What we learned in developing an HRB safety case process

To compile a safety case and demonstrate the ongoing safety of higher-risk residential buildings, building owners, maintenance staff and operators must understand the condition of their assets and the associated hazards.

In doing this, they must recognise the wealth of knowledge that residents and commercial tenants can provide: the safety of building occupants is everyone's business.

Under the 2022 Act, all new and existing HRBs – currently defined as buildings taller than 18m or seven storeys or more that contain at least two residential units – must be registered with the new Building Safety Regulator (BSR) to be lawfully occupied.

The legislation also requires that dutyholders prepare and maintain a safety case for each HRB, which is submitted to the BSR as part of the building assessment certification process. This safety case must demonstrate that the principal accountable person has taken 'all reasonable steps' to manage building safety risk; that is, fire safety and structural safety risks.

Therefore, Arup consultants have carried out internal research to develop a tailored HRB safety case methodology specifically for residential buildings. The methodology is based on the firm's extensive experience of preparing safety cases in high-risk industries including rail, nuclear, hydrogen, oil and gas.

These each have specific regulations and standards for identifying and analysing safety risks, which have been developed over decades and are informed by several major incidents such as the 1999 Ladbroke Grove rail crash and the 2010 Deepwater Horizon oil spill.

However, not all the requirements for these industries are proportionate for residential buildings.

In order to understand the impact of the new legislation on key HRB stakeholders, Arup hosted a workshop under the Chatham House rule with selected residential developers, landlords, housing associations and residents.

As part of this, each stakeholder was asked what they know, how they know it, and what to do with a safety case once it is prepared, as well as assessing what residents need.

The workshop explored the collection of building information, the wealth of knowledge that residents can provide, and how the sector must adapt to manage the ongoing requirements of the safety case once it has been prepared.

In England in particular, the structure of ownership and responsibilities for buildings can be complicated, particularly for mixed-use buildings with a combination of residential and commercial units. An HRB may, for instance, be part of a larger building, with residential apartments on the top floors of a mixed-use office and retail development.

Hazards relating to areas outside the formal HRB boundary must also be considered, and therefore stakeholders who are not within the HRB itself, such as Responsible Persons of other demises, may still need to be engaged as part of the safety case process.

During the discovery stage, gathering stakeholders around a table for a HAZID workshop, is a powerful way of putting a face to the names responsible for managing safety in a building – reinforcing the idea that protecting occupants is everyone's business.

The safety case process should support the partnership between the principal accountable person, other accountable persons, management, tenants and residents. HAZID workshops can promote such cooperation between dutyholders.

Conversely, the structural or fire safety experience of HRB stakeholders can vary significantly. Investing time to take them through the whole process and encourage engagement and participation is key to understanding and managing risk.

For many buildings, the discovery stage also identifies safety risks that the principal accountable person may not have known about, or which were not picked up during safety assessments.

There is often limited or inaccurate information about existing buildings – and even where it is accurate it may be spread across different stakeholders, each with their own operational procedures and information management systems.

Furthermore, Arup has encountered buildings where the mitigation measures to reduce fire spread or structural failure are not operating as intended or have been incorrectly installed or modified.

There will be instances where it is more appropriate to acknowledge uncertainty about safety measures that are hard to inspect and assure. It may be better to confirm existing critical safety systems that can be readily inspected or tested are operating correctly, and adding new systems to compensate for residual uncertainty.

With this in mind, the Institution of Structural Engineers has recently published a compendium of common defects with different types of building, to which Arup staff have contributed.

Expert judgement will be important to determine where investment has the greatest impact on risk management. Time and money can be spent searching historic records that may be incorrect, or carrying out destructive surveys or exhaustive analysis that may not make a substantive difference in the assessment of risk.

The evaluation stage is used to appraise, in a holistic way, the options for verification, remediation, upgrade or addition of safety control measures, and any proportionate steps reasonable to demonstrate building safety.

Preparing safety cases, with HAZID workshops for more complex buildings, provides an opportunity to bring together all relevant stakeholders for a building, enabling positive engagement and deeper understanding of its safety, though this process does take time.

Arup's proportionate safety case process seeks to build a shared appreciation of risk, and we hope our work can help inform the development of pathways and benchmarks for the wider industry, making homes across the country safer.