Changing the use of a building requires compliance with Building Regulations specific to its new purpose, but the legal trigger is just the beginning
John Gardner, national specification manager at fire stopping specialist FSi Promat, has seen first-hand how the complexity of passive fire protection in these projects is often underestimated.
“The assumption in many cases is that existing fire protection can carry over,” he says.
“In reality, a change of use almost always means starting the fire safety assessment from scratch.”
The legal position is clear. As a House of Commons briefing on construction regulation sets out: “Existing buildings generally do not need to be retrofitted to comply with new legislation or building regulations, as regulations are typically not retrospective.
“However, compliance is mandatory when undertaking renovations, extensions, material alterations or changes of use.”
A change of use project therefore triggers a legal duty to revisit a building’s fire safety requirements in full. Understanding that legal position is the first step toward compliance.
The regulations
The Building Regulations 2010 set the construction standards, designed to protect
the safety of building occupants. Under Regulation 5, a material change of use covers a broad range of scenarios – from converting a building into a residential dwelling or adapting to accommodate flats to changes involving hotels, shops or previously exempt structures.
Generally, each of these requires planning permission, unless covered by permitted development rights (PDR), but Building Regulations apply in either case. Under Regulation 6, the building must also meet specific requirements covering ventilation, energy, hygiene and fire safety.
Fire compartmentation
Fire stopping is a key element of passive fire protection, involving the sealing of openings to prevent fire from spreading through a building. By creating fire-resistant cells or barriers, it contains the spread of fire, heat and smoke within defined zones. Crucially, this gives occupants time to escape and enables the fire services to operate safely.
Compartmentation is therefore a vital consideration in all buildings. However, specifying fire stopping systems, such as cavity barriers, is not always straightforward. In change-of-use projects, existing passive Fire protection cannot be assumed to meet the requirements of the new use. It is imperative, therefore, that compliant passive fire protection is built into designs from the outset.
A common driver of change-of-use projects today is the conversion of underused office space, reflecting the shift to hybrid working. Converting offices to residential use moves a building from Class E to Class C3, requiring compliance with Approved Document B (Volume 1: Dwellings) – requirements that differ significantly from those for commercial buildings.
Many such offices were originally open plan; converting them into flats and shared spaces means compartmentation becomes essential to contain fire spread between areas.
Ageing and non-standard structures present a significant challenge when changing their primary use. Where passive fire protection is already in place, contractors cannot always be certain of the materials involved, the solution originally used or whether it meets current standards.
“This is where we often see things go wrong,” says Gardner. “People specify a solution without fully understanding what’s beneath it and that’s a risk no passive fire protection system can compensate for.”
The introduction of the Golden Thread – the requirement to maintain and share a complete record of a building’s materials and systems throughout its lifecycle – should reduce this uncertainty over time.
For existing buildings, however, the gap in knowledge remains, and having a clear understanding of the substrate required is essential before specifying any fire stopping solution.
Working in occupied buildings presents its own difficulties, particularly where access prevents working on both sides of a wall. Single-sided, tested and certified solutions can overcome this challenge, avoiding the need to temporarily decant residents or close offices during refurbishment.
Service penetrations
In change-of-use projects where the passive fire protection has been upgraded (or even introduced), accurate use of fire stopping components is necessary to reinstate compartmentation where there are any cracks, gaps or service penetrations (for both pipework and cabling). All fire stopping products and systems should be third-party certified and tested using the relevant standards.
For effective protection, a holistic approach is required. In addition to the walls and ceilings, any element that forms part of that compartment line, such as doors, fire stopping or steelwork encasements, must maintain the performance of the element as a whole.
Penetration seals need to be tested and certified for the specific service types. These also need to be spaced correctly to meet requirements – if they are too close together, or too close to perimeters, it can compromise performance. Ensuring proper gaps between multiple services allows for effective sealing. This is a consideration for upgrading around existing pipework and also for any new cabling or pipework.
Factoring in deflection and movement
It is essential that all gaps are sealed where compartmentation is in place and this includes in deflection heads to accommodate movement and where fire stopping is required on walls, ceilings and floors to close gaps.
Where a building is subject to deflective movement, it is important this is accounted for in passive fire protection, building in the flexibility to move with the building to prevent cracks forming and destroying compartmentation.
It is important that the movement built into the wall is also accommodated in any fire stopping used. Where fire stopping is used to seal the join between a wall and ceiling or floor, it is vital that it supports the required flexibility.
To this end, a flexible fire stopping system should be used in line with EN1366-3 for penetration seals and/or EN1366-4 for linear joints. Any seal used must accommodate the movement or it will risk cracking under the forces of sheer, extension and compression as a result of loading, settlement or wind load.
Complex interface challenges
In change-of-use projects, often there are difficulties due to ageing, incompatible or non-standard structures. This is a particular problem in existing structures as there is an element of the unknown in what materials have been used.
Thanks to the introduction of building information storage and sharing practices, known as the Golden Thread, this problem should be phased out moving forward. But it is important to have absolute clarity on the substrate to ensure the correct testing is in place.
Another major challenge is working in a building that is already occupied and working in buildings where access is an issue and it is impossible to work on both sides of a wall. Tested and certified single-sided solutions from FSi Promat offer a way to solve that challenge in retrofit projects and can also be used to prevent installation requiring temporary rehoming or office closures.
How FSi Promat can help
The regulatory landscape for fire safety continues to evolve but the fundamental principle does not. Occupants must be protected, and passive fire protection has to be specified correctly from the outset. In change-of-use projects, that responsibility falls on every member of the project team, from architect to principal designer to contractor.
“Getting fire stopping right in these projects isn’t just about compliance,” says Gardner.
“It’s about making sure that if something goes wrong, the building does what it’s supposed to do and its occupants can get out safely. That has to be the standard every time.”
FSi Promat offers technical specification support for fire stopping across a wide range of projects, including bespoke specification packs, tested solution configurations, compliance data and classification reports. Products are tested to EN standards and third-party certified.
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