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CROSS Safety Report

No worse than existing?

Report ID: 1148 Published: 17 February 2023 Region: CROSS-UK


This report discusses the perceived exploitation of a common fire safety argument: the existing condition.

Key Learning Outcomes

For Designers, Fire Engineers, and Building Control Officers:

  • Proposals to alter buildings without applying safety measures that would be required in a new building, by relying on the argument that the building will be no worse than existing, should be carefully considered
  • Changes that trigger height or volume thresholds must be carefully considered, as in principle the standard should be applied to the full risk area

Full Report

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The Full Report below has been submitted to CROSS and describes the reporter’s experience. The text has been edited for clarity and to ensure anonymity and confidentiality by removing any identifiable details. If you would like to know more about our secure reporting process or submit a report yourself, please visit the reporting to CROSS-UK page.


This report discusses the perceived exploitation of a common fire safety argument: the existing condition. The reporters highlight the question to be asked; “Is it truly no worse than the existing condition?”  

The reporters have witnessed, through their professional capacity, a trend in which buildings are being substantially altered in their occupancy and can also be physically changed by an increase in building height or footprint, but any consideration of certain fire safety provisions is omitted on the “tenuous” basis that the altered design is not "worsening" the existing condition.

The foundation of this argument results from clauses provided in Paragraph (3) of Regulation 4 of the Building Regulations 2010, and from another clause in Approved Document B (ADB), where it is stated: “For work on an existing building that did not comply with the applicable requirements of the Building Regulations:

  • the work itself must comply with the applicable requirements of the Building Regulations, and
  • the building must not be more unsatisfactory in relation to the requirements than before the work was carried out”.  

Examples of this practice in recent years include the extension of residential buildings with additional storeys and the increase in the building footprint with the addition of more apartments per floor. With these examples, if the buildings were to be designed under contemporary guidance, then, depending on the building height, it would be expected to include fire safety provisions such as suppression systems, firefighting shafts and lifts, automatic smoke control within the corridor or lobby, or more. However, the reporters have witnessed situations where the fire strategy for altered buildings omits the inclusion of certain fire safety provisions on the basis that they were not present in the existing building. Variations of this have been observed whereby the building extension incorporates the provisions expected by contemporary guidance, but the existing building portion remains largely or entirely unaltered.

some of these designs are gaining Building Regulations approval and are being built and occupied

While it may be anticipated that such practices are rectified during quality assurance procedures and third-party reviews, it does appear in the reporters’ anecdotal experience that some of these designs are gaining Building Regulations approval and are being built and occupied, with limited concerns highlighted by the authorities having jurisdiction during the approval’s process.

has the potential to substantially alter the risk profile of a building

The reporters acknowledge the practical difficulties and complexities that arise from making alterations to existing buildings, particularly with the retrofitting of fire safety systems. However, it is their view that in many instances the argument of "no worse than existing" is being negligently exploited to facilitate inadequate design. In the examples provided above, the addition of more storeys or more apartments per floor has the potential to substantially alter the risk profile of a building. The addition of more apartments increases the likelihood of a fire occurring, as well as the number of occupants located within the building. It thus follows that without any appropriate consideration of the collective fire safety measures, the risk associated with fire hazards is increased. These alterations also have the potential to impact firefighting operations within the building, placing additional pressure on the fire service when fighting the fire and carrying out rescue operations.  

Given the above, it is the reporters’ view that, unless the existing building and new alterations are demonstrably independent, i.e., the 'existing' portions of the building do not interact with the 'new' portions, then it cannot be reasonably argued that alterations are not worsening the existing condition. However, this independence is rarely the case in practice and, in most situations, the existing building and the building extension form a holistic system of many interacting components. In this system, occupants may share common escape routes, the fire service may utilise these common escape routes to access the building, new storeys likely share the same structure as existing storeys, and so on. Ultimately, the provisions (or lack thereof) within one part of the building have the potential to substantially impact the performance of another part of the building. Under these circumstances, it is difficult to argue that the existing condition is not worsened, and the omission of any provisions expected under contemporary guidance is reasonable. Such an argument could be, at the least, based on clear evidence that the design collectively achieves an adequate level of safety, e.g., by a quantitative assessment which considers both the existing and new portions of the building (along with any potential interactions).

not a means of avoiding responsibility for demonstrating adequate design

The reporters state that there are individuals within the fire safety industry that would propose that the argument of "no worse than existing" needs to be revisited or abandoned entirely, and the industry needs to do more to improve the safety of existing buildings when offered with an opportunity to do so; a building refurbishment or extension presents one such opportunity. This is a reasonable and well-intentioned suggestion, although it will inevitably come with complications and unforeseen consequences if its implementation is not carefully considered. Despite that, it appears that before the industry can ever reach that point of consideration, a minority of engineers first need to be convinced that "no worse than existing" is not a loophole to be exploited, it is not a way of circumventing difficult discussions, and it is not a means of avoiding responsibility for demonstrating adequate design.

Expert Panel Comments

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Expert Panels comment on the reports we receive. They use their experience to help you understand what can be learned from the reports. If you would like to know more, please visit the CROSS-UK Expert Panels page.

The reporters are right to raise and discuss this issue. Cases where a fire safety measure is not included with 'non-worsening' cited as the reason by the designer, engineer, or building control body are a recurring experience within the panel.

Part of the reason why this clause exists, is that building regulations are not retrospective. Engineers do not revisit every building to conduct upgrades every time the regulations change. This way, occupants are not made to upgrade everything about their existing buildings when any kind of work occurs; for example, replacing windows shouldn’t necessarily trigger a need for adding structural components.

If the building works includes extending the building, particularly if that includes making it higher, then the designers would have to make sure that the new areas fully comply with current standards and that the works won't make things worse for the existing areas. It's really the responsibility of the designers to make sure that happens and for Building Control to check that this is done.

the new works must fully comply

Where this is increasingly becoming misused is in deciding that things are not 'worse'. The new works must fully comply, but some people may think this means the new works can be no 'worse' than the existing. This is clearly not the case.

What is less clear is when the work has less direct impact on the existing premises. For example, in a case of adding floors to a building, to an extent that it changes classes (disproportionate collapse), then it should be seriously considered if the whole building should be brought up to current standard because the existing building supports the extension. In principle, alterations which change the fire risk profile affect the whole building.

alterations which change the fire risk profile affect the whole building

Another common example of an issue is when a vertical extension triggers the need for sprinklers due to the new height, because it now reaches the threshold for a suppression system; then in principle the whole building needs the upgrade. In terms of guidance, BS 9251 (domestic sprinklers) states, when installing sprinklers in a building, that ‘all parts of the premises should be sprinklered’. This is one solution that would ensure “that the standard of fire protection for the occupants of the new accommodation is as would be provided for a new building under the approved document”, a clarification found below, in the cited frequently asked questions on ADB.

The non-worsening clause is also commonly referred to when some designers assess the access and water supplies for the Fire and Rescue Service (FRS), and the experience of the panel is that whatever is in existence is accepted as being adequate.

The difficulties of practically achieving the holistic solution are often cited as a reason not to do things, and should be evaluated on a case-by-case basis, but ultimately some projects should not be going ahead if it is not practicable, hence unsafe, to complete them properly.

The FRS has very limited options via the Regulatory Reform (Fire Safety) Order (FSO), as it does not provide a route to enforce retrospectively requirements of the Building Regulations, although the FSO does impose an expectation of continuous improvement and adaptation to new technologies. The latter is limited, again, in respect to a risk-based life safety assessment.

Examples in Approved Document B

Examples provided in the Approved Document B: Fire safety - frequently asked questions website can be relevant in this discussion. These are reproduced below, namely questions 9 and 20:

9. If an existing single storey shop is extended so that it exceeds the maximum 2000m2 compartment size, is it necessary to install a sprinkler system?

Regulation 4 (1) of the Building Regulations 2010 states that “building work” should comply with the applicable requirements contained in Schedule 1. Regulation 4(3) then goes on to state that after the work is completed the building as a whole should comply with the applicable requirements of Schedule 1 or, where the building did not previously comply with any such requirement, is no more unsatisfactory in relation to that requirement than before the work was carried out.

Where an existing shop is extended such that the final floor area is greater than 2000m2 (whether it exceeded this value previously or not) then the building as a whole may be less satisfactory in relation to Schedule 1 requirement B3(3) than before the work was carried out. Therefore, the building would have to be either subdivided to limit the compartment size, fitted with sprinklers or some other solution would be necessary in order to satisfy regulation 4(3) in relation to requirement B3. Regulation 4(3) must be judged against the requirements set out in Schedule 1 rather than the Approved Document. B3(3) requires sub-division of the building “to an extent appropriate” to its size and intended use and it may be that some buildings will still comply with requirement B3(3) by virtue of its intended use even though they have been extended without further compartmentation.

And question:

20. I am undertaking work on an existing building which is below 11m, and adding a new floor which will exceed 11m in height, do I need to sprinkler the whole building or just the new floor?

Each case must be considered on its own merits, but it is likely that where additional storeys are added to an existing building, some work on the original part of the building will be necessary.

Applicants and building control bodies are reminded of the need to consider these new provisions sprinklers in relation to extensions as required by Regulation 4(1). New accommodation, formed by building work, should meet the relevant requirements having considered the guidance in the approved document. This means ensuring that the standard of fire protection for the occupants of the new accommodation is as would be provided for a new building under the approved document. In the majority of cases, therefore, sprinkler protection will be necessary in any newly formed accommodation that falls above the new 11m trigger height.

It may also be necessary to consider additional protection for the existing parts of the building where needed to ensure that the extension is compliant with the applicable requirements of Schedule 1. Equally, it will be necessary to satisfy regulation 4(3) by ensuring that the level of fire protection in the building as a whole is made no worse.

There may also be situations where the risk assessment for the building (provided under the Fire Safety Order) requires further work to be done. Regardless of the minimum requirements of the regulations there is, of course, merit in providing additional protection throughout the building.

Further advice can be found in the following circular letter.

One for debate

Finally, as for the opinion that the approach should be abandoned entirely, this is a matter of debate. Any change in law can always have unintended consequences, in this case for any people doing very minor works. Until this debate is resolved, better enforcement of building regulations in all building types is needed. To that end, any further clarification or guidance (by Government) on how this regulation should be approached, because it being open to interpretation is recognised as the crux of the issue, is most welcome.

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