Use of RAAC in UK railway buildings

[Guest]

With the growing hoohah about RAAC in schools, hospitals, courts etc is there any sense of how exposed the railway is to the risk? 

 

Given the timescale in which RAAC was used is wholly within the period during which railways were in public ownership, it would seem unlikely that railways escaped its use? I would imagine that staff mess facilities and similar structures thrown up quickly and cheaply in the heyday of Modernisation will be obvious candidates for its use.

 

The CLASP style of building was prevalent for a while in depots and stations - what roof construction did they use?

[woodenhead]

RAAC appears to have a lifespan of about 30 years - it's still in schools and hospitals due to woeful investment to replace cheap buildings which is effectively chickens coming home to roost for successive Governments who must have been aware of a ticking timebomb of cheaply constructed buildings needing replacing.

 

For the railways, you have to imagine perhaps some buildings may have used it, but the general shrinking of the railway since the 1980s - loss of loco depots, freight yards, stabling points etc and the move to man in van has probably seen most buildings that may have been suitable for RAAC (if at all) fall out of use and probably get demolished.

 

By it's very nature of not being a long term material, I would imagine it will not have been used on anything that carries trains or carries structures over trains.

[Guest]

I’m almost certain it wouldn’t have been used in structures such as bridges as it wouldn’t have the right structural properties. It’s a material intended for relatively light loads.

 

I agree that many of the depots and other structures using RAAC might have been demolished or renewed, but CLASP-style structures do remain and there are still many flat-roofed structures from the period at stations around the country. It is the sort of material that might be used for station/platform canopies as well.

 

Given the 000s of public sector buildings (schools, courts, hospitals, libraries) that still appear to have this form of construction, it would seem unlikely that the railways are unaffected.

[The Stationmaster]

As RAAC is not strong enough for structural use I'd be surprised if it was used for roofs unless it was given a lot of supports pluss a substantial covering to make it weather proof.  It seems to have been used in ceilings and wall panels.

 

Most of the 'quickie' railway buildings were either BR built timber structures - such as the 'Cathays cabin' used mainly for PerWy staff on the WR - or Portacabins in various sizes and styles used for all sorts of jobs  which were quick and cheap to install and later remove.  The only likely RAAC use I van think of is possibly internally in CLASP buildings; possibly in some of the various tower blocks used for admin and managerial centres, and  maybe in the large panel signal boxes although I've not heard of any of them falling apart  even though quite a number have managed a 60 year life.

[Guest]

Thanks @The Stationmaster I’ve certainly heard in news reports of hospital roofs being no-go areas due to RAAC construction and the issues being worsened by poor waterproofing (how many flat roofs before the 90s are actually watertight!?). Possibly the BR architects had no truck with such nonsense materials and did their own thing and it’s not a problem.

 

I worked in the led BR building in Birmingham (recently demolished) but that was extensively refurbished in the late 90s. In fact I wonder if that’s a common thread - after privatisation many BR buildings (E.g. RTC in Derby) were likely extensively refurbished and modern standards applied before being let to new tenants. Or else they were demolished and redeveloped, if not structurally sound. Privatisation coincided with RAAC falling out of favour.

 

Stations built in the 60s like Wakefield Westgate, Tamworth, Lichfield etc have mostly been redeveloped I think.

[BR60103]

I'd never heard of RAAC. But the following in a BBC post:

 

It is aerated, or "bubbly", like an Aero chocolate bar.

But it is less durable and has a lifespan of around 30 years.

 

I didn't realise what Aero's best before date was.

 

[Darius43]

11 hours ago, Gatesheadgeek said:

 Possibly the BR architects had no truck with such nonsense materials and did their own thing and it’s not a problem.

 

That should be: “…the BR Civil and Structural engineers had no truck…”

 

Cheers

 

Darius

[Darius43]

As stated above RAAC is unlikely to have been used in permanent way civil engineering structures but may well, in the form of lightweight precast concrete floor and roof planks, have been used to make the floors and roofs of railway offices and other accommodation buildings - as The Stationmaster has pointed out.

 

This is a potentially massive problem and alas, once more, the response of those with responsibility appears to be that of reputational protection rather than seriously attempting to rectify the situation.

 

Darius

Edited September 4, 2023 by Darius43

[Joseph_Pestell]

The people responsible for our public sector don't really have much knowledge or experience of practical matters like building. It seems extraordinary that anyone would specify a material with a 30-year life expectancy to put in a publicly-funded building, a totally false economy.

The Govt ministers commenting on the media seem to have no understanding of how long this is going to take to solve or indeed what it will take. One can not just replace a floor or a ceiling like that. It will have structural consequences on the whole building. Likely result is total demolition.

And, of course, this is not just schools, hospitals, etc.  There will be private sector housing, offices also affected and needing scarce building resources to remediate.

Finally, to bring back to the railway, the most likely buildings to be concerned would be signal boxes. We could see huge disruption to train services if a signal box at a key location is found to be in danger of a roof collapse.

[APOLLO]

Not railway but I visited my sister in Queen Elizabeth Hospital Kings Lynn in March. A vast rambling mainly 2 storey 1970's building. The roof of the first floor ward she was on was shored up with boxed in props and beams. QE hospital is on the list of those seriously affected, replacement cost up to £1.5 Billion.

 

More than a tad concerning is this issue. Been known about for a long time also.

 

Brit15

[Compound2632]

35 minutes ago, Joseph_Pestell said:

It seems extraordinary that anyone would specify a material with a 30-year life expectancy to put in a publicly-funded building, a totally false economy.

 

I should think it has been a case of "cheaply, or not at all" since we all know that to do the job without resort to false economy would require a higher rate of taxation and politicians understand perfectly well that the electorate is as interested in short term financial gain as any capitalist.

[Michael Hodgson]

Railway engineering is always big and heavy.  Cast iron is good (admittedly not in bridge way beams)

Anybody with the temerity to suggest the concept of using "lightweight concrete" would have received short shrift.

[The Stationmaster]

4 hours ago, Darius43 said:

That should be: “…the BR Civil and Structural engineers had no truck…”

 

Cheers

 

Darius

No - the BR Architects because they would be the one specifying the materials to be used in BR designed buildings.  Buildings designed by contractors or rented/leased from outside developers would not necessarily have involved any BR staff in their design and construction.

 

For example one twoer block I worked in had sold reinforced concrete floors but for all I know the ceilings might have used RAAC panels (the walls definitely didn't as they were all solid blockwork although it might well have been AAC blocks (not quite the same thing as RAAC).  But as that 1960s building has fairly recently been demolished it clearly took a heck of lot of effort to dismantle it although for all I know the ceilings might have been easy to rip out.

[The Stationmaster]

1 hour ago, Compound2632 said:

 

I should think it has been a case of "cheaply, or not at all" since we all know that to do the job without resort to false economy would require a higher rate of taxation and politicians understand perfectly well that the electorate is as interested in short term financial gain as any capitalist.

Was it cheaply or was the material used because it was fire resistant or for some other reason?  Cost would undoubtedly have played a part but it wouldn't have been the only factor.  For example in some situations RAAC panels would no doubt have been an alternative to asbestos or Asbestolux panels because of its insulating properties.  

[Bucoops]

35 minutes ago, The Stationmaster said:

Was it cheaply or was the material used because it was fire resistant or for some other reason?  Cost would undoubtedly have played a part but it wouldn't have been the only factor.  For example in some situations RAAC panels would no doubt have been an alternative to asbestos or Asbestolux panels because of its insulating properties.  

 

It's only been briefly touched on in the news but is gaining traction if you pardon the pun, but many of the buildings that used it in the 50sand 60s had spray asbestos insulation added - largely removed now but as it is impracticable to remove it from between the joints, they were frequently filled with sealant. So removing RAAC from these buildings is going to be complex and expensive.

[Mark Saunders]

3 hours ago, Michael Hodgson said:

Railway engineering is always big and heavy.  Cast iron is good (admittedly not in bridge way beams)

Anybody with the temerity to suggest the concept of using "lightweight concrete" would have received short shrift.

The last major concrete problem I recall was High Alumina cement with the reaction between the steel reinforcing and the alumina!

[Darius43]

3 minutes ago, Mark Saunders said:

The last major concrete problem I recall was High Alumina cement with the reaction between the steel reinforcing and the alumina!

Not really.  The in-service mineralogical conversion of the HAC reduced the concrete strength and its resistance to chemical attack, which would have affected the rebar.

 

There was also Alkali Silica Reaction (ASR) , which was a big issue in the 1980s when I started my civil engineering career and then Thaumasite in the early 2000s.

 

There’s always something…

 

Cheers

 

Darius

[Compound2632]

The moral is, if you use new types of materials, you should be budgeting to replace them in 30 years' time. Since public expenditure is funded by current taxation (or borrowing), the prudent thing to do would be to maintain taxation at the rate it was at at the time. 

[Joseph_Pestell]

21 hours ago, Compound2632 said:

 

I should think it has been a case of "cheaply, or not at all" since we all know that to do the job without resort to false economy would require a higher rate of taxation and politicians understand perfectly well that the electorate is as interested in short term financial gain as any capitalist.

 

"Not at all" might have been the better option in this case.

 

I suspect that there has been some slightly inaccurate reporting by overeager journalists. I can't see why the concrete would not last indefinitely if kept dry.  The issue (30-year life) is about roof coverings (roofing felt + tar) not having done its job, allowing the concrete to contain water. As the concrete planks then sag, the situation becomes even worse as any water will pool rather than run off.

 

Personally, I am completely against flat roofs in our climate. Even around the Med, they give endless problems.

[Ohmisterporter]

All the discussion about RAAC has been in public buildings; has none been used by the private sector? 

[Compound2632]

32 minutes ago, Joseph_Pestell said:

"Not at all" might have been the better option in this case.

 

What, not have schools and hospitals etc.?

[Oldddudders]

17 minutes ago, Ohmisterporter said:

All the discussion about RAAC has been in public buildings; has none been used by the private sector? 

Possibly, but they aren’t a Government issue, so no chance of a call on HM Treasury. 

[Joseph_Pestell]

22 minutes ago, Compound2632 said:

 

What, not have schools and hospitals etc.?

 

No, stick with the old ones until a better method was found.

[Compound2632]

Just now, Joseph_Pestell said:

No, stick with the old ones until a better method was found.

 

No, I think if you look into it, you will see that that just wouldn't do: overcrowding and inadequate facilities. The point is that in the short term, we got what we needed at a price we were prepared to pay. The problem is that now, we are not prepared to pay - just look at the basic rate of income tax now compared to 45 years ago.

[ruggedpeak]

RAAC was primarily used for large span open spaces in buildings such as school halls and gyms and hospital operating theatres, but was also used in other settings.

 

RAAC normally sits between the external roof finish and the internal ceiling finish. This means in most settings you can't see it or its condition, and need an intrusive survey to assess it. As the external finishes also weather and deteriorate water ingress is likely. Due to the nature of this stuff even if you can see it you can't be sure as to its condition. The added bonus is often you have to cut through asbestos containing materials to get to it!

 

Spontaneous colllapse and a mass casualty/fatality incident involving children is a realistic possibility, although the powers that be had downplayed this until this week for reasons best known to themselves.

Edited September 5, 2023 by ruggedpeak
typo/edit