TLDR you limey bastards built school roofs out of a material that was advertised as with a 30 year life span, and here we are 40 years later and its surprised pikachu faces all around.
It’s not clear to me from the article whether it was expected to only last 30 years at the time, or whether it was subsequently revised down in some way.
I mean, my guess is that many building materials may only guarantee some number of years, but it may be the norm for them to last longer. I assume that businesses selling stone do not rate, say, masonry for hundreds of years, though it clearly can last that long.
The article has:
Raac, a lightweight building material, was commonly used in panel-form in public building construction from the 1950s to mid-1990s. It is estimated to have a lifespan of 30 years, and many structures have now passed that age.
EDIT: Yeah. From another article, it sounds like at the time it was built, it was not realized that the material would last only 30 years:
During the post-war building boom of the 1950s, 60s and 70s, reinforced aerated autoclaved concrete (RAAC) was something of a wonder material.
In the 1990s, when the material was still being used, structural engineers discovered that the strength of RAAC wasn’t standing the test of time.
The porous, sponge-like concrete - especially when used on roofs - could easily absorb moisture, weakening the material and also corroding steel reinforcement within.
As it weakened, it sagged, leading to water pooling on roofs, exacerbating the problem.
RAAC made in the 1950s was at risk of failure by the 1980s, the report concluded.
About 30 years ago, it became known that the lifespan of RAAC in many public buildings, including hospitals and schools was no greater than 30 years.
Some of the buildings constructed using RAAC were only intended to be temporary structures, regardless of the knowledge of the material’s true lifespan.
The Queen Elizabeth Hospital in Kings Lynn for example, was opened in 1980 and was intended to last only 25 years. But it is still being used today, 43 years later. It is finally being replaced, but only after it’s RAAC roof started to fail and had to be held up by hundreds of temporary supports.
Buildings like this would have been replaced long ago if consecutive governments had not failed to properly invest in our public infrastructure.
And timber frames are only manufacturer rated for 30 years.
The Americans have been using them for decades, while in the uk we’ve only started to accept them recently.
My parisian building is timber framed (as many are in the city) and was built around 1860. We replaced the damaged wood this year, and it should be good for another 150 or 200 years.
You’re aware Europe has the oldest timber framed buildings and the us took their building lead from old Europe.
You act like Europe decided stone was the better solution when that’s just not true, Europe by in large deforested itself into leaving stone as the only affordable solution left and only then switched off timber framed homes.
I’m surprised there’s not more academic papers about the effect of shipbuilding on global forests. Farming is probably a bigger factor but shipbuilding is responsible for a weirdly huge amount of old growth.
Source for 30 year rating? I’m not aware of such in either Europe or North America. I found a few sites reporting that number but couldn’t find an actual authority giving that rating.
Also, there’s a difference between a wood (or stick) frame and a timber frame, at least if you’re including North America in context. In our terminology, a timber frame has large timber beams and columns supporting the load, and dividing walls are put in between. A stick frame house uses smaller lumber studs, and most of the internal and external walls are supporting the floors or roof above.
American houses are stick frame, and with proper maintenance a stick frame house can last easily over 100 years. Wood doesn’t rot if treated and maintained properly. Settling of the foundation is a bigger problem, and simply subject to ground conditions which would impact even a steel frame house.
Timber frame is becoming more popular again for large buildings though, since ~12"/30cm timber columns have pretty good fire ratings, can support 3-4 stories, and are good carbon sinks for more environmentally friendly construction versus concrete or steel. My city is putting up some 3 story timber apartment buildings that look pretty awesome.
Long story short, wood is a great, renewable construction material if you’re smart about how you build with it and how you treat it.
30-45 years is what the frame manufacturers would give in guarantees, or expected life. Which is possibly why some mortgage providers class timber frame as non-standard construction.
In terms of actual age, the numbers I found suggest that properly maintained softwood frames can last in excess of 80 years.
I do kind of wonder whether it would have been cheaper to, back then, go through and seal all of this stuff against moisture, if that is possible. It sounds like what kills it is exposure to moisture.
If they’re already starting to collapse and inspections are finding a lot of instances of degraded concrete, though, I assume that it’s too late for that.
EDIT: It also sounds like the stuff has been widely used in mainland Europe, not just the UK. I don’t know whether the UK being particularly rainy might be a factor, but if the UK is seeing serious problems now, then it might be worth taking a look at usage in mainland Europe as well.
RAAC was used in roof, floor and wall construction due to its lighter weight and lower cost compared to regular concrete,[1] and has good fire resistance properties; it does not require plastering to achieve good fire resistance and fire does not cause spalls.[2] RAAC was used predominantly in public-sector construction in Europe, in buildings constructed since the mid-1950s.[3][4] RAAC elements have also been used in Japan as walling units owing to their good behaviour in seismic conditions.[5]
Reading some other articles, it sounds like we in the US and the Canucks do have some as well, but not much, mostly because apparently wood is cheaply available and dominates as a material, and the American construction industry isn’t very familiar with use of AAC. There is only one small (13 person) US factory that produces the stuff, in Haines City, Florida.
It’s no secret that autoclaved aerated concrete (AAC) has struggled to gain a foothold in North America. AAC is in widespread use in Europe, Mexico, and much of the world, but it has had trouble competing against wood-frame building here in the United States and Canada.
I couldn’t find reference to specifically the reinforced form (RAAC) in the US, but looking at the factory’s webpage, they list reinforced AAC roof panels as one variant that they can provide, so I assume that they must have sold some.
TLDR you limey bastards built school roofs out of a material that was advertised as with a 30 year life span, and here we are 40 years later and its surprised pikachu faces all around.
It’s not clear to me from the article whether it was expected to only last 30 years at the time, or whether it was subsequently revised down in some way.
I mean, my guess is that many building materials may only guarantee some number of years, but it may be the norm for them to last longer. I assume that businesses selling stone do not rate, say, masonry for hundreds of years, though it clearly can last that long.
The article has:
EDIT: Yeah. From another article, it sounds like at the time it was built, it was not realized that the material would last only 30 years:
https://news.sky.com/story/the-once-wonder-material-reinforced-aerated-autoclaved-concrete-will-cause-chaotic-start-to-academic-year-12951727
Some of the buildings constructed using RAAC were only intended to be temporary structures, regardless of the knowledge of the material’s true lifespan.
The Queen Elizabeth Hospital in Kings Lynn for example, was opened in 1980 and was intended to last only 25 years. But it is still being used today, 43 years later. It is finally being replaced, but only after it’s RAAC roof started to fail and had to be held up by hundreds of temporary supports.
Buildings like this would have been replaced long ago if consecutive governments had not failed to properly invest in our public infrastructure.
And timber frames are only manufacturer rated for 30 years. The Americans have been using them for decades, while in the uk we’ve only started to accept them recently.
My parisian building is timber framed (as many are in the city) and was built around 1860. We replaced the damaged wood this year, and it should be good for another 150 or 200 years.
It all depends how you build.
Damn socialist Frenchies with their… checks notebook timber framed buildings
You’re aware Europe has the oldest timber framed buildings and the us took their building lead from old Europe.
You act like Europe decided stone was the better solution when that’s just not true, Europe by in large deforested itself into leaving stone as the only affordable solution left and only then switched off timber framed homes.
The UK does import timber, though I imagine that greater distance adds cost.
https://www.eastcoastfencing.com/news/where-does-most-timber-in-the-uk-come-from
Says that Sweden is currently the largest single source.
Correct, they import timber now.
I’m surprised there’s not more academic papers about the effect of shipbuilding on global forests. Farming is probably a bigger factor but shipbuilding is responsible for a weirdly huge amount of old growth.
Source for 30 year rating? I’m not aware of such in either Europe or North America. I found a few sites reporting that number but couldn’t find an actual authority giving that rating.
Also, there’s a difference between a wood (or stick) frame and a timber frame, at least if you’re including North America in context. In our terminology, a timber frame has large timber beams and columns supporting the load, and dividing walls are put in between. A stick frame house uses smaller lumber studs, and most of the internal and external walls are supporting the floors or roof above.
American houses are stick frame, and with proper maintenance a stick frame house can last easily over 100 years. Wood doesn’t rot if treated and maintained properly. Settling of the foundation is a bigger problem, and simply subject to ground conditions which would impact even a steel frame house.
Timber frame is becoming more popular again for large buildings though, since ~12"/30cm timber columns have pretty good fire ratings, can support 3-4 stories, and are good carbon sinks for more environmentally friendly construction versus concrete or steel. My city is putting up some 3 story timber apartment buildings that look pretty awesome.
Long story short, wood is a great, renewable construction material if you’re smart about how you build with it and how you treat it.
30-45 years is what the frame manufacturers would give in guarantees, or expected life. Which is possibly why some mortgage providers class timber frame as non-standard construction.
In terms of actual age, the numbers I found suggest that properly maintained softwood frames can last in excess of 80 years.
Oh, bummer.
I do kind of wonder whether it would have been cheaper to, back then, go through and seal all of this stuff against moisture, if that is possible. It sounds like what kills it is exposure to moisture.
If they’re already starting to collapse and inspections are finding a lot of instances of degraded concrete, though, I assume that it’s too late for that.
EDIT: It also sounds like the stuff has been widely used in mainland Europe, not just the UK. I don’t know whether the UK being particularly rainy might be a factor, but if the UK is seeing serious problems now, then it might be worth taking a look at usage in mainland Europe as well.
https://en.wikipedia.org/wiki/Reinforced_autoclaved_aerated_concrete
Reading some other articles, it sounds like we in the US and the Canucks do have some as well, but not much, mostly because apparently wood is cheaply available and dominates as a material, and the American construction industry isn’t very familiar with use of AAC. There is only one small (13 person) US factory that produces the stuff, in Haines City, Florida.
https://www.resilientdesign.org/aac-an-ideal-material-for-resilient-buildings/
I couldn’t find reference to specifically the reinforced form (RAAC) in the US, but looking at the factory’s webpage, they list reinforced AAC roof panels as one variant that they can provide, so I assume that they must have sold some.
More like getting on for 60 years in some cases.
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