What's the Best Mix for Perfect Rendering?
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- Опубліковано 11 січ 2018
- Roger helps you get the perfect ratio for your rendering mix.
So, what's the best mix for rendering?
It all depends on what you're rendering on to.
The golden rule is you never make the mix stronger than the material that you're going on to. For example, lightweight concrete block that's 3.6kN, so we don't want a really strong mix for this because if the wall moves, which it will as you always get some expansion and contraction as the seasons change, you don't want the render to be the thing that stops the wall from moving otherwise the render will crack. If you've ever wondered why render cracks, often this is a reason. Also if you put too much cement in the render it shrinks back and it will crack. People don't always believe that, lots of people do a 3:1 mix and say it's nice and strong but that won't stop it from cracking because there's no real tensile strength in it so there's no point putting too much cement in.
Why lime helps make the best mix for rendering
Instead, we make a 6:1:1, which is six parts of sand, one part of cement and one part of hydrated lime. The sand must be plastering sand or rendering sand, not building sand - do not use building sand for rendering because it shrinks and cracks. Sometimes you can add some building sand to the mix for the base coat, but it shouldn't be your primary sand. It's important not to put more than one part lime to one part cement because hydrated lime won't set on its own, you need the cement to help it set. But the lime does give the mix body and make it creamy and gives it a certain amount of elasticity so that if the building moves the render will go with it a bit and if you do get a crack the lime in the mix will move into the crack and re-calcify to some extent. In a way it is self curing and self-rendering. A lot of renderers don't use it and prefer to use plastisier which puts lots of bubbles into the mix which is a good thing but the lime is better as we demonstrate in this video.
Roger also discusses the best weather for rendering.
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#rendering #homeimprovement #diy
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◾ Out of respect to our channel sponsors and the wide variety of people who watch our videos, we'll remove comments that do not follow common standards of politeness and decency. - Навчання та стиль
Too many young builders get caught in the 'brand new transit van and nagging wife for a bigger house' brigade and before they know it they're working 7 days a week and ripping everyone off so they can take their spoilt kids on a dull tour of Disney Land, because their wife thinks they'll like them more. Well here's a message to busy builders everywhere - forget Disney land and a dull pile of plastic presents: buy your kids some second hand books to read as this'll give them the best life imaginable, then work 4 days a week so you can spend time with your family as opposed to throwing sh*t on walls all day while listening to talk sport and talking about talk sport.
Great vid BTW and what a lovely guy. Shows there's a lot of intelligent and articulate builders out there who live a meaningful life and aim to help others. Got some render patches to fix now but I think 5:1 and plasticiser for me.
forbidden forest I don’t know anything about render ratios but you’ve summed up today’s lame mentality perfectly there mate.
we got maybe 5 years left of civilization. A job=wage slave
Well said
Lol so true. But you forgot the VW transporter van thats for work but been lowered and got alloy wheels. And the Fiamma awning on the side that they have never used. Haha
you know nothing john snow
Love the Hawk over the head trick, I used the same with labourers and apprentices for mixing mud for bricklaying. Saved me giving them a clip for making a sloppy batch and they soon learned that if it fell off the trowel over their head, they got it wrong.
This makes my impending job achievable. Thank you.
Another great video, Roger. I have an extension to render, built with high-density, concrete blocks. Mercifully, most of it is glazed but I can see that your advice will make all the difference to the job. I recently completed an en-suite bathroom and your videos were a huge help. Your presentation skills are top notch. Thank you so much for all the help and advice. Truly appreciated.
Wow, after about half a century of doing it my way I have finally found an expert who explains it all so well. I can only say thanks Roger and luckily (?) I have nearly always done any mortar jobs with a 3:1:1 mixture (so I think I am not too far out).
Here in Italy, they are all very vague on the proportions to use but I once contacted the cement company and asked them what they use in a typical 'ready to use' mortar and they told me Sand 71%, Cement 13%, Lime (calce) 16% at the time, which is about a 5:1:1 ratio.
Roger, thank you. You're informative, knowledgable, and entertaining too. I enjoyed and learned from your additional info regarding temperature - living here in a pretty hot climate. Brilliant video production too I should add; not too many, but just Goldilocks effects and editing. I'm about to look up your other Skill Builder videos. Hope you're well mate.
This guy explains in detail better than some lecturers I’ve sat across from
Probably the best rendering video I have seen thanks for the tips
excellent information delivered appropriately with no fluff, thank you very much.
Great detail, superbly presented. Thanks
I like some washed river sand along with some yellow in my scratch coat.
3 : river
2 : yellow
1 : cement
1 : Lime ( or plasticiser, water proofer)
Top coat
5 : yellow
1 : river ( washed & graded)
1 : cement
1 : Lime ( plasticiser/ waterproofer)
Not everyone puts water proofer in the top coat but it works for me.
43 years down the line and no problems yet.
Must say though.Give me a Hydraulic Lime/ River Sand render any day of the week.Beautiful to use, rubs up a treat and looks terrific.
Each to their own I say!!
Love it Roger! This is the video where my SkillBuilder journey began back in lockdown 😂
I'm in the construction industry pal and always looking to learn more and progress, I don't comment on videos often but 2 minutes in and iv already learned somethimg new, thanks for the info mate and keep up the good work ! 👏
Again half way through the vid and iv learned so much, its hard to come by an old school guy like urself that's willing to share the vast amount of knowledge you have as easy as you you do... I'll be subscribing for sure pal... thanks for the info boss 👍 😎
Well done Roger, great tutorial. Cheers
Hi Roger when I was very young as you do we used to just Lime(except cement and sand) for rendering, but it was different than Lime you show on video.
Usually we putted into the hole Lime and mixed it with water and left for few day to get proper consistency and when it becomes like butter we add into every mix and it was brilliant stuff for rendering.
Same we used for bricklaying, just a bit less than for rendering.
Very useful information...simple and comprehensive..
Great video. Really informative for the DIY'er like myself.
Just seen a few of these video's. Excellent. I mean, really excellent.
I love information when it is given rich yet still lends itself to being understood. Great video and explanation, it was easy to watch. 🙂
A friend of mine rendered a concrete block wall for us, he used 60% building sand & 40% washed plastering sand in a 4 to 1 mix, was done ions ago, still perfect, he's been a spread for the last 50 years or so. He didn't use corner beads either, did it freehand, loveley job.
yes a lot of plasterers will chuck in a bit of building sand to make the mix more workable.
Often it can shrink and crack. The other problem is that building sand often has tiny pebbles in it which are a problem in the top coat.
Great video - this will be very useful for me, as a DIY person/occasional user of building materials. Shame about the negative comments, but as usual the people posting them have no videos of their own (I checked), so until they put up videos showcasing their expertise, their coments are worthless.
Thanks Howard, glad to see you're enjoying SB
Very helpful Roger thanks.
Nice video mate very explanatory.
What a great tutorial. Nice one.
Hey Roger, i knew nothing about rendering and followed your mix and application advise exactly,, I was happy wwith the first half wall i did, and after doing 4 half walls my results were almost professional...........thanks so much!!. P.S I remembered a trick from 4 decades ago an amateur plasterer/stucco guy told me; add a capful of dishwashing detergent to the mixture............it makes the render light and fluffy. Too much makes it too light and fluffy though, but it was a very useful tip!
I'm not an expert by any means but I believe washing up liquid / detergent acts as a plasticiser - experts correct me if I'm wrong
Thank you sir, a very big help for me.
Just what Ive been looking for!!
Excellent explanations!
brillant video mate.
Very helpful, thanks!
Thank you for your advice
I’m starting to build a fish pond this summer and want a render finish
I’m using the same block as in this video 👍
Great video really helped me out!!!
Great vid👍🏽
ACTUAL EXPERT....a rare thing nowdays.
and appreciated.
Yes most on sites these days havnt got a clue
Great tip about lime in render, I specify and see so many 1:3 as standard, in books too! Stay safe guv
Hegrewt
At last a video that tells straight away what and why and how much. Brilliant!
Given your body some blood as well 😉
Good vid roger, thanks
Good video, thanks!
I’m learning of you and I appreciate it really
Nice, thanks 🤘
Love it! I've always had problems keeping the muck on the wall, maybe, finally, I'll be able to do it right.
Start small.
Thanks That's the information I needed
Cheers Roger, thanks for the good vids and advice. Building a Pizza oven so needed a bit of info on the render and top coat for the support structure and oven itself. Got a bit of lime also so we are all go. I made fine care not to follow up any of the tosspot replies you have received. Not too many vids from them I see.
Cheers
I have always intended to build an outdoor pizza oven come bar-b-cue but never got round to it. I did some sketches with my son when he was 12 years old and it was going to be our project. He is 32 now.
You are a fantastic help Roger.
Do you ever consider using a hydraulic lime as an additional binder to your sharp sand based mix?
I always find my void ratio in a sand ( its a simple process)
Sharp sand will generally have enough void to acomadate 1 binder to 2.5 or 3 units of aggregate.
6:1:1 is therefore a very good mix.
Although my work is mainly brickwork the mix rule is generally the same.
What are your thoughts on scud coats on celcon type blocks 1st?
I've got a house that's been rendered on to concrete blocks and I've had quite a few long cracks I've had to chop the cracks out and patch them and this time I used plastering sand cement and lime I've been a plasterer for 16 years and the first thing I was taught when floating and rendering was the mix it's important to always put lime in the mix never use building sand I've always done a 5:1:1 mix I hardly render these days but it's fact to much cement and the wrong sand will make your render crack in time
Have a question so iam going to block up a door and window on my extension with breeze blocks what blocks should .I use and will I have to have a different rendering mix for this area to the solid brick area
I love your channel Roger thanks so much
As I have retrain to become a plumber late in life I've just gained so much from your channel particularly
Hi, is it imperative that you have two coats of render (scratch and top) for an exterior wall. I have several 1.5m x 2m sections of wall my neighbour has kindly left me to do! I’ll be growing plants on wires just in front of it all. Any advice would be gratefully received. Thank you and keep up the good work😉
Hi mate
I have an garage to render over lbc heaters, what is the best primer to use before scratch coat or is enough just to water down the wall?
Cheers
Very interesting TY
Simple and straightforward explanation, thank you. One question, with the base coat of 6 parts sand, 1 part cement and some plasticiser, do I add waterproofer as well?
no
So are you saying sand, cement and plasticiser for scratch and sand cement and lime (no plasticiser) for top coat? Cheers
Good one, thanks
Thank you Roger and i`ll take your advices next week down to new zealand. I did read all comments and i still have some days to think about it - what is the "right" mixture between all the opinions.... , and if i don`t fail and my buddy didn`t kill me after our work, well, i`ll give you my feedback. And one thing we do know about it, the sand should not be salty. Anyway, thanx man.
Do I always need scratch and finish coat. I've got a 4m run of plinth about 20cm tall 10-15mm thick and an gonna use some Rendagrip. I normally do two coats but fancy trying it with one coat. Your thoughts?
Thanks for a great video. I am doing a small shed and need to do the inside wall. I bought sand and cement. Question is do you need plasticiser. Is it essential or we can do without it ?
It will make it easier to spread but it is not essential. Just the smallest squirt of washing up liquid will do on an inside wall.
Nice video, you'll always get people slagging you off in the comments saying they've got a better way of doing things. I've done a few videos on my channel and get a few negative comments, I don't mind constructive criticism but I don't like people having a go just for the sake of it. Keep up the good work!!
Thanks Sam. I really don't mind plasterers having a go and encouraging their mates to take a pop. All the comments, good and bad, help the channel. The important thing for me is that people have watched this video and gone on to have a go themselves and a lot of them have been surprised just how easy it is to make a decent job of a small extension or garden wall.
Great video.
Thank you Roger
Good honest advice
Merci pour explication 🙏☺️
brilliant video
Boss I worked for always used buckets to measure sand and cement with - not shovels. This way the mixes are always accurate ratios and the same even colour throughout the job. This also went for mixing brick mortar. Buckets seem cumbersome but you get used to using them. There is an art to using the mixer - keeping it clean and not having stuff stuck on the inside and affecting the next mix. All the best. ...And look after your backs too! (...or you will be sorry... Ha Ha)
Thanks Val, good advice and buckets are the way but hardly anyone has the time, rush, rush.
Correct as a big shovel the lad was using would have made that about 8-1
my Dad had me use a small shovel on the sand and big one on the dust.
Gauge is good for any colour mix
Actually, i find buckets are quicker, i never thought that they would be till i started to use them for consistency... it does depend slightly on your mixers location to the sand if it will be quicker... ... but i find its alot quicker to fill 3 buckets level, and only go to the mixer 3 times than shovel and count 12 times over to the mixer.
less chance of error in counting shovels/better consistency/cleaner site/and can be alot quicker if sand is not close to mixer.
Val Caino Great advice, username and comment!
I've always used bucket's more accurate mix
How do you measure the amount of sand you need to buy? What's the coverage?
Great video! If I took the old render off our garden wall, could I just put new render on, or would it all need repointing first? It's not awful under the render, but the points could be redone. Would the render kill two birds with one stone?
Don't point it. The more dents there are for the render to hang onto the better.
Can you use this method to build a outdoors fireplace ?
I live in Iraq and we use bricks mainly to build our homes I agree with you my contractor has advised me the rendering in winter because cement crazy about water loves hydration.
Best utilize the local material....Iraq....best bricks for 4 thousand years.. the blue and gold bricks of the Ishtar Gate....is something to behold. ;-)
Hi I have a house that was built in the 1950's and the bricks are showing signs of water damage, the faces of a lot of them are crumbling and I want to render them to stop any more problems. I have looked your skill builders but you only show rendering block not bricks is there a difference.
Best quality job
Good job
Hi
Great advise, does it apply to a chimney stack with a liner fitted.
Thanks
Sreve
Yes it does but if it is exposed you may want a slightly stronger mix or some mesh reinforcement to stop it cracking.
Roger seems like such a top bloke!
😛😛😛😛
Good quality video.
in the early 80s i used 1-4 and was criticised for it ? still smile about it now
What is the differecne between building sand and plastering sand? Which one is finer?
good tip man
Great tutorial, really appreciate it. What mix would you use for a base coat on 7neuton block?
Would you recommend using a Weber type top coat?
Thanks in advance
You could comfortably use a 4 to 1 sand and cement but I would put in a 1/2 measure of lime because I like it.
What about waterproofer in the mix?.
For the scratch, you say 6 parts Sand 1 part cement and “a bit of plasticizer”. How much is a bit and what would would be the ratio or part ?
Of we want it to move should we use some kind of resin as the binder instead of cement?
Roger’s the man 👍🏻
Hello Roger, I do like the way you put things across on your videos, always makes a lot of sense. I need to patch a couple of sq, meters of fine textured render on a wall . I will be taking it down to bare (old brick) What materials do I need to carry out this task in the most simple way as I have not done this particular job before? Or can you buy it in a bag ready mixed ? Regards David.
Hi David
You need to buy a bagged render. There are lots to chose from and matching up to existing is always tricky. If you can send some pictures I will try and identify a suitable product.
www.skill-builder.uk/send
So many different opinions on the mix ratio. i am now confused and i want to render a low limestone garden bed
What's with all the hate? 1 part
Hydrated Lime, 1 part Type GP Grey Cement and 6 parts sand by volume seems to be standard here in Oz.
SHARP sand....mostly called Sydney sand here....very important detail....and they DON'T use a lot of lime here...impe.
Thanks!
Thank you so much for helping us to carry on the work.
6:1:1 still a good mix for old red brick walls that need rendering?
I agree with you Roger, I use a 280 liters cement mixer 6 buckets of sharp sand, 1 bucket of cement and one and an half of lime, plaster like you said doesn't need to be bomb or scratch proof, and if the wall is nice and strait use as little plaster as you can because using a lot is a waste of time and material.
Thanks Roger, informative video. Not sure about the parting comment. You will survive lol
thanks mate! Top tips before my DIY disaster
Hi there Rodger, great video, very helpful. I'm going to attempt a little bit of rendering on my side wall and I was Just wondering would you recommend putting pva on first. Seems that some do and some don't. I was told that just giving it a good clean first will do and that pva can stop it breathing. What do you recommend. Thanks
Sorry Alice. I have only just come across this comment. PVA should never be used outside. SBR is way better.
@@SkillBuilder normally you attach beads if you are using beads that is etc.. then skud the walls, then scratch coat aka base coat, then finish coat .
I agree the scratch coat should always be a weaker mix also helps with keeping the walls wet before the finish coat.
I always used a 4 or 5 to 1 for scratch and a 3 to 1 for the finish coat, lime is great for the finish but it can cause bad burns worse than cement if someone has tender skin that is.
Also when using lime let it mix and hold off on the water , this catches alot of people out as it get more watery as it mixes through.
@@philipm1896 if you put a stronger coat on top of a weaker coat it's gonna crack and fall off. I hope you're not a pro
@@iaintait772 building houses 35 years not one has fallen off, guess you are wrong.
@@philipm1896 Hi Philip. I've been rendering houses for about 35 years as well. The only time I might put a stronger mix top coat on might be if I do a thin harl coat on top of the second coat(we're in Scotland) I'm not trying to diss you but it is accepted practice that a stronger top coat on top of a weaker scratch will cause problems. It may be that the addition of lime in your top coat makes it more flexible and less likely to crack but I'm not convinced, but if it works for you then that's good.
well don you . very helpfull . great explanation .top man
Glad it helped
OK The outside of the house has insulation 110mm thick looks and feels like polystrene so how to render and repair cracks ?
I think they render that stuff with a mix containing a polymer sand substitute it's very light and a bit expensive. Not an expert just going on what was happening when next door got external insulation fitted.
Bravo.
Good video , should the Windows not be in before you render ? Or can they go in after ?
You can render up to the corner beads around the windows but the windows then need to go in so you can finish the reveals etc.
If you have put the windows in from the inside it is not a problem to finish the render to some dummy frames.
Great videos Roger, what’s your opinion on the breathability of cement renders ? do you think the lime helps ?
ua-cam.com/video/zcPtcVziiqo/v-deo.html
Thanks Roger, that’s awesome, keep up the good work
Great video - given me the confidence to try patching the broken render myself, save a fortune and feel smug! Thanks!
Exactly the info I needed Roger, thanks yet again. I think the BBC should create a DIY competition series like Bake Off or Sewing Bee and let you be the chief judge !! :O)
That idea was tried 30 years ago on a BBC pilot show I did with Phillip Schofield. It was called The Practically Useful Show quickly dubbed The Practically Useless Show. It was supposed to combine good information with fun but the people taking part badly wanted to win and that killed the fun element stone dead.
@@SkillBuilder That's interesting Roger. I've always felt that you were good 'TV' and surprised we've not seen you on the telly in some way. I've always been a serious DIY'er and last year retired, so can now properly get into those incomplete projects. I'm currently reroofing our place under a 'tin hat' temporary roof that was put up last week. I've discovered that the chimney pots need resetting, hence why I'm here but I assume that I need plastering/rendering sand which is not currently available down her in Eastbourne. Roger, could I use sharp sand for this purpose please? Could I perhaps use a pre mix render ?
Your great ;)
Could you please tell me the best mix for rendering slate stone work on the side of the house exposed to the most extreme prevailing wet winter weather?
I've been plastering all my adult life and agree with everything said here. Only recommendation is that you use should really measure the mix /ratio accurately using a bucket or similar as just using shovels , especially if you have a novice labourer, can go waaaay out.
Hi Rodger , I replace windows and doors in Ireland and my big problem is when plastering reveals overhead with sand and cement outside . The mix keeps falling off . Is there something I can add to the mix to make it stick , or put on the lintel ?
Pleeeeeeaaaassssse help lol
SBR!