Higher-risk buildings: what the threshold changes at planning

A building is higher-risk for the design and construction regime under the Building Safety Act 2022 framework where it is at least 18 metres in height or has at least seven storeys, and contains at least two residential units, with care homes and hospitals also caught at that stage. Crossing that threshold pulls the scheme into a three gateway consent sequence, makes the Health and Safety Executive a consultee at planning stage, and locks down the ability to change the design once building control approval is given. The measurement therefore belongs in the first week of a project, not in the technical design phase.

Developers who treat this as a building control matter discover late that it is a planning and appraisal matter. Two of its consequences land on the drawings, and one lands on the programme.

How the threshold is defined and measured

Height is measured from ground level to the floor surface of the top storey, disregarding any storey consisting only of roof top plant or machinery. Storeys are counted on a similar basis, with below ground storeys and plant only levels treated separately from occupied floors.

Both limbs count. A building of seven storeys that comes in at 17 metres is caught, and so is a five storey building with unusually generous floor to floor heights that reaches 18 metres.

Read the current regulations for the definitions rather than working from a summary. The descriptions and the excluded building types have been set out in secondary legislation and refined since the Act, and the boundaries matter most exactly where a scheme sits closest to them.

Three measurement traps recur:

• Sloping sites, where ground level is not a single value and the measurement point has to be established deliberately.
• Podium and basement arrangements, where the level counted as ground is arguable.
• A top floor plant enclosure that raises the apparent height without raising the floor of the top occupied storey.

Establish the measurement with the design team and record the assumption in writing. A scheme that changes category between planning and building control is the worst outcome available.

What changes at planning stage

The visible change is the fire statement. Development involving a relevant building at 18 metres or more, or seven or more storeys, requires a fire statement on the published form under Article 9A of the Development Management Procedure Order 2015, and the Health and Safety Executive is consulted on it as Planning Gateway One. Without it the application is invalid.

The less visible change is design. A statement that says fire safety has shaped the layout has to be true, which means the fire engineer needs to be appointed before the plan is fixed rather than afterwards. Appliance access, standing space, hardstanding loadings, riser inlet positions and the assembly area all occupy land, usually the land you had drawn as landscape or parking.

Building height also brings other requirements into play at the same point: wind microclimate, daylight and sunlight to neighbours, and townscape assessment. None of those is caused by the higher-risk threshold, but they arrive together and they interact.

The gateway sequence after permission

Three gateways run in order.

1. Gateway One at planning, through the fire statement and the regulator's consultation response.
2. Gateway Two before building work starts, where the building control application for a higher-risk building goes to the Building Safety Regulator for approval rather than to a local authority or approved inspector.
3. Gateway Three at completion, where a completion certificate must be obtained before the building can be occupied.

The practical consequence is a hard stop between permission and construction. Work cannot start until Gateway Two approval is issued, and the statutory determination periods for that approval are set out in the building regulations rather than in planning legislation. Verify the current periods on the regulator's own pages before building a programme around them.

There is also a change control regime during construction. Certain changes need approval before they are made, and others must be recorded. A design and build contractor used to resolving details on site will find that habit expensive.

Design decisions that are hard to reverse

Four in particular.

Core arrangement. Where a second staircase is required, it occupies floor area on every level. The government confirmed a requirement for a second staircase in new residential buildings above 18 metres, reflected through changes to Approved Document B with transitional arrangements attached; verify the current position and dates on gov.uk. Adding a stair after planning permission reduces saleable area, changes the unit mix and usually needs a section 73 application.

Appliance access and hardstanding. The position is fixed by the distance to the building and by the loading the ground has to carry, so it cannot simply be moved to suit the landscape design.

Façade specification. Material choice on a higher-risk building is constrained, and a planning permission granted on the basis of a material that cannot be used produces a discharge problem or a variation.

Single stair contingency. A scheme designed at 17.9 metres to stay below the threshold has no margin. Any later increase in floor to floor height, in raised external levels or in the roof build up pushes it over.

Programme effects on a residential scheme

Add three things to the programme that a conventional scheme does not carry: the Gateway One consultation response inside the planning determination period, the Gateway Two approval period between permission and start on site, and the Gateway Three completion certificate before any unit can be occupied.

That last one has the sharpest commercial edge. Sales completions cannot happen before occupation is lawful, so a delay at Gateway Three delays receipts on the whole building rather than on a plot. Model it in the cash flow rather than assuming a handover date.

Where a site contains several blocks and only one crosses the threshold, phasing matters. Building the caught block last is often the better sequence, because the rest of the scheme is not held behind its gateways. The interaction between separate permissions on one site raises its own problems, so read the Hillside judgment on overlapping permissions before splitting a scheme into two applications for that reason.

Where to verify the current position

This regime has changed repeatedly since 2022 and it will change again. Treat any secondary source, including this one, as a pointer rather than an authority.

Check the Building Safety Act and the regulations made under it on legislation.gov.uk for the definitions. Check the regulator's own pages for the gateway procedures and the current determination periods. Check gov.uk for the Approved Documents and their transitional arrangements. And check the council's validation list, because local requirements sit on top of the national ones.

Follow reform news through the planning law timeline rather than an older summary, and use the report types to scope the wider evidence base a tall residential scheme needs.

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