The Ugly Truth About Reinforced Aerated Autoclaved Concrete (RAAC)
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- Опубликовано: 3 окт 2024
- Read Roger's article on Reinforced Aerated Autoclaved Concrete (RAAC).
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RESOURCES
Information on Reinforced Autoclaved Aerated Concrete (RAAC)
🔗 shorturl.at/adoHZ
GOV.UK RAAC Identification Guidance
🔗 shorturl.at/uHT28
Structural safety of reinforced autoclaved aerated concrete planks
🔗 shorturl.at/rFQT2
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ABOUT RAAC
Reinforced Aerated Autoclaved Concrete (RAAC) is a specific category within the family of lightweight concrete materials. Let's break down the components of its name to better understand its properties:
Reinforced: Like many concrete types, RAAC can be reinforced with steel bars or mesh to increase its tensile strength and structural capabilities. This reinforcement allows the concrete to withstand forces and stresses that it couldn't bear on its own.
Aerated: Aerated concrete contains many small air pockets or bubbles, which are introduced during the manufacturing process. These air pockets make the material much lighter than traditional concrete and provide it with good insulating properties. The air pockets are created by adding a foaming agent to the concrete mixture or by a chemical reaction between certain ingredients.
Autoclaved: Autoclaving is a process in which the concrete is subjected to high pressure and temperature inside an autoclave (a type of large industrial pressure cooker). This process accelerates the hardening of the concrete and enhances its strength and durability. Autoclaving also results in a more consistent material with fewer defects.
The advantages of RAAC include:
Lightweight: Because of the air pockets, RAAC has a lower density than traditional concrete, which can lead to savings in transportation and construction.
Insulating properties: The air pockets in RAAC provide it with good thermal insulation, making it suitable for use in energy-efficient building designs.
Speed of construction: RAAC panels and blocks can be manufactured in large sizes, allowing for rapid assembly on site.
However, RAAC also has some limitations:
Lower strength: Even though it's reinforced, RAAC generally has a lower compressive strength compared to regular concrete. This means that it may not be suitable for certain structural applications.
Sensitivity to moisture: RAAC can be susceptible to moisture penetration, reducing its lifespan if not properly managed or protected.
Despite its advantages, RAAC has seen a decline in popularity in some parts of the world due to concerns about its long-term durability and incidents where failures occurred. If considering its use, it's important to consult with professionals familiar with its properties and potential limitations.
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#concrete #construction #reinforcedconcrete
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I’m a Chartered Engineer and it worries me how pretty much everything is built for the lowest possible cost. Not just buildings, but also cars, machines, electronics.
It’s a great explanation and it is the ugly truth.
£18.5 billion to refurb the Houses of Parliament, £370 million already spent on the refurbishment of Buckingham Palace. Oh, and however much Ukraine wants on top.
I’d argue if you’re a chartered engineer, then you have the responsibility to ensure specifications is met, along with the ER’s and to ensure you don’t value engineer it based on bottom line. Too often I’ve seen consultants buckle on their own specification and allow a project to go from spec driven quality to contractor led d&b. In short, consultants and contractors are both as bad as eachother.
I'd argue that cars are just ridiculously over complex.
The accountants rule. I work for an Italian company and they are opposite. They built us a new factory with underfloor heating, automatic windows. Granite tiles in the toilets, automatic doors, taps, toilet flush is even automatic.
As a Chartered engineer I know there are building regulations and design standards for everything from silicon chips to cars and trains. This means that the cheapest should meet the minimum standards and be safe. I also know that sometimes buildings are built substandard and that supplied materials are either substandard or are found later to be dangerous in one way or another. RAAC and asbestos are two examples. Flammable panels that do not meet UK regulations that were still fitted to high-rise buildings, like Grenfell Tower and Lakanal House, are another.
The worst example is our porous border after Brexit and the likes of Amazon market place letting through substandard food and electronics, rotting meet from Eastern Europe and Asia, and AC-DC mains adapters that short and burn down houses, along with badly-sealed lithium batteries that absorb water and explode, from dodgy factories in China.
After Thatcher’s and the EU’s deregulation drive (cutting red-tape and “better regulation” sound much better than building more dangerous buildings or making more dangerous electronics) we have seen standards erode rapidly over the last 40 years. One example is fire brigades no longer being responsible for checking the fire precautions in buildings. Brexit and post-Brexit trade deals have only made things worse.
Many of these regulations were the results of accidents and medical disasters, from Thalidomide to asbestos, lead in petrol and paint, and now air pollution from burning fossil fuels. We take too long to ban dangerous substances and practices because corporations make large profits from selling and using these materials, and are reluctant to share those profits with consumers and residents who suffered or died from their use.
So it’s a mixture. Standards are good and the cheapest should still follow the standards. But they’re not updated quick enough and the manufacturers of dangerous substances - who often know of the dangers decades before consumers - are not punished hard enough. Regulations are not enforced well enough, and there are not enough investigators to check they’re being followed. Bring back the red-tape I say, and put people before profits.
Having worked for a National builders merchant for over 30 years and attended many courses and manufacturers visits ,also having supplied many of these floor and roof slabs over the years,rightly as you say not just in schools,blocks of flats a good example it is a joy to actually listen to someone who knows what he is talking about on this problem rather than the so called experts on all these media channels and newspapers
Im not an expert, but as an author I did the usual thing and spent 2 days reading the technical and scientific reports. I am amazed by the vast number of internet RAAC experts and people on TV who seem to have read nothing.
The news and media channels only have spokesmen on that speak their narrative.
The curse of the internet , poor information, easy access , lazy ' experts' , and the majority gullible enough to believe what they get from the magic box .
Father was a construction worker at one point in his life, he complained that some of the materials are harmful even with protection and the way they do things is wrong. He was told that he is paid to work and not to think. 5 years later he got lung problems and other medical problems following up, he couldnt do anything anymore got fired.
He suffered for about 15 years, became homeless 3 times, was in prison 2 times and died from lung cancer this year.
I inherited all his remaining debts which were more then half a million euros in total including his funeral and all other expenses and these new bills keep on arriving on my doorstep, if I dont pay I go to prison and lose everything I have just like him and bunch of others, collectively with that move now they want to kill me too with the same flawed systems my father was killed by.
This is a problem in Europe, UK, USA and probably some other places that I don't know of yet and it all came with the USA invasions, before that we never had these problems and people had an actual life before USA and bunch of other fake countries and similar crap even existed.
The typical agenda create a consumer, milk it till it croaks, make things break, milk it with botched works or empty promises, repeat ...
The asbestos thing can't be understated. The RAAC was installed in the 50s-90s when asbestos was a really common material. The only way they've gotten away with keeping the asbestos, which is hugely expensive and time-consuming to remove, is by promising not to disturb it. Which means they haven't been inspecting their RAAC properly. And now do to the inspection, they need to mess with the asbestos, which will itself cause problems even if the RAAC turns out to be fine.
Absolutely right, work in the asbestos industry and a lot of these roof voids are contaminated.
We have started doing a lot of joint visits with RAAC surveyors, we can go up with them and assess any risk from asbestos, we work for a few councils across the UK and they are starting to get very nervous about this, potentially going to be surveying 1000s of buildings in the near future.
It is a joint threat with these collapses, not only the danger of injury due to impact but also exposure to asbestos...
Also heard on the news a concern that teachers who work in buildings with asbestos in them are more likely to get cancer, even though the asbestos is undisturbed.
Speaking of that. The WTC was build in the 70s with lots of it in it. Many of the people working on ground zero after 9/11 wrecked their lungs. It's a bad material... apart from being the best in cheap fire proofing.
Which is why Labour came to the conclusion we needed one plan, to build the entire school estate. Not a drip drop of funding for to rebuild a few schools every now an again. NHS probably need the same approach but with hospitals hitting a billion a apiece that was less feasible.
I would presume the building also contain lots of other materials that would never been use in construction today as well. @@justinclayton3022
An extremely cogent, considered and easily understood explanation of pretty much all of the factors involved in the now suddenly urgent problem across an entire country.
Brilliant presentation sir, thank you.
articulate but his analysis seems all over the place. First it’s water infiltration and corrosion of the rebar, then it’s under spec bearing tolerances, then it’s insufficient or unanchored beam connections and if all 3 happen there is failure. So the material isn’t at fault if it is installed to spec and protected from water intrusion. All of these things BTW can be reasonably retrofitted and water intrusion is basic maintenance. But what’s the goal here? well sensational content to get clicks and monetize the channel. Well done, you had me for a moment. There are far better forensic engineering channels out there to follow.
@@rcpmacI think he is saying that given that any flat roof, under maintained WILL leak at some point. And consequently will damage the RAAC panels. The under sized bearing issues may well be able to cope with the loads imposed, BUT with damaged panels if they start to bend then the panel is much more likely to fail catastrophically and at any time. We're the bearing areas built to proper spec it may well be an inspection would catch damaged panels in the deformation stage before catastrophic collapse. The tying in of rebar at the ends is just yet another possible scenario of a badly built, and not properly certified construction.
Brilliant explanation! If only the politicians could be this pragmatic, maybe the local authorities wouldn’t all be going skint!
If only the maintenance budgets hadn’t been slashed by Westminster, removing the ability for local councils to keep it all in good nick… bloody councils though… 85% of the councils that have a problem with this are the ones that politically were aligned to the austerity programme and did not reallocate funding to maintenance. Gove took the money away and it was inevitable that this was going to happen… bloomin Tory Councils, eh? Same for asbestos… once maintenance stops the problems arise.
I think you will find it more complicated than that. Are you 15 y o
Local authorities love their mega project and always jump on bandwagons. Then they always cut corners on “trivial” stuff like maintenance.
RAAC is just the latest. High Alumina Cement (which rots steel) is another.
The latest school build in my town is a timber frame with glulam beams. It’s no mega project, but it went up in no time and it wasn’t a silly cost. Sadly it does have a flat roof but at least there’s no fancy concrete to spall and crack.
@@julianshepherd2038
Silly me for not using the comments section of a RUclips video for a ‘deep dive’ into the extent of the ineffectiveness of local government!
You fit in a lot of good information clearly and quickly. It's a shame mainstream broadcast news and documentary makers don't do the same.
You sir deserve a medal well done honestly absolutely superb video more like this please mate. 🙏
Absolutely well explained. We had the same with HA C remember Spghetti Junction on the M6 beig closed. ? 21:05
Does Roger Bizby have an OBE yet? he's doing more than any foot & ball player
Absolutely fantastic video. Nothing I've seen so far has come close to even explaining what it is and what the problem is. 10/10
Best explanation of RAACs I’ve heard yet. I thought I knew everything I needed to know about ‘aerated concrete’. It’s almost as if you know more about construction than politicians Roger.
What do politicians know ANYTHING about? It doesn't take a lot of sense to realize that developing one area of the country at the expense of all the rest will lead to problems. Building is just a single example. Massive pressure "darn sarf" means any short cut taking cowboy can make money. This is just the start, wait until London runs out of water and electricity!
Then you have exactly 0 knowledge of aerated concrete. There is a reason why it is used as a main construction material.
When you mentioned schools all of the same design, when I was in hospital for a few days in Berlin the staff said that they had 3 hospitals all exactly the same design and layout. They had the advantage of being able to move staff around if one of the hospitals was really busy compared to the others as they would be familiar with the layout.
architects obsession with everything being 'iconic' and governments going 'ooh standard templates for buildings, that looks communist' really has caused a bunch of problems when we could just have a lot of quality structures done for much lower cost than everything being individualised. Imagine not having a housing crisis if the government had come up with say, a dozen template options for social housing we just put up everywhere.
but they are Germans, they do it the German way, but Brits cant do it the German way, because they are to special!
@@UKTVGlod I do get it, a lot of apartment blocks put up in the 50s and 60s are just these brutalist brown cubes - and they just have a feeling of oppression about them. We wouldn't have to do *exactly* that again though. But also - if you build a new home - you can buy one off the shelf, like you see at those 'display villages', I'm sure people are perfectly happy with them.
@@frankcooke1692 yes a lot if not most homes in some countries are sold as house packages like that, it's just more affordable. not that much even just from the material side of things.. often isn't. but in a western country planning your own house to regulation and the stuff that goes under the house is kind of a massive PITA. the package has someone else make (or claim to have made) the calculations and stuff ready to go for the permits.
a custom jobbie tends to be something only someone really really rich nowadays tends to do.
that being said one of the buildings I most enjoyed living in was a a pretty brutal collection of 4 squares, like 4 apartment buildings built into one other in a connected zigzag. but I liked it enough and I liked the purpose of it. it was made as cheap housing for students - it made much more sense in that country than building 2 - 3 room apartments for students literally impossible to pay the rent for with the student benefits the students were supposed to be studying with even if you lived with your significant other(the student housing foundation just pivoted to making max money out of the housing market, basically)
edit: like 700 "apartment" doors or so in the whole complex, either 2 room or 3 rooms shared a kitchen and were an unit and toilet and you could get a whole unit or a 'cell'. it was a place that had a purpose..
Another outstanding public information broadcast by the main man Roger ! Why can't the people that have the most common sense and expert knowledge on a wide range of subjects beneficial to us ,the general public, run for office in government? If all the working class brilliant minds were to form a political party you'd win every election going !! Well done Roger, and the skill builder channel....you've got my vote 👍!!
Roger for Minister of Common Sense
"Why can't the people that have the most common sense and expert knowledge on a wide range of subjects beneficial to us ,the general public, run for office in government?"
Among other reasons: Because they don't *want* to.
This is why some people think we should replace elections, where people who want to be in Parliament try to persuade us to vote for them, with a system where people are randomly selected to sit in Parliament for a fixed term and aren't allowed to refuse.
Those people are strange, but I understand where they're coming from.
Plum chum jobs for big lying egotists mostly - they threw Alan Bridgen out for asking common sense questions - because our government all too greatly resembles "The Wizard of Oz."
How people with no relevant qualifications or experience in a particular field can be appointed to ministerial positions is utterly ridiculous.
"architects mincing about, lets just build the bloody things" had me in stitches 😅
Truer words were never spoken.
We need more masculinity, I miss it. I remember when I was a mechanic I went into work with my shorts on and one of the older guy shouted out, ‘oy, what’s those two bits of cotton hanging off your shorts?’; he was taking the mick out of my skinny legs, ha ha. The good old days.
I remember my grandfather who was a civil engineer telling an architect;
"you can't build that,"
"why not?",
"it will fall down".
The building wasn't built like that.
I remember the Aberfan disaster, 100 children and teachers died . Remember that my mum cried when the news came out ,sad sad day . Thank you Rog ,keep doing your videos. You provide a wealth of information for tradesmen and homeowner alike . All the best 👍
I did some work for Cliff Mitchelmore who was the on the spot BBC reporter on Aberfan. I remember him crying as he reported and he said he never managed to shake off those memories. Long before we started talking about PTSD there were people living with that experience who just had to get on with their lives.
Same here. We were told at school that it had happened.
Sadly, many in the construction industry don't remember Aberfan, and similar disasters such as Piper Alpha, Kings Cross fire, Clapham Junction Rail disaster, etc. The lessons are being forgotten, and "those who cannot remember the past are condemned to repeat it".
Five teachers and 109 children were killed in the school at Aberfan, in fact. Shocking!
@@DH-tv2yw The Summerland fire in 1973 here on the Isle of Man killed 50 people in less than 20 minutes due to the highly flammable nature of the Oroglass panels which covered the building. Nothing seemed to be learned from that and we then witnessed the Grenfell disaster,again caused by highly volatile exterior cladding panels.
Thanks Roger, as always 10/10 for information and entertainment, perfect to brighten up my Sunday morning housekeeping.
Ps am also a Chartered Mechanical engineer and never see any technical faults in your videos.
Thanks for the comment. I am sure I do get things wrong but I am happy to have so many viewers putting me right
Nobody has explained anything like that on the tv, excellent work.
Very impressive and infopmative video. Sadly, the politicians who were responsible for this dangerous fiasco will, as usual, not be held accountable.
That's because every politician knows - I won't be here when the **** hits the fan.
Actually it is the citizens constant demand for lower taxes drives lowest bid contracts. Politicians are not structural engineers but I’ve seen your reply over and over again. Throw the bums out… we’ll, look in a mirror
Brilliantly presented throughout with a history lesson and a little gem at the end that any comedy writer would've been proud of.
Excellent video Roger, as always.
What gets me with this situation is that so many buildings were put up that utilised products with such short lifespans. To build a school with a 30 year design life is just short-termism. Build chrap, build twice, its like they were designed to keep building companies in business! I fear though that nothing has changed...
Planned obsolescence is a thing.
I was in the first intake of a new sixth form college in 1974. It was closed in 1994 and demolished a couple of years later. The roof leaked almost from day one.
Excellent video. These are the kind of videos we need when people see something on the news and go looking for answers instead of the politicians explaining it.👍
I have shared this brilliant video to my Facebook feed for all my friends to see 👍👍
Thank you for that.
If we listened to anything politicians say we’d be truly F….
Brilliant. The content of this video illustrates the underlying problem of incompetence in the decision makers and their lack of accountability in the longer term. Ministers come and go, may have marketing, financial or legal backgrounds. Some of these skills should be transferrable but few are in post long enough to understand the job description let alone make a meaningful contribution. There is a vacuum left by people not fit for the purpose they were elected for and no way of controlling the opportunists. The DfE has spent £32 million refurbishing its office space in Whitehall this year. Good job Gill.
If only this video was shown to Parliament during todays PM Questions. Brilliant stuff 👏👏👍😀
Would gone entirely over the heads of the MPs.
It was a good point you made about old flat concrete roofs being probably coated in bitumen or otherwise something black in colour ... simply because the added attaction from solar gain would have added an element of further aging owing to the temperatures involved and higher levels of corrosion on the re-bars within the concrete itself ... clearly adding to the problem. Great video.
Indeed, all that added thermal contraction and expansion won't have helped matters.
The mad thing is that RAAC was withdrawn from use in the mid 90’s because it was discovered in the 80’s that it suffered cracking & unlike reinforced concrete RAAC is no where near as strong. Many people have heard the term concrete cancer and as you have described that just what’s happening in part. Rebar rusts expands resulting in RAAC failure. Moisture is another huge issue.
As it was announced 30+ years ago & common knowledge RAAC only has a 30 year life span it was plain and obvious this should have been dealt with and removed. Thousands of schools and thousands of other buildings were built using RAAC that should have all been replaced decades ago & it would have been far cheaper than it will now. Crazy world no excuse for this negligence . Many buildings have false ceilings so checking is not so easy. Yet all councils & Gov should know where it was used. Yes Asbestos is another huge issue. Many of the suspended ceilings we installed were to shield from Asbestos dropping. RAAC is all past its user life and been highly dangerous for decades . So far in Scotland over 35 Schools have been identified with RAAC that number will no doubt be in the thousands.
Couldn't they just re-roof the building? (I know it's nowhere near as simple as just saying it)
@@Me-zo8yc NO, its also used as flooring and walls & cladding.
The issues should have been dealt with decades ago & its just a complete cockup.
Even as late as 2018 where a school roof fell in nothing was done yet they still knew that from the report in the 80's RAAC only had a 30 year life span. Building built from the 1950's to the mid 1990's where it was withdrawn from use are all well past safe.
It comes down to not wanting to spend money and pushing it out of sight , out of mind.
Its not just schools, collages, hospitals , council & civic building its also offices its homes, like council housing, high rise buildings built in those periods probably also used RAAC.
I listened to an MP the other day saying teachers should fill out a survey after inspecting the schools for RAAC. That is the incompetence of the MP's they are clowns. It will be a very long and a very very costly fix
@@martinmorris8862 I see, thanks. 'Buy cheap, buy twice' it is then.
@@Me-zo8yc It maybe possible to remove the raac panels in a roof and put on a new roof made with timber trusses etc. Altering buildings can be difficult as you do not know what you are going to find until you start removing things.
@@martinmorris8862The problems with RAAC are different to ‘concrete cancer’. While the end result (failure) may be the same, concrete cancer is a reaction between silica and alkali, which causes expansion of the concrete and a network of micro-cracks, reducing the tensile and compressive strength of the concrete. It may result in the ingress of water and corrosion of reinforcing bar, but it is the reduction in the strength of the concrete which is the mechanism of failure.
But I have no problem with your comments regarding the seriousness of these problems, or with the fault of the government for the lack of both investment and competence.
The idea of a modular school design is extremely good. It would save huge amounts of cost all through the process and you'd end up with a much more consistent product. Design costs would be minimised, build costs would be minimised, build times would be minimised and even maintenance costs would be minimised.
But you'd still have to customise it to every school site and that school's needs, plus most new school buildings are additions to existing sites not brand new schools. So I'm not sure how this actually helps when you consider real world factors?
That's why I used the word 'modular' It means that you have standard modules that you can configure for the specific needs of the school like available footprint and number of students etc. It's like the Huf Haus system used in Germany. Fundamentally, buildings are far better off being made in a factory environment and then assembled on site. Also, I'd suggest that design cost, build cost, lead time and maintenance costs are in fact real world factors. @@hannahk1306
Excellent video which should get national coverage.
Hi. I am John 72 years old And the only Person from my whole class who is still alive. All the others have succumbed In various ways. quite a few of them have been related to asbestos. I was working with asbestos In the MO D. Which is the Ministry of Defence. And Even though we knew about the problem asbestos before I was born, Nothing was done about it until years after I was working. The result is that I am suffering from fibrous growth In my lungs and have difficulty breathing. It's a pity they didn't take all the asbestos out before we finish school.
All the best, john 👍
I second that, all the best mate. Take care
This is the best video I've seen on youtube in years. Brilliantly presented by a knowledgeable and experienced skillsman.
All those politicians say they used it because it's cheap....not bloody cheap if you have to build a new school in 30 years time 🤯🤯🤯
How would they know in advance 30 years ago? It's industry-wide and I guess contracts are awarded on the lowest costs as well...and it's not limited to schools. It's a bit like the cladding debacle when you add the media to this issue...
Exactly 💯 %
Short-term solutions for electoral votes.. totally ignorant administrative government officials! 🤬
@@guyemmott4009 ...so that's the local authorities planning offices and building inspectors...who aren't voted in...
obviously if the roof is always tight it may last 100years or more. As always a building is just as good as it's roof.
Here the saying is the lifetime of a roof is the same as it's angle
Yet they knock down the public Victorian school houses that aren’t Eton. And replace them with this shit
Every politician should be gagged and sat down in front of you, a man who knows the facts and delivers them with no frills. Well done sir!
No idea how this video got recommended to me since it's completely outside of my scope of interest or expertise, but I couldn't stop watching.
Fantastic presentation skills.
Thank you skill builder for making sense of the new scandal.
You seem to be the only one that has the intelligence to give a great comprehensive breakdown of RAAC 👏🏼👏🏼
Carry on the great work!!!
Brilliant explanation. Very clear for someone who is an average DIY-er but not knowledgable about industrial structures. Excellent. Thanks !
The council I worked for during COVID had a repair budget of 7 million per year for 250 schools. 7 mill does exactly get you very far in that kind of position. The whole budget was handled by one Council surveyor and me doing the finance on 50% time. The council was doing the best it could with limited resources, but that can only go on for so long before people and structures break completely.
Yes! 22,000 schools on a 60 year design/major rehab schedule sounds more like 400 a year than 50!
@@UK75rogerGiven RAAC last 30 years it has to be more like 800 a year, if all schools were made of it. Labour’s Building Schools for the Future programme wanted to rebuild 250 schools a year for 15 years, a total of 3,500 secondary schools in England.
@@derekjc777
I worked on BSF for 8 years (and Sure Start too). Previously in LEAs on design maintenance and planning of schools. Including 10 years at Essex, so, looking through the list, there are 2 schools I worked on....Sounds like, somewhere along the way, you may have been a colleague!
@@UK75roger I’ve never worked in LAs or in construction, I’m just informed and do research. I’m actually a Chartered electronics engineer, but standards, principles and physics are the same for all branches of engineering, so it’s relatively easy for me to understand problems, although I don’t have the training, expertise or experience to find solutions.
BTW, a friend of mine created Sure Start, Liz Taylor, and was rewarded an OBE for her efforts. It’s heartbreaking to see such a revolutionary and effective scheme ripped up by the Tories because they do not care about the poor, and believe that handing all the money to the rich solves every problem through work, and yet they do nothing to ensure workers get their fair share, and landlords and banks don’t take too much in rent and income. Instead Tories actively suppress wages and stop pay rises. Trickledown doesn’t work unless you create the paths for it to flow. Sure Start ensured the investment went to the people who need it at the bottom, whereas trickledown neoliberal economics ensures the investment goes to the people who already have way too much at the top.
I just found this channel - I like this bloke. That is an excellent logical presentation by a man who knows his stuff. Brilliant ending.
Brilliant explanation,and a great idea about standardized school building without flat roofs and all the problems that come with them ,this video should be sent to the government,it all makes perfect sense,
I worked for a company over 25 years ago and we did local council work including schools I can remember schools had a major problem with what they called concrete cancer.
I can remember having to cut off all the concrete external window cills in one school as they were crumbling away and in danger of pieces falling off and hitting someone.
I'm no expert but all the concrete ive ever been involved in laying the rebar is always full of rust surely that has to become a problem in time
@@davidmorris6841 I think that is the answer to most of these problems when you said when done properly
It’s unbelievable how this problem has been on the long finger for so long. My wife was a student nurse in what was The Greenwich District hospital a new build. 30 years later it was demolished due to what at the time was call concrete cancer! What I find incredible is that the Pantheon dome the largest unreinforced concrete dome in the world is still standing and it was built by the Romans in 126 AD yet in this day and age we still can’t get it right.
Did you watch the end of the video where I referenced the Pantheon?
All the Roman buildings that were built cheaply with their equivalent too Raac have crumbled into dust. All we see now is there best building. We can build longer lasting buildings, it just costs money.
@@SkillBuilder But imagine trying to get planning permission for a domed roof these days ...
@@SkillBuilder Pantheon : The Romans (and Greeks) were dead lucky that rebar didn't exist. Seems it's the use of rebar is the key failure here (and everywhere).
modern humans want to build things fast. fast = poor quality. its not even cheaper. its all about racing to beat everyone else. its a rat race into self-destruction and utter garbage.
Really good suggestion of having one design for schools to cut down on design costs and get the best design that works. In order to fit in with the needs of the area there might have to be a few models (some single storey, some 2 storeys, different from primary and secondary etc. But a few designs done in such a way the number of classrooms can vary would be very workable and much needed.
It's also something common in many different building types. A lot of chain businesses that use new builds have standard designs for their buildings, with variations based on the needs of the particular branch. House builders tend to have common designs, but again with variations for different property types. It's not new either. The railways were an early adopter of it, and you see a lot of stations built by the same company that are variations on a common design. It not only cuts down on design and building costs, but also maintenance, since parts are more common. It's another reason why Aldi and Lidl work well. Pretty much anything that's likely to break and need replacing during the lifetime of a shop is identical throughout the business, so they can keep a supply in stock, or just put a repeat order in for more. Layouts and equipment are also very similar so staff can transfer around the business with ease. Where I work I often travel to different locations and one of the first questions I have to ask is where things like the canteen, toilets and offices are since no two locations are alike. Even the two brand new builds I've been to are quite different in layout.
Yeah I think you could get enough variety out of some kind of modular design. How many schools do you ever go into anyway? Most students will only ever set foot in two or three different schools. Nobody would particularly notice they all look the same. There's also room for non-structural, aesthetic variations like fascia or landscaping. Demountables are already very common as classrooms - they're fine really, at least they're air-conditioned.
I came across your channel purely by accident, and because it's about something in the news, I watched it. FASCINATING!
I am not a builder, nor do I have any talents in that line, but I feel I have a much better appreciation of the issue. I learned a lot from your clear presentation and diagrams. Thanks for sharing this!
Genius. Roger you have a unique way of expressing yourself clearly, accurately, honestly and sincerely. This video is no exception, a great piece of work. Thank you.
Always rely on Roger for clarity.
Finally someone explaining the problem in an understandable way.
This guy is absolutely superb.
Years of experience mixed with a good brain. I’d take his advice over any pen pusher.
This is brilliant. Thank you - I have learned so much about this. Clear, incisive and no bull. I only wish the politicians would take the time to watch this video and act accordingly.
All right, but apart from the sanitation, the medicine, education, wine, public order, irrigation, roads, a fresh water system, and public health, what have the Romans ever done for us?
Splitter!
They made good concrete
Never in my life did I think I would find such a video interesting. In fact, I love the video: Well presented and well explained.
Hi Roger I live in Portugal and I can bet the stock video at 5:06 is from a Portuguese school!!! Yes, those roofs had asbestos, as these schools were made in the 80's and 90's with "fibrocimento" tiles. These days most of them had the roofs replaced with insulated roofs and also new windows, etc. The structure at least was well built with reinforced concrete columns and beams, prestressed floor slabs and exterior double walls with ceramic blocks and cement mortar. Us kids would sometimes break the asbestos sheets with rocks, how naive we were back then!
This man talks common sense about specialised practices and materials well worth a sub and he's really listenable, great channel .
Probably your best ever video and I’ve watched a lot, I would like to direct you to a RUclips channel that is called a different Bias! I will be putting this out on Facebook and other media platforms as not only do I believe that you are good at what you do, but you are an honest individual with lots of experience and in todays world, that is rare! 6 stars ⭐️⭐️⭐️⭐️⭐️
You sir talk complete sense as far as I'm concerned. I knew about this problem from the news but had no idea what it really meant. You have explained it exceptionally well to a layman. And the explanation of how it fails should frighten everyone who either has children going to schools with flat roofs and also the staff of said schools too. Then you go on to everyone who either works in a hospital or is a patient, or has a relative in a hospital with a flat raac roofed building. So thank you. It's very heavy food for thought for the government to try to swallow at this time.
What a brilliant video. RB at his very best!
This man makes the best building and construction programmes. He is a credit to the nation. His heart is in the right place, unlike too many in the construction industry.
Its nice to hear someone who actually knows what he is talking about explain the issue with RAAC. Thank you.
Thank you Roger. This is precisely the discussion I've been seeking for the last few days. Journalists seem to know diddly-squat (as ever).
I think it's fantastic that you take the time to produce these videos, they are so informative. Thank you!
Amazing explanation why haven't the BBC ITV SKY CHANNEL FOUR ETC ETC ETC invited you on to inform the nation end off.
Then the nation can realise that this needs sorting asap this is our future we need to look after our kids.
Remember when the government used mainstream news channels to gaslight the nation during the covid pantomine...they do not care about the kids
OUTSTANDING VIDEO. This should be compulsory viewing for all politicians, civil servants, those responsible for the safety of occupants of public buildings, and most of all, the myriad of talking heads in the media. They should all just shut up, and tell folks to watch Roger's video!
Brilliant video Roger and the team. Thanks for sharing your knowledge to all as you always do. You and your colleagues give great education, in a detailed but concise and understandable way.
Once again a brilliant explanation from SB and better clarity than mainstream media
“Architects mincing around”😂
Even a Politician could understand this explanation! Well presented Roger!
Great video, speaking as a structural engineer!
Thanks 👍
What a brilliant guy! All education ministers should be schooled (!) by him before they go anywhere taking responsibility for the buildings that our dear children study in (ignoring the equally shocking discrepancy between private and state school buildings).
Considering how many days in the year rains in Scotland 🌧 The probability of having unsafe roofs is even higher.
Does it rain is Scotland?
@@SkillBuilder Every time when I go on holidays 😅
But everything is so green! As a visiting Italian once said a few years ago; “everything is so green” Mario.
Thank you for clarifying & offering common sense to the subject. This needs to be shared with all the politicians.
Very interesting, Roger. My Dad was a civil engineer who was involved in building schools and hospitals so I can relate to this really well.
Your video should be compulsory viewing for all politicians. Excellent.
Thanks for this explanation Roger, straight and to the point
I went to Fairfields school in Basingstoke, built in 1884, still in first class condition today. It was the pride of the town at the time of its birth, Surely there is no reason why we cannot build schools and hospitals today that will last several hundred years. Obviously they would be refitted as and when to meet the current needs, but the basic structure would remain.
The costs of retrofitting are huge.
@@argonauth Not if the building was built right in the first place. Classrooms, library's, halls how do they change much? They will need decorating but that must be cheaper than replacing the roof every 40 years and worse still, putting children's lives at risk. The Victorians must be looking down at us laughing. We can't even build a safe school anymore.
@@geoffhaylock6848 when I first come to UK, I started working on the project of an hospital unit. As the project some some 10 years hold we were making 1 out of 2 surgery rooms, as the ammount of machinery has increased a lot but the speed to conduct surgeries highly doubled. Look at how the insulation and ventilation requirements has changed and you will see the cost of retrofitting. The structure is only 1/5 of the cost of such building.
My infant and primary school was brick built with a slate roof put up in the early 1900s. It still stands and whilst it is far from energy efficient it is safe. My grammar school was built in the 60s and was thrown up. Two walls of every classroom was glass (single pane). This made it very cold in winter and unbearably hot in summer and whilst it is still operating it has cost more in repairs, new window frame and flat roofs than the original cost, but at least they have somewhere to put the solar panels. As kids we used to put our feet through the asbestos panels that lined the walls and pull out the fibreglass insulation for use as itching powder. Great idea to have a standard design. A few years ago my council built a Gaelic School (yes I am now in the Highlands). The architect specified stainless steel cladding on all exterior walls. It cost a fortune but was a true land mark. Now it's an eyesore because of the weather staining on the panels.
Lochaber High School always reminded me of the Soviet Union, as seen in the movies. Grey, dull rectangular design. Some pretty poor architects in the 60s. Those concrete boxes next to the Castle in Inverness are shocking.
Yes there is some very disappointing architecture from that period.
There are very few materials that can withstand the onslought of exposure to ...WEATHER..! Heating, freezing, wet, high wind, subsidence..Tsunami.. etc etc Steel will rust.. Concrete will crack.. Timber will rot.. There is no single answer.. Monitor and Manage is the credo..
That might have been fluffy asbestos in the walls, not fibreglass 😬
Definitely fibreglass, fluffy asbestos doesn't have the itch factor, at least not on the skin.@@Jonathan_Doe_
Thank you for this very informative video. I think every person - whether that's parents whose kids go to affected schools, hospital staff or residents whose buildings have been affected - should watch this. It's very down to earth and in simple terms, no spin and no dramatic effects. I've found that most videos on this product are to alarm rather than inform.
With the issue being known about (and ignored) for years, I suspect there’s more to the timing of this “sudden crisis” than meets the eye.
My thoughts too
Excellent explanation. A copy should be sent to every politician,local and national.
Brilliant video. As an ex owner of a flat roofed commercial building, I can confirm that no matter how well constructed, sooner or later, water ingress will occur. Over a period of time, it cost more trying to cure the water ingress, than it would have cost had we had a pitched roof constructed in the first place.
Put a slanted PVC panel on top
A clear and waffle free explanation of what RAAC concrete is all about by a chap who clearly understands the building trade. Thank you Roger.
Thank you
This is one of your best videos to date
your presentation is True Public Service Broadcasting.Bravo.We need PLU.
Rodger, get this onto a dvd or similar, pop it into an envelope addressed to Mr sunak at no 10,to be watched by the cabinet, cos those idiots haven't got a clue about the real consequences of this emergency and I believe you could teach them all that they are not so bloody clever.
Well done, best explanation of the issue yet.
What did the Romans ever do for us - love it. Excellent summary
Interesting insight & passion. Flat roof design used to be very much directed by the council. My father designed an extension for the house. They demanded a flat roof. Years later, other extensions went up in our street and they were allowed Apex roofs. Our house looks the odd one out and is a constant problem as regards yearly inspection. Happily though, it is a safe roof with wooden structure. I mean, it has lasted 50+ years.
Love the reference to Life of Brian at the end.
Thank you. Really clear explanation. Shocking that school building inspectors have hidden this for several years……
Oh no, the whiteboard took me back to my Civ Eng course...and yes, an inch can make all the difference!
In my primary and junior schools, half our time was spent in portacabins...no harm done.
Politicians: "What I said were the facts as I knew them at the time..." ...They're Teflon-coated 🤣
This is absolutely brilliant. What a clear and comprehensive explaination of RAAC. And yes, why do we have flat roof buildings in the UK? My dad always moaned about having flat roofs in a wet country. It makes no sense. As Skill Builder indicates, methods that have kept structures viable for hundreds and thousands of years were used for a reason. A keystone bridge relies on precision engineering, gravity and physics. It looks like a pile of old stones stacked up in an arch and that's exactly what it is. And they stand for centuries. Of course you have to talk about the pyramids of Egypt in the same manner. There was no corner cutting. There was mass cruelty and thousands of slaves involved. But, from an architectural point of view, they were great successes. The Great Pyramid of Giza took 27 years to build and has lasted over 4,000 years. We still don't entirely understand the complexity of it's design. But penny pinching has left a rich country like ours with Third World problems in our schools and hospitals and who knows where else.
I worked with the C&A Building Department and our surveyors would never take a contract from someone who simply offered a good price. If they weren't up to standard they weren't used. If they were hired and fell below the mark they were lucky to get any further business. Everything was tendered for at least three competing companies and they had to be able to deliver the quality. Those that did earned long term partnerships with the company. In fact, over 20 years after C&A closed in the UK many of the contractors and employees still keep in contact. They know they are dealing with people they can rely on. But, under the Tories it's all about cutting costs. Do it cheap or put it on the back burner. Unless the contractor has a connection with the MP in charge of the project. Then they overspend, run late and fill their back pockets. The fact that they are putting our lives at risk doesn't bother them. Partygate showed that in spades.
Nice one Rodger you forgot to mention all the offices and high rise flats too
The offices aren't such as problem beause everyone works from home now. I was in the City of London last week. It is a ghost town.
I grew up in a family of masonry builders. I didn't pick up the trade but I did learn enough to make me wonder about some of the construction processes here in the USA such as flat roof's.
One of your old videos, two years old, popped up in my feed the other day.
It was about cracking aerated blocks. 🤔
Same here fibolites are the way forward
Such a clear, concise, direct and useful video. Gets across all the points that any concerned parent, teacher, or politician would need to know, and sadly the media don't seem to say anything about.
I don't know how Skill Builder only has half a million subscribers.
7:10 The water getting into the block, the weight will also increase significantly and so go beyond its "designed for" self load.
Saw a demo on TV recently that showed a wet aerated block is weaker in compression. Interesting to consider how a typical two storey inner course of thermolite blocks would fair in a house if exposed to a water pipe leak in the upper storey? Would the lowest blocks suffer?
I live in scotland and our kids school put a note out saying that they had an issue with this despite what our government or ministers are trying to tell everyone.
Nothing changes. Back in 1973 my school started to fall apart due to the use of high alumina cement in the concrete, added to make it harden quicker. The place was built only 10 years previously. Eventually half of it had to be demolished and rebuilt.
Did it accelerate corrosion of rebar?
"What did the Romans ever do for us?"... priceless and sums up the whole notion of modern consumerism! BRILLIANT 'OUT GAG'!!!! Well done... RB4PM!
I like your point about use of domes. Arches also. Intrinsically strong means potentially more efficient use of materials and inherent redundancy in case of material weakness.
However, as for flat roofs they dont cause spread, and are simple to design. The problem I think is we take 'flat' too literally, and they're set to quite stingy falls like 1 to 60, when we should be measuring flat roofs in degrees, and they should be 4 or 5⁰. That way you won't get ponding caused by sagging, and the chances of leaks are significantly reduced as you're not quiteas reliant on a perfect covering material.
Ease of "inspectability" should be a feature in public buildings, although might be difficult in practice.
True, no flat roof should be level
Cracking video, 100000x better then anything in the news, Can see the genuine passion and understanding
Concrete levy just begun in Ireland at the rate of 5 percent to pay for all the defective houses that contain mica in the blocks and pyrite in the under floor fill . They wanted to introduce it at the rate of 10 percent . It covers readymix concrete and concrete blocks.
Can you please tell me is this levy chargeable to all taxpayers in Ireland or just homeowners ? Many thanks.
@@amazing451 it’s chargeable on the first sale of concrete blocks or readymix concrete . in the case of ready mix concrete ,if your running a precast concrete products business and buying in readmix concrete to manufacture precast concrete products like lintels ,kerbs , wall coping ect the levy is not applied . But if your building a house and you buy ready mix concrete for foundations ect the levy will apply . The first purchaser of the concrete blocks or ready mix pays the levy . So if a builders merchant buys a thousand concrete blocks from a concrete block manufacturer the merchant is charged the levy by the manufacturer. If a house holder buys a thousand blocks direct from the manufacturer the house holder is charged the levy . The levy only appears on paper work once at the point of first purchase . If your a merchant you recoup the levy as a price rise when you sell on the thousand concrete blocks or you may opt to absorb the levy if you don’t want to raise the price of the blocks . If you recoup it as a price rise you raise the price of the blocks by 5 percent and vat at 13.5 percent is added to the purchase price which includes the 5 percent price rise .
Thanks for the brilliant explanation, they should send this video to every school in the country
Great idea on having national standard school building structures. I've always felt that McDonalds is a master the art of quickly knocking up new buildings (restaurants in their case) that have standard layouts and are (somewhat) aesthetically pleasing, inside and out. There's no reason that process can't be successfully applied to public buildings that need to be replicated in multiple locations. It also doesn't have to be just schools, they can look at hospitals and clinics etc.
There is every reason. Mcdonalds make money, lots of it. Schools don't, they cost money we don't have anymore.
McDonalds makes its money from owning land, not making burgers, they sell the building to the investor and charge them rent, but each Mcdonalds is designed for the site it sits on with the kitchen layout being the only part that is copied (even then it is not always identical). Sun path, road location, site size and shape all influence the buildings design! They have inhouse architects that know what building materials and processes they prefer to use (the cheapest and quickest, not the most sustainable or best quality)@@lksf9820
What a terrible idea!, if you do that what would become of all the planning consultants, the design committees, and the endless discussions on the important things like door handles, it would be anarchy, things might even get done within the budget !!!.☺.
Slow down khrushchev
Great explanation which should ideally be shown on BBC News. My only surprise was the bearing dimension of 75mm? I always understood it was 150mm or 6inches minimum?
I think you are correct
100mm is standard on a 100mm wall but the specification says 75mm minimum
I live in Switzerland where they know about concrete and chemistry changes. It is quite common to see old concrete structures (like the foot bridge at my local railway station) be stripped down to their rebar-reinforced core using pneumatic drills, and a new outer is cast in-situ. No doubt making it good for another 40 years. I have never seen this in the UK.
Big difference here, Switzerland is well organised and its left hand knows what its right hand is doing, and understands the value of preventive maintenance.
They actually do it using high pressure water believe it or not. I know people that worked on j6 in Birmingham. So yes they do do it here.
Excellent video and explanation.
The key issues are:
1) water ingress
2) porous concrete that allows the water to reach the reinforcement bars
3) corrosion that weakens, but moreover expands and de-bonds the reinforcement from the concrete
4) lack of visible distress symptoms
5) lack of inspection access.
There are a huge number of buildings to inspect, access to the RAAC is difficult, so how best to do this?
Why not start ON TOP OF THE ROOF with a water test?
Wherever the water ponds…
1) …is the place with the biggest risk of a historic leak…
2) …may show where a weakened beam is beginning to sag.
AND THEN go inside the building and focus on those ‘wet’ spots.
The original roof might not have been perfectly flat, but the degradation starts with the water ingress. So the “why” there is a pond is less important, I suggest only using that pond as a proxy marker for potential leaks and sagging structures.
The above approach gives a targeted approach to the most likely or most urgent areas, but that doesn’t replace a longer term need to undertake a 100% survey and to repeat those surveys regularly.
Other technology might then help: 3d laser scanning surveys allowing large roof area to be quickly surveyed and then compared on a regular basis. Local difference between the scans is an immediate indicator of movement.
Indeed continuous millimetre accurate robotic scanning is already done (eg: for settlement due to tunnelling under important structures). If a building shows some concerns (water leaks), then a continuous survey and alarm system could be instigated.
“But would that be expensive?”… “maybe yes”, but far less than the medical bills and subsequent law suit when the next child is hurt.
__________________________
Sadly, as with so many issues, speed and cost were the big factors in design and method selection. The 1960’s/70’s baby boom meant a rapid growth in the school capacity, plus they were modernising old, out of date (and very solidly built) old schools with larger, fast build, often pre-fabricated systems; with limited intended design life.
We can (and should) blame the Government, but all political parties are the same in that they are only motivated by the next election in 3-4yrs time. They are not interested in long term planning:
“what can we do, at this moment, that is cheap and just enough to fix the problem?”. If an issue isn’t widely known about (such as the Springwell school roof collapse 2018) then they’ll leave that expensive problem for whoever wins the next election to sort out.
Asbestos has been known to be hazardous from the 1930’s. However, it is a CHEAP and effective insulation; hence it was still being included in buildings, until it was finally banned in 1999 (UK).
Design was biased to the initial structural / architectural capability. Consideration of construction and MAINTENANCE did not become a required part of design until the introduction of the Construction Design and Maintenance CDM regulations 1994. Even today many designers struggle with that practical side of design.
Hence, access and ability to maintain a structure was simply not considered… Take a structure with a planned life of say 50yrs, with a first maintenance at 10-15yrs, but with NO practical method of doing that maintenance or inspection… and we have a huge problem.
My secondary school was build early 70’s and significantly expanded late 70’s. The later part was flat roof and concrete precast cladding. Certainly by the 80’s the flat roofs were leaking and receiving ad hoc repairs. Today those roofs are still being patched up.
In conclusion:
1) pitched roofs are the answer to most of the issues.
2) proper planned inspections
3) plan for and pay for long life structures
4) take any failures seriously… a little leak that makes a floor wet might be a symptom of a much, much bigger problem.
I’ll nominate you as president of the architectual society 😊😊