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What's the Best Mix for Perfect Rendering?
Рет қаралды 633,046
Күн бұрынRoger 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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@forbiddenforest5327 5 жыл бұрын
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.
@steveblack610 5 жыл бұрын
forbidden forest I don’t know anything about render ratios but you’ve summed up today’s lame mentality perfectly there mate.
@voidisyinyangvoidisyinyang885 5 жыл бұрын
we got maybe 5 years left of civilization. A job=wage slave
@JAY-xg4se 5 жыл бұрын
Well said
@Bish186 5 жыл бұрын
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
@puremoore 5 жыл бұрын
you know nothing john snow
@baretteroyce5120 Жыл бұрын
This guy explains in detail better than some lecturers I’ve sat across from
@brianobrain8985 Жыл бұрын
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.
@321357w 5 жыл бұрын
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.
@martineleven8179 5 жыл бұрын
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.
@SkillBuilder 5 жыл бұрын
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.
@cementhapavery 6 жыл бұрын
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)
@SkillBuilder 6 жыл бұрын
Thanks Val, good advice and buckets are the way but hardly anyone has the time, rush, rush.
@theessexhunter1305 6 жыл бұрын
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
@aaronstately 6 жыл бұрын
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.
@jewelcitizen2567 5 жыл бұрын
Val Caino Great advice, username and comment!
@raymondkirkham3815 5 жыл бұрын
I've always used bucket's more accurate mix
@MARKMANIATT 5 жыл бұрын
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!!
@dnimon936 3 жыл бұрын
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!
@brucehazelton4393 2 жыл бұрын
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
@adamgarrett3646 2 жыл бұрын
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 ! 👏
@adamgarrett3646 2 жыл бұрын
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 👍 😎
@neilsmith9473 4 жыл бұрын
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.
@ParaBellum2024 5 жыл бұрын
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.
@SkillBuilder 5 жыл бұрын
Thanks Howard, glad to see you're enjoying SB
@jaimaraj4059 5 жыл бұрын
This makes my impending job achievable. Thank you.
@sherrieholland9765 2 жыл бұрын
Probably the best rendering video I have seen thanks for the tips
@ron1martens 4 жыл бұрын
I once had to do a repair job for a builder which had some serious cracking. So I called a consultant who put me into touch with an industrial chemist. I then worked on using plaster without lime and rendering or even mortar without lime. The industrial chemist stated. We consider lime to be no good. I thought okay. It was the best thing I even did. So what I'm saying if you use lime then you make the strength of the mortar according to the strength of the substance you are putting it on. Exactly what you mentioned. However, with the product I use you can mix whatever strength you like to a certain extent. And I think there are many factors to take into consideration. I use what is called a latex rubberised synthetic emulsion system. If you render onto old bricks which were laid without cement then you will get surface retention. So you will see a certain amount of cracking as the compression is very low opposed to bricks laid with cement in the mortar. Without lime I can wash my tools without wearing rubber gloves. Also if some material splashes in my eyes I don't need to race to the water to get the mortar or plaster mixed with lime put. Lime is highly corrosive so if it gets on aluminium it anodises. Although cement had alkaline and can sometimes leave a mark on specially coated windows glass. I found that out with a client when some mortar got in behind covered up windows. This is partly due to cement manufacturers cutting costs and leaving out gypsum which in the last we had better cement than from recent times. I'm not sure about U.K. Because I'm from Australia. I think of you use plasticisers then perhaps also use some bonding agent. I use an addicrete add mixture which is a plant based material which also is a water proofer. That combined with the rubbberised emulsion system really makes a great mix and you will never go back using lime. Trust me. It also has a stronger finish and reduces efflorescence. Anyway great video.
@SkillBuilder 4 жыл бұрын
There is a lot to consider here. I think you might be talking about SBR but I am not sure. Can you send some product details so we can look at the spec? It would be great to develop this discussion.
@ron1martens 4 жыл бұрын
Skill Builder thanks for the reply. Check out calmarc chemicals based not far from where I live. The product I'm talking about is screedbond. It is rather expensive and I have had many discussions with Jeffrey consulting his products and working with the plaster so give it trowel slide. Here is the link. www.calmarc.com/ Plaster I worked with Jeffrey and there are only a few of us in the whole state that worked out the method to use this product. Thankfully I listened to plasterers from UK who stated get the plaster on, trowel it smooth and let it go hard before giving final trowel. The product gets very hard and does not draw fat so making a small batch to fill in voids achieves a more desirable finish. Also I use a fine spray to spread the material. www.calmarc.com/gypsum-plaster-finishes.html Screedbond www.calmarc.com/adhesives.html In this screedbond is a data sheet within. Jeffrey stated the screedbond can be used to make tile adhesive mixed with cement. I have also patched timber at 2/1 sand cement ratio with screedbond 50/ 50. I recently did a cement dado 50%'water 50%'screedbond. It hasn't cracked yet so I will keep an eye on it. The cement mortar wasn't too strong either. That's what I was amazed with. It's like throwing the rule book away. Mind you the lime industries don't like it. Cheers. Keep up your great video. Yourself and Robin Specialists in your field. Oh the cement dado I mixed I made one mix 2.8 fine .3mm silica sand to 1 cement also adding addicrete p. The second mix I made 2.5 /1 all 50/50 water screedbond. I found the 2.8 to one better mix. Normally cement dado is 1 cement 1 lime and 1.5 sand. You get lots of cracking. I did a small screed on top of smooth concrete upon advice from Jeffrey. Since the results were rather pleasing I decided to do the mix of cement dado. I plan to actually polish with a wet concrete polisher.
@MsSimpledesign 5 жыл бұрын
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.
@scottleft3672 4 жыл бұрын
SHARP sand....mostly called Sydney sand here....very important detail....and they DON'T use a lot of lime here...impe.
@mervynhardy3693 11 ай бұрын
65 years ago when I began to serve my time one of the first things I was told as a right hander,always work from left to right. You usually can spot a plasterer by how he uses his hardboard and TROWEL,it's never called a float. A float is made from straight grain wood(yellow pine if possible).
@Lemon-squeezer 5 жыл бұрын
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
@edknoxwill520 5 жыл бұрын
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.
@cglees 3 жыл бұрын
Love it Roger! This is the video where my SkillBuilder journey began back in lockdown 😂
@randymarsh3636 3 жыл бұрын
I personally go any less than 4-1 on a scratch unless the masonry was very soft.
@scottleft3672 4 жыл бұрын
ACTUAL EXPERT....a rare thing nowdays. and appreciated.
@MrAdeyb 3 жыл бұрын
Yes most on sites these days havnt got a clue
@SamDaviesBuilder 4 жыл бұрын
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!!
@SkillBuilder 4 жыл бұрын
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.
@Vincentofvega Жыл бұрын
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.
@francobarone7437 6 жыл бұрын
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.
@TheNixbrix 5 жыл бұрын
in the early 80s i used 1-4 and was criticised for it ? still smile about it now
@davidh2191 2 жыл бұрын
Scratch 4:1 sand cement with waterproofer and plasticiser Top coat 6:1;1 . Sand , cement @ hydrated lime , no plasticiser as the lime helps with workability
@queenslander954 3 жыл бұрын
We hose the walls down soaking wet in summer down in Oz , he’s right it stops the cracks & also gos off slower.
@marcinmioduszewski1456 2 жыл бұрын
I’m learning of you and I appreciate it really
@JakeBM4 5 жыл бұрын
Roger seems like such a top bloke!
@harryedwards9391 5 жыл бұрын
😛😛😛😛
@nikolaosbouloudas368 2 жыл бұрын
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.
@cocoamcjaegermeister5534 2 жыл бұрын
I love information when it is given rich yet still lends itself to being understood. Great video and explanation, it was easy to watch. 🙂
@adamzaloga9679 3 жыл бұрын
excellent information delivered appropriately with no fluff, thank you very much.
@Ahmed12529 5 жыл бұрын
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.
@scottleft3672 4 жыл бұрын
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. ;-)
@ronrocha316 3 жыл бұрын
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 ?
@petergambier 6 жыл бұрын
I rarely use cement as I specialize in lime mortars and plasters and tend to slake my own lime putty and use it because there is much less wastage and I find it a lot stickier. The 6:1:1 is a good mix, the hydrated makes a good plasticizer and is preferable to using febmix I found. On my own place I have 5 different backgrounds that I lime rendered: Rubble-stone, cob, old 1970's brick work and 2 types of blockwork, the thermalite and the denser concrete block. The blockwork was less preferable to the other backgrounds and I found more cracking than on the other area's where there are hardly any. You shouldn't really use lime on new builds because it's pointless, the cavity wall structures were designed for cement mortars and never use cement on old builds this is why there are so many issues with wood rotting, moisture retention and salt build-ups etc, cement render traps it all in, old lime mortar builds need new lime mortar for pointing or rendering. My prefered lime putty mortar is 3:1 ( 2 & 1/2 sharp angular sand and half a builders sand or a stone dust to one putty or an hydraulic). Some folks use putty and an NHL but I use one or the other, never both together, but as I said, with a putty mortar there is less wastage because you can scrape it off the floor and use it later. Hot mixes are another matter and work better I think but thats a whole new ball game. I saw a film where some old lime pits were found in Italy, the lime putty was about 400 years old and it was still usable because lime putty starts to set when exposed to air and hydraulic and hydrated sets when exposed to the air, also bags of NHL have a shelf life of about 3 to 4 months although I have used bags that are about a year old. This is one of the reasons I prefer the putty mixes, less goes to landfill. As you said, don't ever have a stronger mix than the background. Happy building Roger.
@SkillBuilder 6 жыл бұрын
Great comment Peter. Lots to think about there and we will look at lime mortars when we get a chance.
@petergambier 6 жыл бұрын
Thanks Roger. When I started out with Lime stuff in 1995 (ish) we mostly used St Astier NHL 3.5. I thought the whole subject was a load of tosh but it works and there is a saying that the slower it takes to dry, the better it sets. The quicker something takes to dry does not necessarily mean it's stronger, cement relies on compression strength for it's set and a structure like the Hoover Dam is an amazing build and worth watching how they did it. Strangely, cement can continue to strengthen up to 6 years later and adding fibres to lime or cement really does increase the tensile strength, almost doubling in some cases. They sell a lot of NHL's in builders merchants, especially Hansons which works but like many hydraulic limes is too strong, the minimum I'd use now is an NHL 2.0 (Natural Hydraulic Lime) but as I said, a putty is better and if you slake your own quicklime it doubles the quantity and is fantasticly explosive and gets super hot. So doing a feature on 'hot lime mixes' would be a good one to do. The builders of old would have dug a pit on every site and slaked their own lime which is why you see bit's of charcoal in old pointing and mortars. The masons like hot mixes because the stuff expanded in the joints and it mean't bringing less putty to the site. Could you perhaps also do a film about the rising damp myth. Too many people are being ripped off having work done like damp proof injections, this is an ineffective and pointless cost, these contractors really talk bollox and should be charged with fraud I think. All the best.
@Zulu415 5 жыл бұрын
You don’t put lime in your first coat, 2nd coat will dry too fast. 4:1 sand and cement first coat. 4:1:1 for second coat for me 👍
@rogermoore7069 5 жыл бұрын
same as that no lime first coat 4 and 1 finish 4 1 1
@iekuieku1536 Жыл бұрын
In fact lime will set, its called carbonation and thats how limestone was made in the first place. lime needs a fair amount of time to set though, approx. 1 year per 1cm of depth. in the early years people plastered only with lime and no cement, im doing that as well, you just have to be careful with the render in the beginning to not scratch it.
@nigellilburn4323 4 жыл бұрын
Great detail, superbly presented. Thanks
@jdc9128 6 жыл бұрын
6-1 seems awfully weak for scratch coat , 5-1 or 4-1 on scratch then 6-1 on top coat for me ! And I don't know a single plasterer that has the time to let the mix sit for 5 to 10 minutes before laying on , I'm laying it on as the labourer is loading the spot board it's gone by the time he gets back to the mixer then I'm screaming at him to hurry up
@SkillBuilder 6 жыл бұрын
I am glad I am not your labourer. Charge more and relax
@jdc9128 6 жыл бұрын
+Skill Builder unfortunately that's not how it works in the area I live in , charge more and you will find yourself sitting on the couch 7 days a week , working through tennis elbow and aching shoulder has become the norm , but I wouldn't change it for the world , plastering is a hard game , drive on !!
@SkillBuilder 6 жыл бұрын
Yeah I know and it was disingenuous of me to suggest that but it upsets me that building workers are driven like dogs while people sit back and make millions out of property. The industry demands that everything is done, faster and cheaper and the reason is so people who, have probably never done a day's graft in their lives can make more. It isn't that far removed from slavery
@jdc9128 6 жыл бұрын
+Skill Builder very true !
@stevebentman1139 6 жыл бұрын
U Da Man Roger!
@chizzlemo3094 Жыл бұрын
thanks mate! Top tips before my DIY disaster
@barrybloggs22 3 ай бұрын
Great videos Roger, what’s your opinion on the breathability of cement renders ? do you think the lime helps ?
@SkillBuilder 3 ай бұрын
kzfaq.info/get/bejne/sMmAp8aH38_NoaM.html
@barrybloggs22 3 ай бұрын
Thanks Roger, that’s awesome, keep up the good work
@asterixborden-koi6881 3 жыл бұрын
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 👍
@chrishodges1672 6 жыл бұрын
Just seen a few of these video's. Excellent. I mean, really excellent.
@richardbaron2948 2 жыл бұрын
Just what Ive been looking for!!
@zaharina82 2 жыл бұрын
6 parts sand, 1 cement and a bit of the soapy liquid. Got it. Thanks.
@buttheadpink 5 жыл бұрын
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.
@db7610 4 жыл бұрын
Great tip about lime in render, I specify and see so many 1:3 as standard, in books too! Stay safe guv
@ellamarkey1329 3 жыл бұрын
Hegrewt
@hkinniable 3 жыл бұрын
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?
@dooovde 2 жыл бұрын
no
@davidrennicks2484 Жыл бұрын
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.
@SkillBuilder Жыл бұрын
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
@kelvindawe5123 2 жыл бұрын
Very helpful Roger thanks.
@srlfc90 Жыл бұрын
Can you do a video on Brick Slips Pros and Con of it. To be used on the external of the building
@MrRline1 3 жыл бұрын
Why not put lime in the scratch coat as well?
@SkillBuilder 3 жыл бұрын
Yes good idea
@terry4144 5 жыл бұрын
6 : 1: 1 = 3 sand Cement+3 sand lime which is actually a strong mix
@catmonkey6826 5 жыл бұрын
I think the strength issue is with the proportion of sand to cement. I do 5 to 1 with a shovel of lime added to the barrel.
@agee8322 11 ай бұрын
Hydrated lime DOES set. Used it at 1:2 with sharp sand for flintwork. Still good 2 decades later. Also used it for render and plaster.
@SkillBuilder 11 ай бұрын
I am not a scientist but I think what you have there is a natural pozzolan in the sand. The addition of pozzolan to any lime mortar (hydraulic or non-hydraulic) will modify its characteristics. Pozzolanic materials can combine with uncarbonated lime (calcium hydroxide) to form stable compounds, thus reducing the risk of early leaching or frost damage and increasing the potential durability of the mortar.
@agee8322 11 ай бұрын
I did an experiment years ago - made a filler out of normal hydrate (not NHL) and water - carbonated (set) hard. Sand from my pit has no clay content, so no pozzalanic inclusion. A lime company around here were trying to say that all lime historically was NHL - which it wasnt as it was all from burnt chalk - so not NHL. But, inclusion in aggregates and ash from lime kiln would have a pozzalnic effect, but not even as much as an NHL 2 from clay rich limestone. Try a 1:2 hydrate and sand mortar - 2 days and its very much done on initial set ..... carbonation much longer thereafter. Even Historic England are ok with the use of hydrate now (although they say 1:3, not realising that this was historic mix of quicklime and aggregate - once quicklime slakes, it can double in proportion, hence l use a 1:2) But, in essence, no pozzolan needed for a normal hydrated bag lime.
@ujalabalakrishnan4295 4 жыл бұрын
Very useful information...simple and comprehensive..
@richardsandwell2285 7 ай бұрын
Its strange really, I think it is a black art, I admire builders, I have no fear of electrics, gaswork, or any plumbing , but plastering and rendering scares me to death . One success I did have was on a waterfall for a pond, it comprised of sandstone rocks and mortar between , it leaked badly and needed a solution, rightly or wrongly my dad and myself mixed up a very strong mix that would have you builders shouting at us. It was 2 parts Sharp sand and 1 part portland cement, we had cleaned of the rocks with a wirebrush and added a layer of galvanized chicken wire to the waterfall run . We did it all in one go and did not stop for breaks , I will probably regret saying this and jinks things but that was 32 years ago and no cracks or leaks, we did at the time paint it with a non toxic fish safe bitumen emulsion, but most of that has long since eroded away. But I do understand the theory of using weaker coating normally on the outside.
@thamesbuildingsupplies1984 Жыл бұрын
brillant video mate.
@djyul 5 жыл бұрын
At last a video that tells straight away what and why and how much. Brilliant! Given your body some blood as well 😉
@johnpearman7283 4 жыл бұрын
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
@SkillBuilder 4 жыл бұрын
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.
@darringodden7225 Жыл бұрын
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?
@dionweston9712 6 жыл бұрын
I add one good turd to a mix and the plasticity it gives the mix is second to none, especially if you've had a cheese evening the night before.
@dannysmith2040 6 жыл бұрын
Dion Weston I use piss and poo 2-1 ratio ,takes a while to cover the wall but the finish is unbelievable!
@dannysmith2040 6 жыл бұрын
F 8 and piss .
@madeinuk68 5 жыл бұрын
Add to that one level tablespoon of monkey spunk,and you will find you will get a lovely even consistency.
@aliceallen4604 5 жыл бұрын
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
@SkillBuilder 4 жыл бұрын
Sorry Alice. I have only just come across this comment. PVA should never be used outside. SBR is way better.
@philipm1896 2 жыл бұрын
@@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.
@iaintait772 Жыл бұрын
@@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
@philipm1896 Жыл бұрын
@@iaintait772 building houses 35 years not one has fallen off, guess you are wrong.
@iaintait772 Жыл бұрын
@@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.
@matthewcunningham2399 4 жыл бұрын
Well done Roger, great tutorial. Cheers
@chriscargle7645 3 жыл бұрын
Great vid👍🏽
@michaelfallon2280 4 жыл бұрын
Great video. Really informative for the DIY'er like myself.
@abscomm 6 жыл бұрын
Love it! I've always had problems keeping the muck on the wall, maybe, finally, I'll be able to do it right.
@scottleft3672 4 жыл бұрын
Start small.
@whoisme678 6 жыл бұрын
4:1 I've use and its still sticking after 30 yrs
@FirstLast-fr4hb 6 жыл бұрын
How often have you checked up on previously completed projects, and after what periods of times? I think its a good learning habbit of all those details people tend to overlook when it comes to things that effect down the road.
@criartoros 4 жыл бұрын
Is that 4 sand 1 cement?
@SkillBuilder 4 жыл бұрын
@@criartoros yes that is what the man said. The problem is that on a weak substrate that is a strong mix and it will crack. Put one more sand in and some lime and you have a lovely mix.
@trimad6128 4 жыл бұрын
Always used 5-1 on render and weaker on stonework.also I prefer more of holm sand mix as it floats up really nice.
@paolenchungkilong1558 3 жыл бұрын
your talking tomuch
@anthonyskilton8634 3 жыл бұрын
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)
@SkillBuilder 3 жыл бұрын
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.
@anthonyskilton8634 3 жыл бұрын
@@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 ?
@andrewhelmer7710 8 ай бұрын
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?
@gdfggggg 5 жыл бұрын
So are you saying sand, cement and plasticiser for scratch and sand cement and lime (no plasticiser) for top coat? Cheers
@crazygeorgelincoln 5 жыл бұрын
Never spotted lime in Wickes, not that I was ever looking for it.
@tamburlaineman 5 жыл бұрын
crazygeorgelincoln they sell em in Tescos next to the lemons
@shaunsart 4 жыл бұрын
You rendering is like Rory McIlroy showing us how to play rugby
@samat2701 6 ай бұрын
Hi You said 6/1/1 I understand 6 renders sand How much is 1 part cement Or 1 part lime Should I one bag cement divide to 3 parts
@nobreighner 3 жыл бұрын
Excellent explanations!
@mariusm5187 3 жыл бұрын
Great video really helped me out!!!
@MarkAndreYapching 3 жыл бұрын
Thank you sir, a very big help for me.
@royb2251 Жыл бұрын
Roger’s the man 👍🏻
@teachweb69 2 жыл бұрын
I love your channel Roger thanks so much
@teachweb69 2 жыл бұрын
As I have retrain to become a plumber late in life I've just gained so much from your channel particularly
@georgianwindow 3 жыл бұрын
Thanks That's the information I needed
@gonefishing8947 8 ай бұрын
Will this be a breathable enough mix we have installed plaster insulation internally on our old property so need the breathability and this looks easier than using lime render and no cement
@EddieHickman-cc7nt 4 ай бұрын
brilliant video
@alanyoung7532 Жыл бұрын
Really useful practical demonstration on external rendering and the dangers of using an overly strong material. Further technical guidance on rendering can be found Building Research Establishment publication “Good Building Guide No 18” (Choosing external rendering) as this provides authourative information, including clarifying suitable preparation options, appropriate mixes for different backgrounds and exposure levels, and examples of good detailing. It might be also be worth bearing in mind that strong mixes (and plastic paints) inhibit evaporative drying and can trap moisture.
@TheMahoney65 Жыл бұрын
Thank you Roger
@Chain21SAW 3 жыл бұрын
Nice one .. is that Daniel Radcliffe on the mixer ??
@margaretcronin4073 6 жыл бұрын
Nice video mate very explanatory.
@just-dontbs 8 ай бұрын
Great video.
@appleidid9055 Жыл бұрын
A brand new trowel says it all
@SkillBuilder Жыл бұрын
Yes it is hard to hide. The trouble is that all the major trowel manufacturers keep sending us trowels so we use them once and give them to our plasterer friends.
@DeeJay003 6 жыл бұрын
What a great tutorial. Nice one.
@Salverstein Жыл бұрын
2023: "Scientists discover self repair capacity in ancient roman caementum"😃
@nige1568 5 жыл бұрын
I've been a good general builder and stonemason for over 25 years. I've seen labourers with better trowel skills than this guy. Far too stiff too. I'd throw this bull muck back into the mixer. What's he on about "don't use building sand"??? A good 4 to 1 building sand to cement with a dash of elasterciser, waterproofer or even fairy liquid (if none of the first two). I get fed up with these DIY videos!
@SkillBuilder 5 жыл бұрын
Nige Where in the title did it talk about learning trowel skills? I am talking to the camera about the best mix and yes it has been hanging around for a while. All plasterers will advise against building sand, it contains silt and clay and is not washed. It will shrink and crack. That is why they sell plastering sand. As soon as you mention Fairy Liquid you show that in your 25 years you have learned very little. It is not elastericiser, by the way, it is plasticiser.
@nige1568 5 жыл бұрын
@@SkillBuilder Hi Roger Apologies mate I've been watching all your videos. Ive watched all your 'how to build an extension' ones and I can see you're are very knowledgeable. As a builder of many extensions myself (and doing all my own labouring for many years...... suffering a bit now though). I can see that all your work is of a very high standard.....quite old school with modern thinking if you know what I mean. I liked how you built the engineered brick pier to take the weight of the steels instead of laying them on the lightweight Newton blocks. Good building practice. Also liked how you explained all the complexities of ridge and wallplate level and made it sound simple for laymen and novice builders. The 3:4:5 measuring took me back to my apprentice days. Brilliant and never let me down. Much more accurate than my big bendy square. Liked all your drainage videos too. Very good. All very neat and tidy. I once had the same problem with concreting a footing whereby they couldn't get access to the back end of my extension but the company insisted that the concrete will easily flow to the other end! Huh. I was raking it back for about an hour. For future jobs like this I then insisted on really runny concrete because one of my old building inspectors said that it didn't matter how wet concrete is. Anyway sorry for 'rabbiting on' I've subscribed to your channel and will recommend it for any budding young DIY ers or professional construction workers!
@freshpootube 5 жыл бұрын
Rob Songer expains why dish-washing liquid is bad idea to put in your mix.
@callumari3199 5 жыл бұрын
So many different opinions on the mix ratio. i am now confused and i want to render a low limestone garden bed
@conorcoyle6763 4 жыл бұрын
How do you measure the amount of sand you need to buy? What's the coverage?
@stevecrowable 3 жыл бұрын
Hi Great advise, does it apply to a chimney stack with a liner fitted. Thanks Sreve
@SkillBuilder 3 жыл бұрын
Yes it does but if it is exposed you may want a slightly stronger mix or some mesh reinforcement to stop it cracking.
@sarahbeverley2109 Жыл бұрын
Can you have lime in the scratch coat (sand, cement and lime) and if so what ratio for the scratch coat and what ratio for the top coat please?
@sundayfooty 3 жыл бұрын
6:1:1 still a good mix for old red brick walls that need rendering?
@lacihalasz Жыл бұрын
You put 1 coat... Is that enough? Here we can buy a render for outside for first rough coat and then 2.coat fine coat..
@edmtb1603 4 жыл бұрын
Very helpful, thanks!
@seanmoran1056 4 жыл бұрын
Good video , should the Windows not be in before you render ? Or can they go in after ?
@SkillBuilder 4 жыл бұрын
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.
@samketteringham6070 2 жыл бұрын
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😉
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