Key takeaways
- Most conversions are a material change of use, which brings the fire safety requirements into play
- The existing building has to meet them, not just the new partitions
- A fire strategy shows building control how the converted building complies
- In Wales, new homes created by conversion usually need sprinklers
- Start the strategy before the layout is fixed: stairs and compartments drive the plan
What counts as a change of use
The Building Regulations list the changes of use that count as "material". In both England and Wales they include a building being used as a dwelling where it was not before, a building containing a flat where it did not before, and a building becoming a house in multiple occupation, a hotel or boarding house, or an institution such as a care home.
Typical projects we see:
- Offices or shops to flats, often above a ground-floor commercial unit
- A house to an HMO, or a house split into self-contained flats
- A pub, chapel or industrial unit to residential
- A large house to a care home or supported living
- Adding a storey or a loft conversion that changes the escape route from upper floors
Why the existing building matters
On a material change of use, the regulations require the building to meet certain requirements as a whole, including the main fire safety requirements of Part B: means of warning and escape, internal fire spread, structure, and firefighting access. In practice that means building control will look at the original floors, walls, stairs and doors, not only at the new work.
That is where conversions catch people out. Common problems we find:
- Timber floors between the new flats that do not give the fire resistance needed between dwellings
- A single staircase that becomes the only escape route for several flats
- Service risers, ceiling voids and old chimneys that bypass the new compartment walls
- Inner rooms, where a bedroom can only be reached through a living room or kitchen
- Existing doors onto the stair that are not fire doors, or have been altered
What the fire strategy covers
For a conversion, the fire strategy sets out how the building will be made safe in its new use and which guidance it follows. It normally covers:
- The evacuation strategy: stay put for well-compartmented flats, or simultaneous evacuation for most HMOs
- Means of escape: travel distances, the protected stair, inner rooms and escape windows
- Compartmentation: fire resistance between flats and to the stair, and how existing floors will be upgraded
- Detection and alarm: the grade and category of system for the new use
- Sprinklers or other suppression where required or used to justify a departure
- Firefighting access: how the fire service reaches the building and the stair
- Mixed use: separation between flats and any commercial space below
Where the existing building cannot meet the guidance exactly, for example a travel distance that is slightly too long, the strategy sets out the compensating measures and the justification, so building control can assess it.
England and Wales: what is different
In England
Designs follow Approved Document B or a British Standard such as BS 9991. Some office-to-residential conversions are permitted development under planning rules, but they still need Building Regulations approval. Relevant buildings of 18 metres or more need a fire statement at planning stage, and higher-risk buildings go through the Building Safety Regulator.
In Wales
Designs follow Approved Document B (Wales). Under the Domestic Fire Safety (Wales) Measure 2011, new homes created by conversion, including flats and HMOs, generally need an automatic fire suppression system, usually residential sprinklers to BS 9251. Water supply and tank space need planning from the start.
When to bring in the fire strategy
As early as possible, ideally while the architect is still working out the layout. The number and position of stairs, where the compartment walls run and whether sprinklers are needed all shape the floor plan and the budget. Leaving the fire strategy until the building control application often means redesign, extra fire-resisting work or a scheme that loses a unit.
We write fire strategies for conversions across Wales and England. Send us your drawings and tell us where the project is in the design programme, and we will confirm the scope, the guidance we will design to and a fixed price.