Firefighting shafts, dry risers and the planning layout
A firefighting shaft is set early and is expensive to move later. This covers what the shaft contains, where the inlet has to sit relative to appliance access, and what the planning drawings should show at application stage.
The firefighting shaft is the single most layout-determining element in a tall residential building, and it is usually settled before anyone has drawn a flat. Get the planning layout wrong and the shaft either eats the floor plate or cannot be served by an appliance, and both problems surface after permission, when the fix costs a section 73 application and a redrawn unit mix. Approved Document B triggers a shaft where a building has a floor more than 18 m above fire service vehicle access level, or a basement more than 10 m below it, which captures most schemes that need a fire statement at Gateway One in the first place.
So the firefighting shaft planning layout is worth resolving in the same week as the massing, not in the month before submission.
What the shaft contains
A firefighting shaft is not a stair with a label. It is a protected enclosure containing a firefighting stair, a firefighting lobby at every level it serves, and a firefighting lift, with a rising main within the protected space and its own ventilation or pressurisation arrangement.
That bundle drives three things in plan. The core footprint, because stair, lift, lobby and riser cupboard all have to fit within the protected construction. The circulation beyond the lobby, since the lobby is the only route between the shaft and the accommodation. And the structural grid, because a shaft wants to run continuously through the building and sit on its own foundation arrangement.
Two cores or one is the first real decision. A single firefighting shaft serving a deep floor plate pushes travel distances up and often forces a corridor arrangement that compromises dual aspect. Two cores cost more in area but buy layout freedom and simultaneous evacuation options.
Inlet position and appliance access
Dry riser inlets are sited by reference to where the pumping appliance can park. Approved Document B expects access for a fire service vehicle to a point within 18 m of the inlet, with the inlet visible from that position. On a tight urban site that single dimension decides the entrance arrangement.
Work it through on the site plan at concept stage:
- Fix the appliance parking position, with the hardstanding dimensions and the loading the carriageway construction has to carry.
- Measure 18 m from it to the proposed inlet box and check sight lines, including any planting, bin store or substation in between.
- Check the approach gradient and the swept path for the appliance, including any gate, bollard or ramp.
- Confirm the route is on land within the application site. Appliance access across land you do not control is a problem that gets discovered at Gateway One.
- Coordinate with the hydrant positions and the water undertaker's capacity, which is a separate enquiry worth starting early.
The inlet box itself is a small object with outsized consequences for the entrance elevation. Architects who leave it to the services engineer end up with a stainless steel cabinet in the middle of a carefully composed façade.
Lobbies and the floor area they cost
Firefighting lobbies are where the area goes. Every storey served by the shaft needs a lobby of the minimum size set in Approved Document B, with doors that do not conflict, and in a residential building the lobby usually also has to work with the common corridor and any smoke control shaft.
On a small floor plate the arithmetic is unforgiving. A core with stair, lift, lobby, riser and smoke shaft can take a substantial share of a 400 m² plate, and the proportion worsens as the building narrows. That is why a proposal that works beautifully at 16 m becomes marginal the moment it reaches 18 m and picks up the shaft requirement.
The planning consequence is a design decision, not a technical one. Either accept a fatter core and fewer, larger units, or hold the unit count and accept a wider building. Resolve it before the application rather than discovering at Gateway One that the only way to make the numbers work is to lose a storey.
Wet risers, tanks and plant space
Above roughly 50 m of building height a dry rising main is no longer adequate and a wet riser with stored water and pumps is expected. That brings a tank room and a pump room, both of which need access, drainage, structural support and acoustic separation from habitable rooms.
Plant of that kind has to be located in the planning drawings because it affects the massing. A tank at roof level changes the parapet and the plant enclosure that the townscape assessment will be judged on. A tank at basement level competes with car parking, cycle stores and attenuation, and brings its own groundwater and structural questions. Neither position is free, and both are hard to insert after the elevations are fixed.
Sprinkler or suppression tanks sit alongside this and are often forgotten in the same way.
Showing the shaft on planning drawings
Planning drawings are not a fire strategy, and nobody expects shaft construction details on a 1:100 plan. What they should show is that the strategy is deliverable within the consented envelope.
| Drawing | What to show |
|---|---|
| Site plan | Appliance parking position, hardstanding, 18 m dimension to the inlet, approach route and gates |
| Ground floor plan | Core position, lobby, inlet box location, hydrant positions |
| Typical floor plan | Shaft outline, lobby, protected corridor, travel distances |
| Section | Shaft running continuously, tank and pump room positions |
| Elevations | Inlet box, ventilation openings and any smoke shaft terminations |
Label the shaft as a firefighting shaft rather than as a stair core. Reviewers at the authority and at the Health and Safety Executive read the drawings first and the statement second, and a labelled drawing answers half the questions before they are asked.
The Fire Statement submitted under Article 9A of the Development Management Procedure Order 2015 then describes the principles: site access, water supplies, the evacuation approach and the means by which the building will be reached and fought. It is not the place for detailed calculations, and padding it out with them tends to invite more queries rather than fewer.
Coordination with the evacuation strategy
The shaft and the evacuation strategy are one decision in two drawings. A stay-put strategy with a single stair depends on compartmentation and on the fire service reaching every level through the shaft. A simultaneous evacuation strategy, or a second stair, changes the core arrangement, the lobby pressures and the alarm design, and it changes the floor plate.
Where a second stair is being provided, say so in the fire statement and show both on the plans, including whether the second stair is also a firefighting shaft. Where evacuation lifts are proposed, show the lift lobby arrangement and the power supply route. The detail lands later in the Fire Safety Strategy prepared to BS 9991 or BS 9999, and that document is a fire engineering deliverable requiring a competent professional by law.
Queries the consultee raises
The Health and Safety Executive is a statutory consultee at Gateway One, and the recurring queries are practical rather than theoretical. Whether the appliance can actually reach the stated position given the gate, the ramp and the parking layout. Whether the 18 m dimension is measured to the inlet or to the core door. Whether firefighting access is maintained during a phased build. Whether the water supply has been confirmed with the undertaker. Whether the shaft serves every storey including plant levels and basements.
Answer those in the submission and the consultation is usually short. Leave them to be asked and the response adds weeks.
PlanScope can draft the structure and narrative of a Fire Statement from your project details and flag the facts that are missing, and a professional with fire engineering competence is legally required to complete and take responsibility for it. You can send a draft to a fire engineer to review it once the layout is settled. For specialist technical reports, qualified professional input may be required.
It is also worth scoping the reports a relevant building attracts early, because fire is rarely the only consultee on a scheme at this height.
This is general guidance, not legal advice; check the position with your local planning authority or a qualified professional before relying on it. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.
Frequently asked questions
When is a firefighting shaft required?
Approved Document B triggers a firefighting shaft where a building has a floor more than 18 m above fire service vehicle access level, or a basement more than 10 m below that level. The shaft encloses a firefighting stair, a firefighting lobby at each level and a firefighting lift, all within protected construction with its own rising main.
How close does the appliance have to get to the dry riser inlet?
Approved Document B expects fire service vehicle access to a point within 18 m of the dry riser inlet, with the inlet visible from the appliance parking position. That drives the position of the hardstanding, the gradient of the approach and any gated access, all of which appear on the planning site plan rather than in the building control submission.
At what height does a wet riser replace a dry one?
Dry rising mains are used up to around 50 m of building height, and above that a wet riser with a stored water supply and pumps is expected. The practical planning consequence is plant space: a wet system needs a tank room and pump room with access and acoustic separation, which has to be found in the massing rather than added later.
Does the fire statement cover riser positions?
The fire statement at Gateway One addresses the principles of fire safety relevant to the planning decision, including site access for the fire service, water supplies and the broad design approach. Detailed riser and shaft design belongs to the later fire safety strategy and building control submission, but the planning drawings must not foreclose it.
Can the firefighting shaft be moved after planning permission?
Rarely without consequence. The shaft sets the core position, the lobby depths and the floor plate efficiency, so moving it changes unit layouts, window positions and sometimes the external envelope. That usually means a section 73 application or a non-material amendment, and on a tight plan it can change the unit mix altogether.
Who should prepare this work?
A fire engineer with the relevant competence. The fire statement at Gateway One and any fire safety strategy to BS 9991 or BS 9999 are fire engineering documents, and a competent professional is legally required for them under the Building Safety Act 2022 framework and Article 9A of the Development Management Procedure Order 2015.
Sources and further reading
This article is general guidance about the planning system in England and, where stated, the rest of the UK. It is not legal or professional advice. Check your local planning authority’s validation requirements and take professional advice for your specific site.