Evacuation strategy and the planning interface

The evacuation strategy for a planning application is not the fire engineering document. It is the set of decisions about how people leave the building that fix the core arrangement, the stair count, the lift provision and the fire service access before the planning drawings are frozen. Getting those right at planning stage is what stops a Gateway Two redesign from unravelling a permission.

Where Article 9A of the Development Management Procedure Order 2015 applies, a Fire Statement accompanies the application and the Health and Safety Executive is consulted as Planning Gateway One. The statement asks for the principles and approach to fire safety, not for a completed strategy, and knowing the difference saves a great deal of unnecessary work.

Strategies and what each implies for design

Four approaches cover most residential and mixed schemes, and each one has a plan consequence.

A stay put approach relies on compartmentation so that a fire is contained within the flat of origin and other residents remain in place. It is the conventional arrangement for blocks of flats and it depends on a protected escape route, which in plan terms means lobbied stair access and tightly controlled openings onto the stair.

Simultaneous evacuation assumes everyone leaves at once, which drives stair capacity and width rather than compartmentation alone. It is the fallback position where compartmentation cannot be relied on, and it changes the plan because stair width is a function of the population served.

Phased evacuation moves occupants floor by floor and suits commercial buildings with a management regime. Progressive horizontal evacuation moves occupants to an adjoining compartment on the same level, which is the normal approach in care and health settings and requires compartments sized to receive the people moved into them.

Say which one the design assumes, in one sentence, early in the statement. A statement that describes measures without naming the strategy leaves the consultee to infer it.

Where the strategy affects the planning layout

Five things on a planning drawing are decided by the evacuation strategy, and all five are expensive to change later.

• The number and position of stair cores, which follows from travel distances and from whether a single stair is acceptable at the building's height.
• The lobby arrangement at each core, which determines whether flats open directly onto the stair.
• Stair width, which follows from the population and the strategy.
• Lift provision, including whether any lift is designed as an evacuation lift.
• Fire service vehicle access and the position of the fire main inlet.

That last item regularly gets left to the landscape package and then conflicts with it. Approved Document B expects vehicle access for a pump appliance to within 18 metres of, and within sight of, the fire main inlet for a block of flats, with route widths, turning provision and carrying capacities set out for pump and high reach appliances. A hard landscape design with raised planters and a feature paving pattern across that route has to be reconciled with those requirements, and it is better reconciled before submission.

Evacuation lifts and core planning

An evacuation lift is a lift designed and protected so that it can be used to evacuate people during a fire, with a protected lobby, secondary power supply and controls for managed use. It is larger and more demanding of space than a passenger lift, and it sits inside the protected core.

In London, Policy D5 of the London Plan requires development proposals to provide at least one lift per core, subject to capacity assessment, as a suitably sized fire evacuation lift. That requirement has a plan consequence in every core, and on a compact point block it can be the difference between one lift and two.

Where a scheme has multiple cores of different sizes, test the smallest one first. A core that works with a passenger lift and fails with an evacuation lift usually needs the whole floor plate adjusting rather than a local change.

Inclusive evacuation provision

Stay put strategies historically left disabled residents without a plan, and that is no longer an acceptable position in either regulation or policy. The planning submission should show how people who cannot use stairs will leave.

The elements that appear on a planning drawing are the evacuation lift, refuge spaces at stair landings sized so that they do not obstruct the escape route, and clear step-free routes from the building to a place of safety outside. Management arrangements, including personal emergency evacuation planning, sit outside planning but the physical provision that supports them does not.

Where the scheme includes specialist accommodation such as older persons housing, the strategy is likely to be progressive horizontal evacuation, and the compartment sizing has to be shown. A plan with compartment lines drawn and areas noted answers more consultee questions than several pages of description.

What can be left to later gateways

A great deal, and the statement should say so explicitly rather than attempting a full strategy.

Detailed smoke control design, sprinkler or other suppression layouts, compartment line construction details, fire door specifications, cavity barrier positions and the fire engineering analysis supporting any departure from guidance all belong at Gateway Two under the Building Regulations. Committing to a specific smoke control solution at planning stage fixes a design choice that may change, and if the planning drawings show a shaft that the final design does not need, you have created an unnecessary variation.

What the planning submission does need to commit to is anything that affects the building's external form, its footprint, its access arrangements or the number of cores. Those are the matters the planning permission controls.

Where a building sits close to the 18 metre threshold, the calculation of height matters more than anything else in the statement, and the question of fire evidence for a building just below the threshold is worth settling before the floor-to-floor dimension is fixed. Basement accommodation raises its own escape questions, and safe egress from habitable basement rooms needs resolving at the same stage.

Explaining the choice in the statement

Write the statement so that a consultee can follow one thread from the strategy to the drawings. The order that works is the strategy, then the compartmentation or capacity assumption it depends on, then the physical provisions that deliver it, then the drawing references where each provision appears.

An illustrative example

A 16 storey residential building of 52 metres has two cores. The strategy is stay put with simultaneous evacuation of the affected floor and those above and below. Each core has a lobbied stair, one evacuation lift and one passenger lift, with refuge space at each landing outside the escape width. Fire service access is from a 4 metre wide route along the southern boundary, with the dry riser inlet 12 metres from the hardstanding and in direct sight of it. The hard landscape design was revised to remove a raised planter from that route. This example is illustrative rather than a real building.

A Fire Statement at Gateway One must be prepared by someone with the necessary fire engineering competence, and a Fire Safety Strategy to BS 9991 or BS 9999 is a fire engineering document in its own right. A licensed or competent professional is legally required for this work, and an AI-assisted draft is a starting point for that professional rather than a substitute.

One honest uncertainty: the regulatory framework around residential fire safety has changed repeatedly since 2020, including the staircase position and the scope of higher-risk buildings. Verify the current requirements and any transitional arrangements on gov.uk and with the Building Safety Regulator before fixing a design.

This is general guidance, not legal advice. Check the position with your local planning authority or a qualified professional before relying on it.

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