on block or brick work.... what materials are you using?
 
most mono renders require pre rend on low density blocks and brickwork to control suction also it is needed for smooth concrete as warrior says for a mechanical key
 
Render Systems said:
warriorupnorth said:
Render Systems said:
FreeD said:
Rendersystems so what mix would you do on common bricks?
Click to expand...

1st coat 5 to 1 second coat 6 to 1 but i would rake out mortar beds also if needed as sand and cement renders and lime renders need a mechanical key for adhesion unlike monocouche renders...
Click to expand...

Mono also requires a mechanical key to help adhesion, hence the need for a pre rend etc
Click to expand...

I have never used pre rend on block or brick work.... what materials are you using?
Click to expand...

Varied products, i know Parex say just add lanko latex to your first pass an no need for a pre rend, but like merlin says , it controls suction as well as providing a key on low suction back grounds
 
the parex rep near us told us they spec cpi high bond , that lankolatex is a nuisance if your spraying!
 
church said:
yes
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there is a whole chapter in the book on portland cement facades, portland cement was around then and it dose say when it was patented and who by but i cant be arsed reading through to post it. (unless you really want my to)
i think the guy who created it was called joseph aspen!

w miller recomends this ratio and his work is still there today over 100 years later so thats why i use this method, tried and tested mate :)
 
FreeD said:
ESSEXANDY you use a weaker mix? what mix do you use on common bricks?
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It's difficult to say without seeing the bricks as they do vary quite a lot, if working on celcon type blocks I wouldn't use a scratch coat any stronger that 6:1 , the top coat must be weaker and preferably thinner than the scratch coat. The thing is you can go on and on about strength of mixes but if you don't pay attention to making sure it is cured properly then the mix strength is pretty irrelevant, if I use a 7:1:1 mix and make sure it cures well it will have a better strength and crack less than a 4:1 mix just put on and walked away from under a lot of weather conditions.
 
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