Fire statements for the conversion of an existing block

A fire statement for an existing building conversion is a harder document than one for a new build, and the reason is simple: on a new build you know what you are specifying, and on a conversion you are describing a building whose construction nobody has seen since it was finished. The Building Safety Regulator will read your statement knowing that, and the submissions that work are the ones that say plainly what has been surveyed, what has been assumed and what will be opened up before the next gateway.

The submissions that fail are the ones that describe the existing block with the same confidence as a new design.

Whether a conversion engages the duty

The Gateway One consultation duty in Article 9A of the Town and Country Planning (Development Management Procedure) (England) Order 2015 covers development involving a relevant building, which includes work to an existing one. A relevant building contains two or more dwellings or educational accommodation and has at least seven storeys or is at least 18 m high.

Three conversion scenarios engage it, and one of them surprises people.

An existing residential block above the threshold being refurbished or extended engages the duty straightforwardly. A building that is pushed over the threshold by the proposal, typically by added storeys, engages it from the moment the proposal is drawn. And an existing non-residential building above the threshold, such as an office block, being converted to flats engages the duty even though it contains no dwellings today, because the relevant building is the one that will exist.

That third case is the one that catches office-to-residential schemes. Measure the height from existing ground level to the floor surface of the proposed top storey, excluding storeys that will consist exclusively of plant, and do it before the design is fixed.

Where a conversion proceeds by prior approval rather than by planning application, the consultation duty operates differently and the position should be confirmed with the authority at the outset. The building control gateways under the Building Safety Act 2022 apply either way, so nothing is avoided by the route chosen.

Surveying what the building actually is

Record drawings are a starting point and not evidence. Buildings of the relevant era were altered, re-serviced, re-clad and sub-divided, often without a trace in the building control file.

The survey questions that the fire statement depends on are these. What is the structural frame and what is its fire protection. Where is the compartmentation and is it continuous, particularly at floor junctions and around risers. How are services penetrating compartment walls and floors sealed. What is the stair enclosure built from and how is it ventilated. What is the external wall build-up, layer by layer. Where are the cavity barriers, if any.

None of those can be answered by inspection from a corridor. They need opening up, which means a programme of intrusive investigation, access agreements with existing occupiers if the building is tenanted, and making good. Budget it and programme it, because it takes weeks and it frequently changes the scheme.

A structural appraisal runs alongside the fire survey and uses much of the same access. Commission them together. The structural survey and the fire investigation both want the same ceilings down, and doing them in sequence doubles the disruption for no benefit.

Constraints the existing structure imposes

The existing building limits the fire strategy in ways a new build does not, and the statement should name the constraints rather than designing around them silently.

Floor-to-floor height constrains the depth available for services, which constrains how smoke control ductwork can be routed. Existing core positions constrain travel distances, and a core that served an open-plan office at 20 m centres may not serve a residential layout at all. Structural capacity constrains what can be added. Existing risers may be too small for a firefighting shaft of the required dimensions, and enlarging a riser through every floor plate is a structural operation.

Each of those is a planning issue as well as a fire engineering one, because resolving it usually means altering the external envelope, and altering the envelope is what the planning permission controls. That is the reason the fire statement has to be developed with the planning drawings rather than after them.

Single stair buildings and the conversion question

Many existing blocks above 18 m have a single staircase, built to the standards of their day. Government has announced an expectation of a second staircase in new residential buildings above 18 m, with the detail delivered through the statutory guidance and with transitional arrangements.

How that expectation applies to the conversion of an existing building is the question to settle first, and it is one to settle with the Regulator and the building control body rather than to assume. As at the date of this article the position on existing buildings has continued to develop, so verify it against the current published guidance before the design is committed.

What is clear either way is the design consequence. Inserting a second stair into an existing frame costs floor area on every level, needs new openings in every floor plate, and often forces a change to the core position that ripples through the whole layout. If there is any prospect of it being required, test the layout with and without it at feasibility stage. Discovering the requirement after planning permission means a fresh application, not a variation.

External wall construction in an existing block

The external wall is where conversion schemes most often stall. For relevant buildings, the restriction on combustible materials in external walls introduced into the Building Regulations in 2018 governs what can be in the wall, and the practical question on an existing block is what is in it already.

A fire risk appraisal of the external wall construction, carried out to the code of practice published for that purpose, is the recognised route to understanding an existing facade. It requires intrusive opening up at a sufficient number of locations to characterise the build-up, including the insulation, the cavity arrangement and the cavity barriers.

Three outcomes are possible and all three need a planning answer. The wall may be acceptable as it stands, in which case say so and reference the appraisal. It may need remediation, in which case the remediation is external work that the planning application should include rather than leave to a later application. Or it may need replacement, in which case the elevations change and the planning submission is a different scheme.

Balconies deserve separate attention. Existing balconies on a converted block are a known route for external fire spread and their construction is often undocumented, so they belong in the opening-up programme.

Evidence where the records have gone

Record searches are worth more effort than most teams give them. Try the local authority building control file, which may hold the original approved drawings. Try the authority's planning file, which often holds elevations and sections not kept elsewhere. Try the original design practice if it still exists. Try the asbestos survey archive, because an intrusive asbestos survey records construction details incidentally.

Where the records cannot be found, say so and describe the search carried out. A statement that lists the archives searched and the dates searched is credible. One that simply asserts the construction is unknown is not.

The documentation held on a planning file also matters for the long-term record, and the question of what the planning file should hold on structural warranties applies to fire documentation in exactly the same way.

Presenting residual uncertainty honestly

This is the part that separates a statement that passes Gateway One from one that does not.

State the survey work completed, with dates and locations. State the assumptions made and why each one is reasonable. State the further investigation programmed before the building control application, with what it will test. And state what the design would need to change to if an assumption proves wrong, at least in outline.

A reviewer reading that has something to assess. A reviewer reading a confident description of an unsurveyed wall has nothing to assess and will say so.

The full fire engineering work belongs in the fire safety strategy prepared to BS 9991 or BS 9999, not in the planning-stage statement, and what the planning-stage document covers is set out on the fire statement page. A Fire Statement is a report type where a professional with the necessary fire engineering competence is legally required, and an AI-assisted draft is a starting point for that professional rather than a substitute.

PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval. For specialist technical reports, qualified professional input may be required. You can enter the building postcode to see which fire and structural reports a conversion is likely to need.