Office-to-residential conversions: a fire safety checklist

Why conversions are different

An office is designed for occupants who are awake, familiar with the building and evacuate together. Flats are designed around people who may be asleep, behind their own front doors, and who may be told to stay put while a fire is dealt with. That only works if each flat is a fire-resisting compartment and the common escape routes are protected from smoke.

Many conversions – particularly early permitted development schemes – have struggled with this. Slough, Reading and other Thames Valley towns have seen a lot of office-to-residential conversions, and so has outer London.

The planning stage

• Class MA prior approval: where the conversion creates a relevant building (18m+ or 7+ storeys with two or more dwellings), the Building Safety Regulator is a statutory consultee and floor plans are needed for each storey changing to residential use.
• Full planning applications for relevant buildings need a Fire Statement Form, and London's Policy D12 may require a fire statement for major schemes.
• Upward extensions under Class A or AA need a fire safety report on the external walls.

See Planning Gateway One.

The building regulations stage

A material change of use to flats must meet the fire safety requirements for the new use. For higher-risk buildings, the building control application goes to the regulator at Gateway 2. Key design checks:

1. Means of escape – travel distances in common corridors, protected lobbies, single or multiple stairs, and smoke ventilation of corridors
2. Compartmentation – every flat separated from its neighbours and the common parts, with compartment floors and walls continuing above ceilings
3. Flat entrance doors – self-closing fire doors with smoke seals
4. Detection and alarm – suitable detection within each flat, and a strategy for the common parts that fits the evacuation approach
5. Sprinklers – Approved Document B recommends sprinklers in blocks of flats with a top storey more than 11m above ground; check the position for your scheme early
6. External walls – combustibility of existing and new cladding and insulation; the ban on combustible materials can apply to relevant buildings of 18m and over
7. Fire service access – firefighting shafts, dry risers and vehicle access for taller buildings
8. Staircases – check early whether the second staircase requirement affects your scheme

For managing agents running an existing conversion

Converted buildings often lack the design information you need. Check:

• Is there a fire strategy that reflects the conversion, not the original office? If not, see retrospective fire strategies.
• Has compartmentation been checked above ceilings and in risers? See compartmentation surveys.
• Is the evacuation strategy – stay put or simultaneous – supported by the construction and alarm system?
• Are the external walls assessed? Some conversions were re-clad. See what an FRAEW is.
• Does the fire risk assessment go beyond a Type 1, where needed? See FRA types 1–4.

Typical problems in converted buildings

• Corridor walls stopping at the suspended ceiling, leaving an open void between flats and the escape route
• Unsealed service penetrations where new pipes and cables were added for the flats
• Original office smoke ventilation that isn't suitable for residential corridors
• Flat entrance doors without self-closers or proper fire rating
• Inner rooms – bedrooms that can only be reached through a living room or kitchen
• Mixed uses – retained commercial floors without adequate separation from the flats
• Missing information – no record of how the conversion was assessed

Most of these can be fixed once they're found. The first step is a clear picture of how the building is meant to work.

Our fire strategy reports cover change of use from planning to handover, and we work across Slough, Reading, London and the UK.

Sources

• Planning Portal – Planning Gateway One and prior approval applications
• GOV.UK – Approved Document B: new updates to support enhanced fire safety

This guide is general information based on the law and guidance in England as at 8 November 2026. It isn't legal advice – for advice on a specific building, get in touch.