Rendering with lime?



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#1
im doing a rendering job later on in the week, it on a side of a house I've all ways used 4:1 ration of sand and cement. I've been advised to do my next job with a 4:1:1 ratio of sand cement lime and I'm not quiet sure what the lime is if for and would it help me? I've been told it will make it easier for me to work with what are people's thoughts on this? Cheers
 

Deri

Active Member
#2
4:1:1 would be too strong I think. 4:1:1/2 or 5:1:1 or even 6:1:1 would be better. Sand:cement:lime that is.
 

puddove

Private Member
#6
as john --- scratch coat 5:1:1 top coat 6:1:1
the lime makes your mix more workable, and reduces shrinkage cracks :)
 
#16
Ok? Says on the tub don't mix the two and I been told on more than one occasion same thing? But if that's wrong, that's something new I've learnt!
 

BigK

Private Member
#24
What do you mean by 'hold it'?
Your meant to use it without but it's just not workable enough, too raw.
 
#26
I have plenty of rendering experience and you can put freeflo with hydrated lime.
We always scratched with 3/1 with 36 n cement and finished with 6/1/1
The lime makes it more workable and dries nice and light.
Also if it dries in a bit quick it is easier to splash and bring back .
Freeflo shouldn't be used on lime based mixes.
A mix of render isn't lime based its sand based. No freeflo in traditional lime mixes.
In winter add a shovel of lime in the scratch and that will make it pull in quicker!
 

Deri

Active Member
#27
I have plenty of rendering experience and you can put freeflo with hydrated lime.
We always scratched with 3/1 with 36 n cement and finished with 6/1/1
The lime makes it more workable and dries nice and light.
Also if it dries in a bit quick it is easier to splash and bring back .
Freeflo shouldn't be used on lime based mixes.
A mix of render isn't lime based its sand based. No freeflo in traditional lime mixes.
In winter add a shovel of lime in the scratch and that will make it pull in quicker!
That's cleared a lot up!
 
#28
It's a funny old game
I've rendered for years and no what am doing with it.
But haven't had much experience with all the monocouch renders /PAREX/weber/krend
Render is lovely when done right. Quoins keystones all look great.
But you can't get render looking as flat as all of the above
 
#29
It's a funny old game
I've rendered for years and no what am doing with it.
But haven't had much experience with all the monocouch renders /PAREX/weber/krend
Render is lovely when done right. Quoins keystones all look great.
But you can't get render looking as flat as all of the above
Sand and cement still has its place.
 
#31
I don't understand people who say that they don't like rendering/floating in sands & cement, it's the muts nuts!!! I love floating it up and finishing it off with a sponge, rubs -up a treat imo ;)
 

algeeman

Private Member
#32
Haha ratio ??
You mean 20 heaped shovels of sand 50 render 50 brickies sand
1 bag cement
Shovel of lime
Plastiser (fairy).
Waterproof.....nice n fluffy .....
20 tons....fall asleep driving home !!
 
#33
Hi been plastering for 40 years, never had problems with render s&c using 6 & 1 mix with plastersicer. Have used a 6 / 1 /1 cement sand lime mix, which occasionally gets hair line cracking.
 

solway

Active Member
#34
i work/chat/meet with alot of local plasterers around my area and im always curious about their mixes. It drives me nuts when you do a good looking job and its looking good for 6 months and your driving past 1 day after a shower of rain and you notice crazing but when it dries its looking good again and then some jobs never craze at all even though i never use different mixes/ratios.

I think a main culprit of crazing is down to not keeping the finished render moist for 3/4 days after completion or the sun or wind against it in the 1st 3 or 4 days after completion. In all honesty if you turn up to work tomorrow morning and plan to bring down a massive gable and windy/sunny weather is forecast tomorrow or the day after are you to tell your employees "sorry lads but the weather tomorrow is not in our favour,we'll have to go home".

Or else bring down the gable and tomorow send 1 of your employees back to the gable to keep moist all day with the hosepipe(as we all know this will never be allowed for in our prices). So what the f... are we supposed to do. We are always up against it external rendering.

My mix for scratch is always 4 sand to 1 cement(20shovels of certified plastering sand to 1 bag of cement in the big mixer) and plasticiser(used in accordance to manutactures instructions).Wall is always wet down prior to applying render. Id leave it to set/dry/cure for at least 3 days before applying the finish coat.

Finish coat is always mixed 5 sand,1 cement to 1/2 shovel of lime(25 shovels certified plastering sand,1 bag of cement and 2-2.5 shovels of white rhino hydrated lime in the big mixer) with waterproffer(used in accordance to manufactures instructions). Wall is always wet down prior to applying finish coat and if the wall is any way big ill call on the way home from work and wet down the night before once or twice(thats if the rain hasnt wet it already for me) Another problem is keping an eye on the man mixing,making sure he "stays awake".

Anyone who says they never get caught out on a day rendering is talking bull....! On the rare occasion a section of a gable might pull in faster than other areas and its gone too far for sponging id usually sprinkle with water and bring back up again but as iv learnt the hard and embarassing way this is a big no no. Under sills or the first 6-12 inches down from the soffit are areas where render usually pulls in and you could be caught.

Im actually thinking of priming these areas in future now with a watered down sbr mix.

Back to mixes,1 spread whos opinion 1 respect eliminates lime altogether from may to sept/oct in his finish coat. He maintains it causes too much stress on the finish along with sun shine/warm dusty wind etc. I read on here of renderers giving their prefered mixes but usually its just 4to1 scratch and 5/6.1.1 for finish with no mention of plasticiser/w'proffer.

External rendering is a mine field and the substrate has so much to do with it aswell. I'll leave ye with this little story. I have a brother in law who works for a company who make concrete blocks.He is gone from this plant now but when he was working there his job was mixing up the aggregate for the blocks. He had set amounts to put in to the hopper specified by building regulations but on more than 1 occasion the boss man used to walk in the door reach across and reduce the cement content of the mix saying" for f$$$ sake turn that down,do you know the price of cement these days"

All these concrete blocks are meant to be certified. The right mix is used when the inspector from building regulations pays a visit........I rest my case! Happy rendering.
 
#35
im doing a rendering job later on in the week, it on a side of a house I've all ways used 4:1 ration of sand and cement. I've been advised to do my next job with a 4:1:1 ratio of sand cement lime and I'm not quiet sure what the lime is if for and would it help me? I've been told it will make it easier for me to work with what are people's thoughts on this? Cheers
Ello mate
What ever you do don't put to much lime in the mix it will go like crazy paving and look like a loads of shitting crazed paving.