Tall building fire design and what planning controls

Planning does not approve a fire strategy. The detailed fire engineering is settled at Gateway Two with the Building Safety Regulator, long after permission is granted. What planning does is fix the things the fire strategy will later have to work with: the footprint, the core position, the storey height, the external wall build-up, the plant space at roof level, and whether a fire appliance can get close enough to the building.

Those decisions are extremely expensive to revisit. A core moved three metres at Gateway Two changes every floor plate, and if the planning permission was granted on the earlier arrangement the change may need a fresh application. So the practical question for an architect is which fire-driven decisions have to be right before the application is submitted.

Which decisions are fixed at planning stage

Article 9A of the Town and Country Planning (Development Management Procedure) (England) Order 2015 requires a fire statement with applications for development involving a relevant building, which in broad terms means a building containing two or more dwellings or educational accommodation that is 18 metres or more in height or has seven or more storeys. The Health and Safety Executive is a statutory consultee on those applications, which is Planning Gateway One.

The fire statement is submitted on the form published for the purpose, and it asks about the site, the building, access and water supplies, the principles of the fire strategy, and how fire safety has influenced the layout and design. It is a design intent document rather than a full strategy.

What it locks in, in practice, is the site-wide and massing-level decisions. Everything in the list below costs less to fix now than later.

1. Building height and the number of storeys, because thresholds in the Building Regulations turn on them.
2. Core position and the number of stairs.
3. Plan depth from the core to the furthest point of each floor.
4. Fire appliance access routes, hardstanding positions and the distance from a pumping appliance to the riser inlet.
5. External wall construction and balcony arrangement at a level of detail sufficient to show the restrictions have been understood.
6. Roof level plant space for smoke ventilation.

Core position, shafts and plan depth

The firefighting shaft is the organising element of a tall residential plan. It contains the firefighting lift, the protected stair and the lobby, and its position sets travel distances from every flat entrance door.

Approved Document B has been amended to require a second staircase in new residential buildings above 18 metres, with transitional arrangements attached to the change, so check the current edition and the transitional dates before fixing a single-stair plan. The consequence for a planning submission is not subtle. Two stairs plus a firefighting lift and a lobby consume a substantially larger core area, and on a small footprint that can reduce the net internal area per floor enough to change the scheme's viability.

Plan depth follows from the core. Travel distance limits mean a deep floor plate with a single central core produces corridors that cannot comply, and the usual outcomes are a second core, a shorter plan, or a reduction in the number of flats per floor. Resolve that before the application, because the alternative is a permission for a floor plate that cannot be built out as drawn.

The arithmetic also catches buildings just under the threshold, where the design is pushed to 17.9 metres to avoid the regime. That strategy has its own problems, which we look at in our note on fire evidence for a building just below the threshold.

Fire service access on a tight urban plot

This is where planning and fire engineering collide most visibly, because access requirements consume external space the scheme wants for landscape, servicing or trees.

Four demands have to be accommodated on the site plan. A route capable of carrying a fire appliance, with the turning geometry it needs. Hardstanding positioned so that a pumping appliance stands within the required distance of the riser inlet. Hydrant provision within reach, coordinated with the water undertaker. And, for a building with a firefighting shaft, access to the shaft entrance from that hardstanding.

Show these on a dedicated drawing rather than describing them. An appliance tracking diagram, the hardstanding dimensioned, the riser inlet marked, and the hydrant positions noted. Officers and the statutory consultee both read that drawing, and its absence generates a request for information that costs weeks.

The conflicts that arise are predictable: a tree root protection area under the required hardstanding, a basement slab that cannot carry appliance loading, a level change that defeats the approach gradient, or a podium deck where the access route needs to be. Each of those is solvable at design stage and awkward afterwards.

Facade design and material restrictions

The Building Regulations restrict the use of combustible materials in the external walls of relevant buildings above 18 metres, and the scope of buildings caught has been extended since the restriction was introduced. Balconies, specified attachments and insulation are all within the controlled envelope.

For planning, the consequence is on the elevations. Timber cladding, certain rainscreen systems, and some balcony arrangements that would read well in a design review are not available on a tall residential building, and submitting elevations that depend on them means either a redesign or a material change after permission. Get the palette confirmed with the fire engineer before the elevations are finalised.

The honest position is that this narrows the architectural options at height, and pretending otherwise produces consented schemes that get rebuilt on paper between Gateway One and Gateway Two.

Smoke control and the plant it needs

Smoke control strategies for residential corridors range from a natural smoke shaft to a mechanical smoke ventilation system, and the choice has planning consequences because mechanical systems need plant, and plant needs space, access and acoustic treatment.

A mechanical system typically requires a shaft running the full height of the building and equipment at roof level. That competes with lift overruns, water tanks, photovoltaic arrays, green roof area and the amenity terrace, and it affects the roofscape the planning officer is assessing. Allocate the area on the roof plan at application stage with a dimension, rather than noting that plant will be accommodated.

Noise from roof plant to the nearest residential windows, including those in the same building, is an issue the environmental health officer will raise. Specify it as a limit at the receptor rather than a plant selection.

Coordinating with the fire statement

The fire statement and the Design and Access Statement should tell the same story, and the common failure is that they are written by different people from different drawing revisions. Check that the stair count, the core arrangement, the access route and the material strategy match in both.

The Fire Statement is a report type where the law expects an author with the necessary fire engineering competence: the requirement arises under Article 9A of the Development Management Procedure Order 2015 within the Building Safety Act 2022 framework, and a competent professional is legally required rather than merely advisable. The same applies to a Fire Safety Strategy prepared to the relevant British Standard. PlanScope can draft the planning narrative and structure as a starting point for that professional, and it is not a substitute for one.

Changes that need a fresh application

Minor adjustments can sometimes be handled as non-material amendments, and condition variations deal with details reserved by condition. But a change to the core position, the stair count, the storey height or the external material palette is normally material, and it may require a new application with fresh consultation of the statutory consultee.

Two habits reduce the risk. Design the core and the access arrangement with the dual-stair requirement and the material restrictions applied from the outset, even where the scheme currently sits below a threshold, since thresholds have moved more than once. And agree with the fire engineer which elements of the submitted design are fixed and which are indicative, then describe them that way in the application documents so that later development of the detail does not read as a departure.

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. Enter your postcode on PlanScope to see which reports a tall building application is likely to need.