Aircrete Blocks Cracking up - Unwanted Trouble
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- čas přidán 9. 05. 2021
- Why do aircrete blocks crack up so often? As with so many of these problems, everyone involved is pointing a finger at someone else. Is it the blocks, the brickies, the plasterers or the architect who is to blame?
Aircrete blocks are lightweight and have a very high degree of insulation. When introduced, they seemed like the wonder product of the age and to some extent, they do a job that no other materials can do.
I think it’s accurate to say that when they were first developed the intention was to use them on internal skins of cavity walls instead of breeze blocks which are heavier and not such good insulators.
This is still where they are mostly used. There are however a growing number of buildings being built with external skins of Aircrete and there are even buildings being built with solid Aircrete. That is to say no cavity.
The appeal of Aircrete blocks over bricks is speed and cheapness. They are a good product in their way but the builder needs to understand their limitations.
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#Aircrete #buildingmaterials #construction
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This is so interesting, expecially in light of the widespread aircrete issue recently announced in 100s of UK schools and municipal buildings.
More to come on that subject is a couple of days time
There's a couple of differences in the naming, but these blocks look to avoid the worst risks of the RAAC story in Britain. What I know of that scares me is the long panels and beams. These blockwork walls are under compression loads. The RAAC beams and panels, supported at the ends, get a tension load at the lower side.
The descriptions I have seen include other problems, associated with the reinforcement, which I don't see any sign of here. But this video showed a couple of details that could be easily missed - the strength of the mortar and the expansion joints.
The RAAC failure mode seems nasty - less warning time than we were promised for an ICBM attack.
@@davebell4917 just on the face of it, anything-crete under tension is simply bad engineering, end of.
That is an RAAC issue, not aircrete. Different stuff used very differently
As a fifty five year old bricklayer this lack of basic knowledge drives me nuts.
We used to have Clerk of the Works on sites monitoring the standard of work and materials used.
They got rid of them and the problems like cracking started.
Instead of asking the tradesmen what was happening the college boys thought they knew best and started coming up with all these solutions, expansion joints, stainless steel rail tracks etc. These new ideas actually weaken the wall in a secondary way.
Roger was correct when he said, you shouldn't use a mortar stronger than the material you are using.
Any building older than a hundred years ago had no cement whatsoever, it was all lime sand mortar with no cracking problems.
Most modern problems are the engineers being obsessed with strength, "Strength is better so make the mortar stronger." No, that is the cause of most of the problems.
Go look at a terrace row of Victorian houses, nine inch solid walls a street long, not a single crack from one end of the street to the other.
Go look at huge Georgian houses, no cracks.
Go look at huge Roman buildings that have stood for two thousand years, no cracks.
But of course, we need to make our mortar stronger and add reinforcement to it.
Is it me?
Couldn't agree more. Top comment
@@FlamesOfThought Thanks Jack. We just know
Was a subby 40yrs. You're spot on.
I would add that every sand has different characteristics when mixed. And a simplistic specified formulation of 5:1 or 6:1 etc always catches the college learnt guys out.
It's practical application that determines a mix.
@@thertis580 I agree, gone are the days when you could walk into a builders merchant and ask them what soft sand they have. Now theY say, it's just builders sand.
How I long for a bag of Runfold or Westerham. (The local sand quarries when I was a lad)
@@harveysmith100 dont forget to add,every render coat,is weaker than the last one applied. As you head to the finish coat
I love these “Skill Builder” videos, and the way that Roger explains things is a breath of fresh air and easily understood.
Something about the old pom builders thats just so straighforward, no knocking around - Pure and simple.
Not like those americans blah blah bah
A skilled tradesman is invaluable. I'm always amazed at how many details go into a trade like masonry or carpentry. Great video!
This was eye-opening and helpful. I never thought about the consequences of mortar being too strong.
Spot on Roger, doing exactly that on my extension, doing it all myself as didn't trust any brickies at work (I'm a carpenter)
Only one guy ever used lime before ,when he was an apprentice, they don't seem to learn much, as a proper bricklayer is a skilled and comprehensive trade when you get into it, but as most trades nowadays it's watered down to a basic craft for speed etc needed to get that off the chest, cheers
Same here - building my extension for that very reason. Asked the mortar question yesterday to a bricky in screwfix who replied they use exact same mortar on both skins, concretes and aircrete.
Lime is the way forward
Sorry richard for your experience but I do agree, the need for so called tradesmen/bricklayers was so high they invented an NVQ. worst thing that ever happened to my industry. passing people within 6 weeks for a job that took at least 3 years to learn with intensive training . Blokes that I learnt from were on a 7 year apprenticeship
@@scottnever8732 There are too many things that only come up now and again to be taught in 6 weeks. People also do not remember everything they are taught first time. You get decent craftsmen if they do a year in the classroom then a couple day release. then they get to be on different sites and see different things and problems.
@@scottnever8732 NVQ?
Not Very Qualified...
Didn't he do well kids?! Only the slightest glint in the eye when the background noise started 😂😂😂
Great little video though, informative as ever.
Way impressed what a total clear and concise video with everthing gone through and fully explained 👍🤘
Yhea, I am absolutly allergic to wet trades and ground works. So it's a nice head up on stuff I don't/won't get involved in. I can't knock this lot to be fair. Sometimes there is a a bit of a fuck up, but you have to piss with what you got at the end of the day.
Bollocks, he says the weight of a JCB and he'll have meant an RSJ. Re cracks he's saying the cracks will be in the mortar if the mortar mix is 'right'. How is that better? And Nm (Newtonmeter) is not a unit of pressure, and 3.5 Newtons is like 4 apples of weight so that can't be right either. He mentions reinforcing mesh in the mortar; he should have said the first coat of plaster. The aerated blocks in my extension are riddled with cracks..bottom line ..aerated blocks are a crap building product.
@@hectorheath9742 The problem is you think you know, but have no idea.
@@UberAlphaSirus Oh really, Sirus? You've gotta defend your comment with a reason or reasons. Tell me what's wrong with my accurate review of this shabby vid. But you'd better read the rest of the comments first.
@@hectorheath9742 I told you already. "The problem is you think you know, but have no idea." I read everything you and others said before. What do you want me to do? I can't un thick you.
I'm not a bricklayer but I am a qualified engineer so when I built my own home I read up on this in detail and consulted my inspector. We decided upon using a 5/1/1 mix for the mortar one was lime. We also looked at where to put an expansion joint in a 12m front wall facing the sun. There were four windows in the ground and first floor ( Brick faced and 7n 140 mm light concrete block internal) in the 22 years there has been no cracks inside or out. We did fit bison Hollow core planks 8m single span that also helps to prevent movement of the inner leaf by absorbing the heat and cold expansion/contraction with underfloor heating to maintain a consistent temperature level., also we kept the windows on both levels 1.2 m from the corners to avoid stresses there Hope this helps.
Dad made the brickie use lime in the mortar with our first house that we built back in 87. None of the brickwork has cracked even though other parts of the house had moved. I don't know what the ratio was but it has lasted.
Very interesting. Many years ago as a teenager, I mixed mortar for my old man when he was laying block. That built up my muscles fast. We used lime in the mortar. I became an Army Combat Engineer and a Civil Engineer. I avoided using bricks and blocks because I found that there was too much inconsistency with our masonary work in my area. Very good video. Good Luck, Rick
The mortar doesn’t hold the blocks together, it holds them apart. Grin.
could something not do both? double grin.
[grin] I like the use of plain English emojis. [wink+thumbs-up]
Say what..
He's right, you know. Most masonry is very strong in compression, but useless in tension. That is why a shifting foundation always yields cracks, and never smushes the grout out of the joints, and you never see bricks crushed.
that's why they used lime it accommodates for movement lime is a softer mix that cement
So so so refreshing to listen to someone who has knowledge from experience and not someone talking about what they did last Tuesday for ten minutes and two minutes on what you clicked on, based on what they think from watching someone else doing it on CZcams
Job well done and a job done well!!!
OUTSTANDING explanations. It pays to attend to these details if you want a lower maintenance home. Super helpful info.
Movement joints for blockwork are approx 6m in any straight run and 3m from a corner. This can extend to around 9 and 4.5m if you use bed joint reinforcement. It's closer to the corner as it's a point of high restraint. I say "approx" as if you were to
put a joint after say 7m it won't definitely crack it will just have a higher chance of cracking.
Roger, you hit the nail on the head with the mortar.
I love how the way he demonstrates it moving “in and out” at 1:34
It’s like you knew about the potential RAAC issues before they were made public knowledge. It’s a pity that those in power and authority do not consult skilled and experiences engineers such as yourself. Love your channel, as an electrical engineer, I still find it fascinating and your delivery of information is on point. Absolute professional and fantastic educator. Wish you all the success with the channel
This is aircrete, the bubbles come from aiding aluminium powder. RAAC is made in an autoclave and has reinforcing (giant pressure cooker) It stands for Reinforced autoclaved aerated concrete
Regarding the mortar not being stronger than the brick. This now makes sense why the 'hebel' blocks produced in Australia have their own specific mortar. Very good to know and thanks for the video
Amazing - the quality of these tips and advice can put many a college to shame. Good job
Here I am watching a British man talking about mortar and air Crete with no general usage for this information aside from personal knowledge. Great presentation and now I can maintain a conversation about the subject with my mates that are in construction.
Feel like I am repeating the praise levelled at Roger from the many comments below but without the effort Roger puts into these videos the world is a poorer place. 'What we do in life echos in eternity' -
Thank you Ivor.
Fascinating! Would never have thought you can have too strong a mortar but hey you live and learn, thanks Roger! Good job I'm not a builder ha! Really clear and well presented video, top class production.
Precise, well worded, simply explained and no unnecessary drible.
Thank you and I hope you are alright and in good health Rodger - you're a treasure in the trade
Very useful tips. I especially liked the tips about the different mortar mixes for block and brick. I never knew that! Of course, I’m no concrete or brick laying expert. Thanks!
I liked the presenter right off, he just sounds and looks like a journeyman, expert builder.
I only saw this on a new (ish) build,googled it - found the video, result = explanation / relief.. Nice 1 Roger 😅
Great video - I learnt a lot there. Thanks Roger! 👍🏻
Many thanks for such a clear explanation. I now understand why the block walls inside my internal garage have cracks in them. The house is around 25 years old with dot and dab hiding most problems but not in my garage.
Such a legend Rog!
This fella is outstanding.
My house was built by Redrow in 1997. Lots of these celcon lightweight blocks visible in the loft, a lot of them cracked and I noticed whilst being built that the upstairs floor joists are are laid on these blocks where I would have put a wooden flat bearer to spread the weight. I have also noticed that the celcon blocks have also been used underground in the main foundations.
Roger, well done. Straight to the point with the facts. 👍
Great advice Roger!
Great video! Fascinating and very knowledgeable, Roger! Thank You!
another excellent video, ive been told to keep the block dry as well , thanks for sharing your knowledge.
Yes it helps to keep them dry but that is not always easy to do.
Bloody brilliant 👌🏼🏴👍🏼
Great job once again, thank you.
Thanks, Roger, that opened my thick head up. You have saved me a lot of bother. Good man!
I've noticed here in the states that building construction has taken a turn for the worse, materials are sub-standard, workmanship is atrocious and a general lack of pride in what's been constructed. Back in the day we had trade school education in regular high school, now all that is gone. I don't know if you see this where you are or that maybe it's a touchy subject to comment on!
The more houses fall down, the more new ones you get paid to build.
It's common sense to me when you see castles from the 1500's still standing and luxury apartments from the 80's collapsing and killing people.
If we still built our buildings like they did in the dark ages, they would all still be here and most builders would be out of a job.
@@colmreynolds9869 Take a look at the heating bill of a castle and you will wish the ceiling had collapsed on your head instead.
Another interesting video, you explain these things really well.
Thank you very much!
That’s why we use either glue or mortar of 1mm in Europe, both for cracking and to not loose the insulation properties
I have used thin joint adhesive and still have cracks. I think it is due to the moisture in the blocks. They shrink as they dry and the glue holds them too tight. Answer dry blocks
aircrete was design as filler material for partition/non weigh bearing walls. supposed to be put inside rigid cadre that takes the load- key word rigid. So steel/wood frame = no go. Should go under concrete frame-post and beam, even that will give you crack at joints, so best option drywall/mesh-fiber glass of chicken wire over.
Excellent advice. Thanks for sharing
Your work's so neat. Thank you for this.
i was told many years ago by a long retired foreman who went to see Celcon blocks being made ( from one massive block and the wavy lines in the blocks are the marks of the saw teeth that have cut them up) that the manufacturers specified laying 100mm expanded metal lath into every third horizontal course . Goes to say that ive never seen it done.
That is true
Lovely Malcolm McDowell “A Clockwork Orange” tribute at 1:35 complete with in-out hand gesture and authentic accent.
And I thought this was about laughing blocks - still, enjoyed it and subbed. Thanks!
This is excellent - very thorough!
Really appreciate this video! Question: What are your thoughts regarding AAC blocks that are interlocking? And, the mortarless stacking of blocks (expect for first run of blocks on slab or cmu block stem walls) in which closed cell foam is applied instead?
Wow! Excellent presentation and superb information. Thank you!
Excellent advice Roger !
Really enjoyed the video, don't know anything about brick laying. I just replaced the vinyl on my house, and had to follow the same rule about allowing movement, in my case to prevent buckling and distortion.
Those aircrete always make me nervous, they’ve got the consistency of a wotsit
A wotsit? I dont know what is it?
AKA a "What's it"
@Bercilak de hautdesert a puffy air-filled one
Wotsit! What a Whopping Whoosh!
Hmmm.... ? Looks like that's a trade of personality BEING NERVOUS. Just do something even if its wrong
Great video Roger!
Roger Bisby & Common Sense ..... Always in the same room together :-)
Brilliant channel. Full of useful information
Much appreciated!
Very interesting. I was always worried about these blocks in my old house - drilling into them was like drilling into fresh air and they generally seemed extremely weak.
Awesome explainations, thank you.
Excellent mate spot on 👍🏴cheers
We've all known about the mortar being to strong for years but nothing changes especially on new build with silo muck, same old story quantity over qaulity
Agree silo muck is used for concrete/thermo lite/ and the many different bricks used on site. Whether there engineering brick or soft stocks. That’s why these new houses have massive shrinkage cracks when the thrown up in the depths of winter.
Very well explained - you should lecture Specification writers and Building Designers - best explanation I have heard in 30 years Cheers keep up the good work.
Thanks Roger for great video, loads explained. Have seen new builds (not particularly big) where expansion joint hidden behind drain pipes at corners. That alarmed me that the gable then does not appear restrained properly (unless there are some hidden straps or clever ties). Suppose the roof timbers though might have more restraint straps and perhaps the floors also to keep it all together.
Best teacher in the world.
This guy really cracks me up! 😂
The problem is typically inherent with a wrong strength mix! The mortar joints need to be at least 10% less strength than the material being laid,
Hi Roger, it's the same here in France. Sadly you often see stone walls repaired or repainted with cement instead of lime mortar. Trouble ahead I am sure. Mike
Great clear explanations .
Thank you for for aharing these tips!!!
Thanks, Harvey. This was SO incredibly helpful. I have watched hundreds of aircrete evangelist videos, and none have addressed this. QUESTION: Does using something like basalt fiber in the concrete with which the bricks are made abate this problem as well?
thx for sharing your years of practical experience, detailing what to do to help prevent Aircrete Block cracks.... and a few good tips for working with any cementitious block...
But your main point is hire trades people who have a pride in their work, and will not cut corners.... Since knowing what to do vs doing it are 2 different matters... But even then you need other people such as the general contractor or ourselves spot checking its done to specs.. Check it 2x (or 100x) times and cut once is good general rule....
Excellent video, great information.
Used thin joint on my extension and used reinforcement every couple of layers. Used monocouche rendering on the outside on the blockwork. Much better, and a better finish.
Brilliant info 👌 thanks
Excellent video, thanks
I also thought lightweight concrete was a great way to save time, mortaring blocks of them vs pouring a tilt-up wall seems backwards! Anyway great video, concise no nonsense
Smashing video did not realise how important mixes were when dealing with different tasks, I amgoing your and build a small seating area which will be inside a breeze block walled area, and hopefully render so this video has been sooooo helpful thank you
Thank you for educating the uninformed, enjoy learning about this topic.
In warm conditions these blocks absorb the moisture out of the mortar as it is spread .Always soak the blocks when laying .Bigger cavity and clinker blocks preferred choice .
I'm laying my first blocks & they soak out the mortar moisture wicked fast in 32 C (90 F) temps. But my block mfr does *not* recommend pre-soaking. So, 2 questions...
Are you talking about aerated or autoclaved aerated (or both) and what is your pre-soak rexommendation based on?
Brilliant video.
Cracking bit of advice there Roger!
Bed reinforcement (such as by BRC) is available, laid typically in alternate the bed joints to allow the movement joints to be spaced further apart or even omitted.
I could not agree more with that video. well explained
In Central Europe most interior plastering and exterior rendering uses fibreglass mesh embedded in a flexible adhesive, then topped with a flexible silicon render. It leaves a more textured finish than finishing plaster, but is less prone to cracking.
Thank you for this.
Very helpful, thank you!
I know nothing about all that, yet i still understood most of it.
I was expecting a video about why aircrete is bad, but this is much better.
Excellent presentation!
Thank you kindly!
Everything he said was bang on 👌
Great informative video
Lol this is now a scandal 2 years after you posted this. Nobody listens!
No... You're talking about RAAC this is a different material
Bravisimo Maestro 👏🏼👏🏼👏🏼
6:1 mortar and EML every second course everywhere.
I have used this method for the last twenty years and it works.
I pay £6 for a 20m roll of EML, this covers approx 18m2 blockwork, works out at 33p per m2.
It's a no brainer to me.
As you said Roger the brickies don't like the tramline reinforcement but the EML is easier to use.
What is EML?
Do you use stainless?
Expanded metal lath.
totally impressed by your tech knowledge! wow! I am thinking now of using fiberglass more. however I will keep your video filed for reference and try to follow caution as much as possible.
Excellent video. Sounds like a ‘wonder block’ which creates more problems than it solves. I drive past the 100+ year old terraces and wonder how far we have come. Fast fashion, fast food, fast houses?
We use Ytong a lot where i live. With that stuff you afe supposed to use their recommended mortar and no more than 3mm thick. That looks like a ton more mortar there than they use here
Thanks Roger, sound advise thanks.
Lime spread here, I don't like to see expansion joints or use angle-bead on corners but I can see why they are necessary.
At the start of the pandemic I built a 7 meter, half-round, rubble stone & old brick lime putty mortar wall without a concrete base and no expansion joints about 4 foot high, 3 stones wide with a stone & mortar infill to hold the end of my veg garden in.
Finished in 3 days (lots of big stones) and about a year later big cracks suddenly appeared right from top to the bottom in 3 or 4 places almost where the expansion joints would have been.
From the end of the wall to the first crack was about 2m.
Interesting stuff, thank you!
I wouldn't buy a new build older houses are solid
I always like knowing if it stood for 25 years and still looks good the problem you will fined are usually just cosmetics.
Are yall writing with an English accent? I'm reading and it sounds like an English accent.
Agree, unfortunately old homes are going to get penalised soon, checkout the new Future Homes Standard.
Leaded pipes, asbestos, aluminum wiring, roots in septic...But the wood is tight grained! :-)
@@TheRainHarvester aluminum wiring was an experiment in new home construction 20 or 30 years ago. it was short lived as the resistance caused the wires to heat up and burn the house down.
Very informative video
Top video! 👍