Fire evidence for a change of use to flats in a block

Change of use flats fire evidence divides into two very different cases, and the first thing to establish is which one you are in. If the building will contain two or more dwellings and has a storey at least 18 m above ground level, or seven or more storeys, a Fire Statement on the published form is required with the planning application and the Health and Safety Executive is consulted at Planning Gateway One. Below that threshold there is no statutory Fire Statement requirement outside London, and yet fire safety is still a material consideration, and the evidence you supply decides how much of the design risk you are carrying into the Building Regulations application.

Whether your building is a relevant building at all

The 18 m or seven storey test comes from the fire statement provisions in the Development Management Procedure Order 2015, which sit alongside the wider Building Safety Act 2022 framework. Measure it properly: the height is to the floor surface of the top storey, excluding roof plant areas, and the storey count includes any storey that is not wholly below ground.

A four storey Victorian commercial building becoming eight flats is not a relevant building. A conversion of a 1960s office block of eight storeys is, even if the office use never triggered anything.

London is the exception worth knowing. London Plan Policy D12 requires fire safety to be addressed in all development proposals and requires major development to be accompanied by a fire statement, regardless of building height, so a London conversion of ten or more units needs one whether or not the 18 m test is met. A Fire Statement is a document that has to be prepared by someone with the necessary fire engineering competence, because it is required under the Building Safety Act framework and Article 9A of the 2015 Order, and an AI-assisted draft is a starting point for that professional rather than a substitute for them.

Establishing what compartmentation already exists

Everything downstream depends on this, and almost nobody budgets for it properly.

You need to know what the existing floors and walls actually are, not what the original drawings said. That means opening up: lifting a section of floor, cutting an inspection hole in a ceiling, checking whether the party wall continues through the roof void, and establishing whether service risers were ever fire stopped. In buildings converted once already, the usual finding is a compartment line that stops at a suspended ceiling.

Record what you find with photographs, locations marked on a plan, and an assessment of the notional fire resistance achieved. For flats, Approved Document B expects compartment floors and walls between dwellings and a protected escape route, and in an existing building the gap between what exists and what is needed is the whole of your construction cost.

Structural condition and fire resistance are usually surveyed together, because both depend on opening up the same places. Where the structure is being retained rather than replaced, the appraisal has its own planning consequences, and our note on structural appraisal of a building proposed for retention sets out what the authority looks for.

Means of escape in a building not designed for dwellings

An office escapes by simultaneous evacuation. A block of flats, in the normal English approach, relies on each dwelling being a fire compartment so that residents elsewhere can stay put, with a protected stair for those who need to leave.

That difference drives the hard constraints.

• Travel distance from a flat entrance door to the stair, where escape is in one direction only, is short, and corridors in converted buildings are frequently longer than the limit allows
• A single stair needs protection at every level, and a lobby or ventilated corridor arrangement between the flats and the stair
• Smoke control, whether an automatic opening vent at the head of the stair or a mechanical system, has to be designed and has to go somewhere, and in a conservation area a new roof vent is a visual question as well as a technical one
• Sprinklers are expected in new residential buildings above 11 m, which pulls in a water supply, a tank, a pump room and a maintenance regime
• Flat entrance doors need a fire and smoke rated specification with self closing devices, which is straightforward in new work and contentious where the doors are original joinery in a listed building

Where the geometry does not work, the answer is usually either fewer units on the upper floors, a second stair carved out of lettable space, or a fire engineered solution. The third option is not a shortcut. A Fire Safety Strategy to BS 9991 or BS 9999 is a fire engineering document and the law treats it as one, so a competent fire engineer has to author it.

Mixed commercial and residential risk in one structure

Retaining a shop, restaurant or gym at ground floor while putting flats above is the common conversion, and it is the one that produces the most difficult fire case.

Four points recur. The residential and commercial parts need separating as distinct compartments, with the floor between them and any shared structure detailed accordingly. The residential escape route must not pass through the commercial unit or its service areas, which often means forming a new separate entrance and a dedicated stair core. A commercial kitchen below flats raises the fire load and the ventilation duct becomes a route for fire spread between compartments. And the commercial occupier has duties under the Regulatory Reform (Fire Safety) Order 2005 while the residential common parts fall under the Fire Safety (England) Regulations 2022, so the management arrangements have to be set out, not assumed.

Say in the application who will be responsible for the common parts and the fire door inspection regime after completion. Authorities increasingly ask, and a management structure sketched at planning stage costs less than one retrofitted at handover.

Works that need a separate consent

Planning permission is one of four or five things you need, and the sequence matters.

1. A full plans Building Regulations application, because a material change of use brings the relevant requirements of Part B into play for the whole building rather than the altered parts alone.
2. Where the building is 18 m or seven storeys and residential, the Building Safety Regulator gateways apply to the construction phase as well as the planning stage.
3. Listed building consent for any intervention in a listed building, including upgrading doors and inserting compartment walls.
4. Party wall notices under the Party Wall etc. Act 1996 where compartment work touches a shared wall. That Act is not a planning matter and PlanScope does not produce party wall documents, but it sits on the critical path.
5. A fire service access and water supply check with the local fire and rescue service, which is a consultee in practice even where it is not a statutory one.

What the planning submission should contain

Where no Fire Statement is required, submit a short fire safety note anyway. Four or five pages, written by someone competent, covering the existing construction and what the opening up found, the proposed compartmentation and escape strategy in outline, the evacuation strategy and whether it is stay put or simultaneous, fire service access and hydrant positions, external wall construction and whether any combustible material is present, and the smoke control principle with any external vents shown on the elevations.

The last point is the one that affects the planning drawings. Vents, dry riser inlet boxes, sprinkler tank enclosures and a new stair core all appear on elevations and in the roofscape, and an officer who sees them for the first time at Building Regulations stage will ask whether the permission covers them. It usually does not, and you are then applying under section 96A or section 73 to vary the approved plans.

A Structural Survey commonly carries the opening up findings that the fire note relies on, which is why commissioning both at once saves a second round of scaffolding and access.

Where the building cannot be made to work

Some buildings should be refused by you rather than by the council. The signs are consistent: a single stair serving a deep floorplate with corridors well over the single direction travel limit, no route for a second stair that leaves viable units, a basement commercial use with no independent escape, external wall build ups of unknown composition on a building near the 18 m threshold, and a party wall shared with a building you have no access to.

Walk away or reduce the scheme. The alternative is a permission you cannot discharge the Building Regulations against, which is worth less than no permission at all.

If you are working out which supporting documents a conversion of this type needs, enter the postcode on PlanScope and work through the site constraints first.

This is general guidance, not legal advice, so check the position with your local planning authority or a qualified professional before relying on it. For specialist technical reports, qualified professional input may be required. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.