When the Use of a Building Changes, the Fire Risk Changes Too

Buildings and their use evolve over time, often without anyone formally acknowledging that something fundamental has changed. A warehouse begins storing different materials. A retail unit starts holding bulk stock on site. A commercial building takes on a mixed role, part storage, part sales, part logistics hub. From the outside, very little looks different. Inside, however, the fire risk has altered.

Fire safety is always based on assumptions. Assumptions about what is present, how it is handled, how often it moves, and how people interact with the space. When those assumptions no longer reflect reality, the measures built around them lose their relevance. The risk does not suddenly appear. It has usually been there for some time, waiting for the right conditions to expose it.

Why changes in use are often missed

Changes in use are not always the result of a formal decision. They are often driven by pressure. Pressure on space, pressure on costs, pressure to adapt quickly. Storage areas expand. Different stock is introduced. Temporary arrangements become normal practice. Over time, the building is being used in a way that would not have been anticipated when its fire safety arrangements were first considered. This is especially common in industrial and commercial settings, where flexibility is seen as a strength. What is less often recognised is that flexibility brings responsibility. When a building takes on a new role, even partially, the fire risk assessment that once felt suitable can become outdated.

Southall Warehouse Fire - November 2025

In November 2025, a major fire broke out at a warehouse in Southall, west London. The incident was significant enough to be declared a major emergency, with a large scale response from the London Fire Brigade and the evacuation of nearby properties, including schools and residential buildings. Thick smoke was visible for miles, and emergency services raised concerns about the nature of materials stored inside the warehouse.

Early reporting suggested that fireworks or other highly combustible items may have been present, dramatically increasing the severity of the fire compared to what would normally be expected in a standard commercial warehouse. The building was not simply behaving as a neutral storage space. Its use, and the materials it contained, had altered the way the fire developed and the level of risk it posed to the surrounding area.

This case is an example that fire risk is not defined by building type alone. A warehouse storing low risk goods behaves very differently from one holding hazardous or highly combustible stock. If that change is not properly recognised and assessed, the consequences can extend far beyond the premises itself. The Southall fire was widely reported in the national press, highlighting the scale of the response and the disruption caused to the local community.

What this tells us about commercial fire risk

The lesson from Southall is not about blame. It is about awareness. Commercial and industrial buildings often change faster than their paperwork. New stock lines are introduced. Storage densities increase. Processes evolve. Each of these changes can affect ignition likelihood, fire load, smoke production and fire spread. A fire risk assessment that does not reflect those realities becomes a historical document rather than a live management tool. It may still exist. It may still be filed away. But it no longer describes the building as it is actually used. If the risk changes, you must conduct a new fire risk assessment, something that Fletcher Risk can help you with.

Change does not have to be dramatic to matter

One of the most dangerous assumptions in fire safety is that only major changes require review. In reality, it is often the incremental changes that carry the greatest risk. A different supplier. A new product line. A shift from distribution to longer term storage. None of these may feel significant on their own. Together, they can transform the fire behaviour of a space. In places we visit in our home city of Chester and across the wider region, many commercial buildings occupy older stock that has been adapted repeatedly over time. These buildings are resilient, but they rely on careful management. Recognising when use has shifted is part of that responsibility.

Seeing the building as it is now

Reviewing fire risk after a change of use is not about starting from scratch. It is about seeing the building clearly again. Understanding what is stored, how it is moved, who is present, and how a fire would realistically develop if one were to start. This clarity allows proportionate decisions to be made, focusing effort where it actually reduces risk rather than where it simply feels reassuring. When this process is done well, it often brings relief rather than alarm. Uncertainty is replaced with understanding. Fire safety becomes easier to manage because it aligns with reality.

What you should do next

If the way your building is used has changed, whether through storage, processes or occupancy, it is worth considering whether your fire risk assessment still reflects that reality. Arranging a new assessment after a change of use is not an admission that something is wrong. It is a sensible step to ensure that assumptions remain valid and that fire safety arrangements remain proportionate and defensible. A short conversation is often enough to establish whether a review is needed. Taking that step early helps ensure that change does not become risk. Please contact us for more information.

Disclaimer

This article is provided for general information only and does not constitute legal advice. Fire safety duties and appropriate control measures depend on the specific premises, use, materials stored, management arrangements and findings of a suitable and sufficient fire risk assessment. If you require advice on your circumstances, you should seek competent professional support.

Tim Fletcher29 December 2025