Q&A
1. What is LPS?
LPS stands for Large Panel System.
LPS buildings typically comprise precast reinforced concrete floor and roof components spanning onto storey high structural precast concrete wall panels, which are generally of plain concrete or lightly reinforced concrete.
(Source: The Structural Engineer magazine, August 2012 https://www.istructe.org/journal/volumes/volume-90-(2012)/issue-8/technical-guidance-notes-structural-assessment-of/)
Its use has included high-rise structures such as flats, but also maisonettes and other multi-level structures.
2. How many LPS buildings are there?
There is no central register, but The Guardian reported on 16 November 2023 that LPS was present in 575 tower blocks across the UK.
(Source: “Tenants and campaigners estimate there are about 575 LPS tower blocks still standing after construction mostly in the 1950s and 60s.” https://www.theguardian.com/society/2023/nov/16/experts-warned-government-of-tower-block-collapse-risk-last-year-leak-reveals)
3. What issues are there with LPS?
Issues with LPS can include lack of robustness, poor design and construction generally.
(Source: Assessing higher-risk buildings under the Building Safety Act: a compendium of structural typologies; IStructE, 2024: https://www.istructe.org/resources/guidance/assessing-higher-risk-buildings-under-the-building/. Also link below Appendix 1 for the relevant section on LPS).
Building safety regulations and requirements changed in the late 1960’s due to the collapse of the southeast corner of Ronan Point, a 22 storey LPS high-rise in east London. The collapse was due to a piped gas explosion on the building’s 18th floor which the building’s structure did not withstand.
Accidental loads and incidents of sufficiently large magnitude – such as internal or external gaseous explosions, fire or vehicle impacts – can cause local damage to load-bearing components.
(Source: https://www.istructe.org/journal/volumes/volume-90-(2012)/issue-8/technical-guidance-notes-structural-assessment-of/)
4. Are they safe?
LPS became popular in the UK post World War II, and especially in the 1960s. Therefore, maintenance and regular assessments are essential to ensure safety.
For example, a 2011 CROSS UK report advised: “It is good practice for LPS buildings to have a recorded structural history. Their condition and continued structural integrity should be monitored.”
(Source: https://www.cross-safety.org/uk/safety-information/cross-safety-report/large-panel-system-lps-building-structural-201)
A 2012 article in The Structural Engineer says that “It is important to recognise that overall the historic structural performance of LPS dwelling blocks has been satisfactory with most of the blocks which still exist having been in service for over 40 years.”
(Source: https://www.istructe.org/journal/volumes/volume-90-(2012)/issue-8/technical-guidance-notes-structural-assessment-of/)
To assess safety, a full inspection needs to be done by a professionally qualified structural engineer.
5. Should gas be turned off in LPS high rise blocks?
We can trace concerns about gas and LPS buildings back to Ronan Point, a high rise building that partially collapsed in May 1968 due to a gas explosion.
The conclusion of the Ministry of Housing and Local Government 1968 Inquiry into the accident was an important benchmark. Amongst its recommendations, it said that: "In blocks that are judged to be susceptible to progressive collapse, measures must be taken to strengthen them to eliminate this risk, and the gas supply should be turned off until this has been done (paragraph 191)."
(Source: “Report into the inquiry into the collapse of flats at Ronan Point, Canning Town” by the Ministry of Housing and Local Government; p. 63 “Recommendations for existing tall buildings.” https://archive.org/details/op1268013-1001/page/n7/mode/2up).
Post Ronan Point, recommendations stated that new blocks must be designed so that they are not susceptible to disproportionate collapse (p.64): "(32) Designers of new blocks must design the building so that it is not susceptible to progressive collapse, paying particular attention to introducing continuity at the joints and so disposing the load-bearing walls that alternative paths are provided in the event of a local failure (paragraoh 188)."
Following concerns about the Ledbury Estate in London, the 2017 government issued a letter about the safety of LPS with piped gas, to directly affected councils. This stated: “In light of these findings from Southwark, you should ascertain whether buildings with large panel systems in your area also have piped gas. If they do, you should take action to ensure that these buildings can carry piped gas safely. You may want to take expert advice to assure yourselves of this.”
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https://assets.publishing.service.gov.uk/media/5a82d04640f0b62305b947c7/170811_Letter_from_Tamara_Finkelstein.pdf
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https://www.gov.uk/government/publications/letter-regarding-the-safety-of-large-panel-system-buildings-with-piped-gas-18-august-2017 - letter to Southwark Council about the Ledbury Estate.
This DLUHC guidance says that immediate assessment is required, and this is a common short-term approach. A case-by-case approach is necessary.
6. Should LPS buildings be demolished?
Landlords need to assess their buildings in line with the new Building Safety regime. Risks need to be assessed on a case by case basis and mitigated, possibly by strengthening. Some authorities have found active management of risks and decanting to be the most cost-effective and least disruptive option in the long run compared to strenghtening and refurbishment. Even if this is adopted, given the sheer number of HRBs to be inspected, it may take some time to decommission all LPS buildings.
7. Does a HRB need a Building Assessment Certificate (BAC)?
No. DLUHC guidance states: “A high-rise residential building does not need a BAC before people can live in it.”
However, it states that a certificate is needed for “large panel systems built between 1957 and 1973 with a gas supply, and it is unclear if reinforcement work has been carried out.”
https://www.gov.uk/guidance/preparing-a-building-assessment-certificate-application
8. What are the current risks posed by non-piped gas in LPS?
There is still a risk from smaller explosions and as stated above, potential risks need to be addressed on a case-by-case basis.
9. Should the government pay? Who pays for this?
Historically, the government did contribute to remediation, but this was a while ago in the 1970s.
This is now a long term-term problem that needs to be addressed as there is a legal obligation to resolve it – the new Building Safety regime “places legal responsibilities on those who participate in the design and construction of higher-risk buildings, commission higher-risk building work and those who are responsible for managing structural and fire safety in higher-risk buildings when they are occupied.”
(Source: https://www.gov.uk/government/consultations/consultation-on-implementing-the-new-building-control-regime-for-higher-risk-buildings-and-wider-changes-to-the-building-regulations-for-all-buildings/outcome/government-response-to-the-consultation-on-implementing-the-new-building-control-regime-for-higher-risk-buildings-and-wider-changes-to-the-building-re)
The overall costs have not been estimated. However, landlords with large LPS portfolios may have significant costs – works to comply with legislation need to be funded. (See background research by University of Reading: “Friends in high places: government – industry relations in public sector house building during Britain’s tower block era”, P. Scott, 2020).
10. What else has IStructE done to help with the understanding of LPS?
We have highlighted concerns regarding LPS and provided structural engineering advice on assessment through guidance, publications, webinars, and courses to ensure our members (and non-members) are fully aware of the issues. Our aim is to ensure that safety is central to the future policy decisions and that views of structural engineers are represented.
The most recent guidance is available on our website and bookshop.
11. What else is being done to manage LPS risks?
The BSR, the new body for the safety and standards of buildings, are prioritising this issue (see Construction News, 23 January 2024: https://www.constructionnews.co.uk/health-and-safety/why-is-the-building-safety-regulator-acting-on-large-panel-systems-23-01-2024/).
IStructE courses
Publications / research
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IStructE (1989) Guidance note on the security of the outer leaf of large concrete panels of sandwich construction. London: IStructE
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Cooke, G. ‘Large sandwich panel fire resistance assessment’. The Structural Engineer, 83(19), 4 October 2005, pp18-21
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The Institution of Structural Engineers (2010). Appraisal of existing structures. 3rd ed. London: IStructE Ltd
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The Institution of Structural Engineers (2023). Structural robustness and disproportionate collapse in buildings. 2nd ed. London: IStructE Ltd
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Structural Assessment of existing large panel system built dwelling blocks for accidental loads, The Structural Engineer magazine August 2012 https://www.istructe.org/journal/volumes/volume-90-(2012)/issue-8/technical-guidance-notes-structural-assessment-of/
Relevant CROSS Reports (Collaborative Reporting for Safer Structures UK).
PDF files of further articles and BRE items: