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A final reckoning: the future of LPS buildings under the Building Safety Act
Structural and fire safety issues in high rises built using the large panel system method of construction means housing associations face an expensive choice between remediation and demolition. Peter Apps investigates
The view from Stephen Nisbet’s living room window is extraordinary. It is a clear, bright day when Inside Housing visits and the North Sea looks as blue as the Mediterranean. He keeps a pair of binoculars on the windowsill, to watch ships on their way in and out of the Port of Sunderland, or birds at the mouth of the River Wear.
Mr Nisbet has lived in this part of Sunderland his whole life. His father was among the crew that built this 18-storey building: Londonderry Tower. With its two sister blocks, it has been a distinctive part of the city’s East End since 1968.
In a former life as a milkman, he used to make deliveries to the tower, taking the lift to the top and then working up a sweat as he navigated the narrow staircase down, milk bottles jingling in their crate.
Mr Nisbet moved in in 1997, and has lived here ever since. But perhaps not for much longer.
The landlord, Gentoo, is consulting residents on plans to demolish the building, after structural surveys deemed it unsafe in the event of an explosion. The consultation is still open, but the housing association has stopped placing new tenants in the building and the costs of safely remediating it would be extraordinary – approximately £15m.
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“I can’t fault Gentoo. I wouldn’t want the building to come down because it’s my home, but you can’t leave it up if it isn’t safe,” Mr Nisbet says.
Safety failings
Londonderry Tower is emblematic of a new phase in the post-Grenfell building safety crisis, which may be about to sweep through the country, disrupting communities and leaving social landlords with difficult, costly decisions to make. It is one of an estimated 740 high rises in England built using the large panel system (LPS) method of construction.
This style of building – popular during the postwar social housing boom in the 1950s and 1960s – involves precasting giant concrete slabs in a factory before delivering them to site. The panels are then connected together using either bolts or mortar, to form a high-rise building without the reinforced ‘skeletal’ structure of more modern designs.
“This means the wall and floor panels are dependent on the connections to each other to transfer vertical and horizontal loads safely down to the foundation,” explains David Cormie, director of resilience, security and risk at engineering consultancy Arup.
“These connections typically have very limited ability to deal with abnormal loads [such as explosions], and as the bearing length of floor panels on walls can be as little as one inch, much more modest events can cause a progressive or disproportionate collapse than in more modern reinforced concrete buildings.”
These concerns were not in the minds of builders or regulators at the time. Successive governments encouraged councils to adopt LPS, to hit housing targets quickly while limiting expenditure, as it was faster and cheaper than traditional building methods.
The potential danger manifested in 1968, when an explosion blew out a slab in an 18th-floor kitchen of the newly built Ronan Point in east London. This triggered a collapse of one side of the building, as each falling slab knocked out the one below. Four people were killed, but had the building been fully occupied, the body count would have been much higher.
In autumn 1968, the government published two circulars which required owners to strengthen buildings to ensure they could withstand pressure of five pounds per square inch (if they had gas) or 2.5 pounds per square inch (if the gas was removed).
This was effectively a requirement for a major national programme of repair works. Building owners should have immediately set to work fitting steel reinforcements and stripping out gas supplies.
But there was no oversight and no funding from the state to ensure this happened. In some cases, building owners did as they should to comply with the guidance. In some cases they did it badly. And in some cases they did nothing at all.
Today, the Building Safety Regulator (BSR) believes that just under half of the country’s LPS blocks (350) still have a gas supply, and 202 of these have no record of post-Ronan Point strengthening work. It appears that good fortune and improved gas safety regulations have been the only things keeping them standing.
It is not just gas that poses a risk to LPS buildings.
“First, shallow depth of reinforcement in the concrete means that they are more susceptible to fire-induced structural collapse, and reinforcement was sometimes left out during construction,” says Mr Cormie.
“Second, poor workmanship in the original construction resulted in a lack of weathertightness, leading to water damage, corrosion and spalling [breaking away] of concrete. This further weakens the building.
“And third, there was a lack of understanding of wind loading at the time, meaning that, in rare circumstances, buildings can be underdesigned for wind load.”
The heightened risk of fire in particular is sometimes missed: a report by CROSS-UK, an anonymous service for construction industry professionals to raise safety concerns, has noted that some structural engineers assessing LPS buildings have simply overlooked fire – asserting that this risk would be addressed by a fire engineer.
After the Grenfell Tower fire, surveys revealed structural and fire safety issues at many legacy LPS blocks (gaps between the panels can allow flame and smoke to spread between flats). Some were demolished as a result.
However, there was no nationwide strategy or effort to identify them all and ensure they were made safe.
That is about to change. The new Building Safety Act requires the ‘principal accountable person’ (a social landlord, in the case of the social housing sector) to prepare a ‘building safety case’ for the property, which is then called in for assessment. If it is deemed safe, the regulator issues a Building Assessment Certificate.
The first tranche of buildings called in include the 202 LPS blocks with gas and no record of strengthening works. It also includes those over 30 metres in height with more than 11 residential units, which captures many other LPS blocks around the country as well. At the time of writing, a total of 1,454 blocks were being assessed by the regulator.
The regulator has made 66 decisions so far, with many hundreds more due to follow in the next few months. Of the 66 decisions made so far, only 22 have passed.
This means there will be many, many orders for remediation work to bring the buildings up to standard. In the case of LPS buildings, this could be extremely costly, or impossible to achieve with residents in the building.
The reckoning around the future of these towers and the bill for fixing them, which should have arrived 57 years ago, is about to be served.
Londonderry Tower is one of 10 LPS buildings in Gentoo’s stock of social homes (inherited from Sunderland City Council in a stock transfer in 2001).
Its construction style is not the only problem. The external walls have a B2 rating for combustibility because of combustible insulation behind the rendered external cladding, which is slightly exposed due to a lack of cavity barriers around windows.
“[LPS] connections have very limited ability to deal with abnormal loads [and] much more modest events can cause a disproportionate collapse”
Gentoo has done what it can to mitigate the risks.
The building operates on a phased evacuation strategy: if a fire is detected in any flat, a tablet inside it links to an operator based in Gentoo’s head office 24 hours a day. This operator has two minutes to inquire about the cause of the alarm, and can either cancel it (if someone has burned their toast) or order escalate the alarm to the fire and rescue service.
So far, this has worked well, according to Gemma Darville, director of safety, risk and assurance at the landlord. “The local fire authority has been really supportive of that system,” she says.
Disabled residents have had “person-centred fire risk assessments” carried out, which means their needs have been assessed and adaptations put in place where necessary. They do not have full ‘personal emergency evacuation plans’, but can at least make it to a relative place of safety and await rescue if there is a fire in their flat.
The blocks have not had a gas supply for many years. Two residents with medical oxygen were rehoused to reduce the risk of explosion.
A tougher challenge is e-bikes. The fires which can result from malfunctioning batteries is a particularly serious risk in an LPS building. Gentoo has put free health checks in place with a local e-bike supplier and the local fire service and is looking into the feasibility of outside charging facilities.
Demolition or remediation?
What of the long-term future of the tower? Gentoo initially took advice from the Building Research Establishment (BRE) about what needed to be done to the block, and then appointed the engineering consultancy Ridge to advise further, with Arup, another engineering firm, enlisted to peer review their work.
The BRE handbook on assessing LPS buildings, published in 2012, says they can be deemed safe if they pass any one of three tests. These look at the quality of ties between the concrete panels, their ability to withstand sudden unexpected shocks, and their general robustness against collapse.
Assessment is difficult. It means intrusive surveys which involve stripping back a flat and cutting into the concrete. This can’t be done with residents present, so the housing association either needs to move people out or wait for the homes to become vacant. This must be done in different areas of the building.
Gentoo completed these surveys in 2024, at a cost of £1m. Londonderry Tower failed on all three counts and is vulnerable to collapse in the event of significant “accidental loading”, like an explosion.
Inside Housing visited one of the surveyed flats. In the bare room, the strengthening works carried out in the 1970s are visible: a relatively flimsy looking L-shaped steel bracket bolted to the ceilings of the flat, with some of the bolts missing.
After the survey, the landlord faced a decision on whether to evacuate the building immediately.
“We had to balance the disruption of moving people immediately against the risk and the measures we put in place to limit the chances of an explosion,” says Stephen Flounders, executive director of regulatory and business services at Gentoo.
“It would be a completely different story if we still had gas. Gas explosions happen, you can never completely rule them out. I don’t know how we could ask people to keep living here if there was still a gas supply.”
In the longer term, the buildings would need to be strengthened if they were to remain occupied.
Steel bars would need to be added vertically and horizontally across the ceiling every 600mm in every room of every flat in the tower, and then covered over. Residents would need to move out while this was done. The cost would run into the tens of millions, and take years to complete. As a result, the landlord is consulting on proposals to demolish the towers.
Currently, 163 of the 201 flats in this block and its two sisters are occupied.
“We have got 19,000 people on our waiting list, so if we do decide to demolish these towers, that will mean people who have been waiting for a while will have to wait longer,” says Ms Darville.
The tower blocks look old, but they are still a functioning community. People know and look out for each other; a resident runs a not-for-profit cafe on the ground floor, which serves as a community hub.
“You can never rebuild the same community, and that is something we are really mindful of,” says Ms Darville.
“We will do our best to keep that together. If people are saying to us they have a best friend or carer on the same floor as them, we would want to consider that.”
This building is one of the lowest-risk properties the regulator will deal with (it has no gas and evidence of at least some strengthening works). And the building has no leaseholders, which simplifies the rehousing process and keeps costs lower.
For other buildings, a much quicker decision might need to be made about rehousing. Mr Cormie says building owners should take note of warnings if a building is performing badly.
“Poor weathertightness of the joints between panels, and air movement, moisture ingress, water ingress, mould and condensation are key indicators [of problems]. None of these would indicate an imminent risk of collapse on their own, but could indicate degradation of the concrete, or corrosion of reinforcement that increases the risk of collapse,” he says.
“In some cases, there are reports of joints being large enough that residents resorted to stuffing them with newspaper to keep out the wind. Large cracks that appear over a short period of time, or structural movements that might lead to doors sticking, for example, would be signs of a more immediate concern.”
The BSR cannot prohibit the occupation of a building, but it can alert the local fire authority to concerns.
“We have found a few cases where we’ve needed to take action urgently,” says Andrew Saunders, operational policy advisor at the BSR. “That’s mostly to do with fire spread, although there have also been buildings where we’ve been concerned about disproportionate collapse.”
Since the Grenfell fire, a number of buildings have been evacuated quickly, including Barton House in Bristol. This was described as a “mass traumatising event” by medics who interviewed the residents.
They displayed anxiety, low mood and hypervigilance, a symptom commonly seen after traumatic events. Residents’ physical health also suffered, with researchers reporting worsening respiratory disease, skin conditions and “debilitating impacts on sleep and eating”.
Others displaced by this sort of event have faced up to a year in temporary accommodation as they wait for a new home.
So far, the BSR has given four determinations for LPS buildings. Three have been refused and one approved. This is a small sample size, but it is likely that many other LPS buildings will face a choice between demolition and extremely expensive remediation works.
“We desperately need a national strategy for these buildings,” says Mr Flounders of Gentoo.
“We need to work out what the offer is to residents for rehousing, and we need some consistent guidance about what the tolerable level of risk can be. The sector is still working from circulars written in the 1960s.”
“We also need to talk about funding and how this is going to work, because if the expectation is just going to be that social landlords pay for everything, there will be knock-on impacts from that.”
Gentoo has convened a sector-wide working group for providers with LPS buildings, which Arup and Ridge support. The last session had more than 50 attendees. But while sharing information and best practice will help, government action is required.
It may also be the last chance to act before a major disaster. Climate change is driving heavier rainfall and hotter summers, which cause expansion and place increased pressure on the joints.
In 2021, a building collapse in Miami, partially caused by water ingress corroding the reinforced steel, killed 98 people. We have gone 57 years since Ronan Point collapsed without a repeat. There may not be many years left.
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