Dry riser inlets on a constrained street frontage
The inlet cabinet is 600 mm of steel door that has to appear on your street elevation, within sight of where the fire appliance will stand. Decide where before the elevation is drawn.
Approved Document B expects a dry riser inlet to sit within 18 metres of, and within sight of, the position where the pumping appliance will stand. That single sentence decides the dry riser inlet position on most urban schemes, because it ties a visible cabinet on your street elevation to a spot in the carriageway that the highway authority controls. Get it wrong and the inlet ends up in the middle of a shopfront, or in a position the fire authority will not accept, and the elevation that was consented is not the elevation that gets built.
A rising main is required where a floor sits more than 18 metres above fire service vehicle access level, and a wet rising main where a floor is more than 50 metres above it. So the question arrives on almost every residential block above six storeys.
What the inlet has to achieve
The inlet is the point at which the fire service pumps water into the building's dry main. Four requirements govern its position.
- Within 18 metres of the appliance parking position, so a hose can reach.
- In sight of that position, so the pump operator can see the inlet being used.
- Openable by the fire service without a lock that only building staff can release, which in practice means a cabinet secured to the fire service standard.
- Clearly identified, with signage that reads from the appliance position rather than from two metres away.
The cabinet itself is the awkward part. A two-way inlet needs a box in the order of 600 mm square, and a four-way inlet needs more. It has a hinged steel door that swings outwards, so it cannot sit behind a planter, a cycle stand or a bin store, and it cannot be obstructed by parked cars on a footway build-out.
Fixing the appliance position first
Work backwards from the carriageway. The appliance standing position depends on the road, not the building, and the constraints are real.
| Frontage condition | Consequence for the appliance position |
|---|---|
| Clearway or bus lane | Standing may not be acceptable to the highway authority |
| Segregated cycle lane at kerb | Appliance stands further out, so the 18 metres is measured from further away |
| Loading bay or parking bays | Usable, but the bay position fixes the inlet location |
| Footway build-out or tree pits | May prevent hose deployment even where the appliance can stand |
| Private forecourt | Best option, provided access width and carrying capacity are met |
The access route to that position has its own requirements on width, headroom, turning and carrying capacity for an appliance, which are in Approved Document B and which the fire authority will apply. A route that works on the drawing and fails once the refuse strategy, tree pits and level changes are added is a coordination failure rather than a fire engineering one.
Draw the appliance position on the site plan with an 18 metre radius from it. If the inlet falls outside that circle, something has to move, and it is easier to move the inlet than the road.
Conflicts with shopfronts and heritage frontages
On a mixed use block the ground floor frontage is commercial, and the tenant will not thank you for a steel cabinet in the middle of their glazing. On a listed or locally significant frontage, cutting a 600 mm recess into historic fabric needs listed building consent and may not get it.
Five approaches, roughly in order of how well they usually work.
- Place the inlet on a return elevation or in a service door recess that still falls within the 18 metre radius. Often possible on a corner site and almost never considered.
- Recess the cabinet into a reveal, a pilaster or a pier, where the depth of masonry allows it, with a door faced to match the surround.
- Integrate the cabinet into a gate, railing or screen that forms part of the frontage design, rather than into the wall.
- Surface-mount the cabinet in a location chosen for the composition, painted or finished to recede, accepting that it will be visible.
- Build a freestanding cabinet within a forecourt or landscaped zone, which keeps it off the building entirely.
Where the building is listed, the intervention is a heritage decision as much as a fire one, and the balance between escape and firefighting provision and historic fabric is the subject of the note on fire safety in listed buildings. Pick the least harmful option that works, and evidence why the alternatives were discounted.
Showing the position on the planning drawings
This is the part that gets missed, and the reason a consented elevation and a built elevation differ.
- Mark the inlet cabinet on the street elevation, dimensioned, with the proposed finish noted.
- Mark it on the ground floor plan with the door swing shown.
- Mark the appliance standing position on the site plan, with the 18 metre radius and the hose route.
- Note the signage position and its size.
- Where the cabinet is recessed into historic fabric, provide a detail at a scale that shows the reveal and the fixings.
An officer who can see all five will condition materials and move on. An officer who sees a clean elevation, and then receives a technical design with a steel box in the shopfront, will ask for an amendment application, and the applicant will have lost the argument before it starts.
The same logic applies to every element of the firefighting provision that surfaces on the outside of the building. Hydrant positions, the firefighting shaft's roof termination and the smoke control terminations all belong on the submitted drawings, and the Design and Access Statement should carry the same positions as the fire drawings.
Agreeing the position with the fire authority
Talk to the fire and rescue authority's fire safety team before the elevations are fixed. They are a consultee under the Building Regulations regime rather than a planning consultee, but they will comment on access and inlet positions, and their view is easier to accommodate at concept stage than at technical design.
Where Article 9A applies, the Health and Safety Executive as the Building Safety Regulator will look at fire service access and water supplies at Planning Gateway One, so the inlet and appliance positions feed directly into that response. A Fire Statement is a report where a professional with the necessary fire engineering competence is legally required, and PlanScope's Fire Statement draft is a starting point for that professional rather than a substitute for them. The later Fire Safety Strategy carries the detailed design of the main itself.
Two things to confirm in that conversation. Whether the authority accepts the proposed appliance standing position given the road layout, because their operational view can differ from a drawing. And whether the available water supply at the hydrant nearest that position gives the flow the building needs, since reinforcing a main is a utility exercise with a lead time.
The honest uncertainty is how much latitude individual fire authorities allow on the sight line requirement where street trees or a projecting canopy intervene. It varies, it is a matter of operational judgment, and it is worth asking rather than assuming the drawing settles it.
Enter your postcode on PlanScope to see which reports a tall residential scheme is likely to need.
This is general guidance, not legal advice. For specialist technical reports, qualified professional input may be required. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.
Frequently asked questions
How close must a dry riser inlet be to the fire appliance?
Approved Document B expects the inlet to be within 18 metres of, and in sight of, the pumping appliance parking position. Both limbs matter: an inlet 12 metres away but hidden behind a projecting canopy or a street tree may not be accepted. Draw the appliance position and the radius on the site plan.
When is a dry riser needed?
Where a floor of the building sits more than 18 metres above fire service vehicle access level. Above 50 metres a wet rising main is expected instead. In practice that means most residential blocks above six storeys need a dry riser and therefore an inlet cabinet on an accessible external face of the building.
Can the inlet cabinet go inside the building?
It has to be reachable by the fire service without help from inside the building, so it is normally in an external wall face or in a cabinet within an accessible recess. A position inside a locked lobby defeats the purpose. Use a cabinet secured to the fire service standard so their own crews can open it.
How do you deal with an inlet on a listed frontage?
Look for a return elevation or service recess within the 18 metre radius first, then a recess in a reveal or pier with a matching door face, then integration into a gate or railing, then a freestanding cabinet in a forecourt. Listed building consent is needed for any intervention, and the least harmful workable option has to be evidenced.
Who decides whether the appliance position is acceptable?
Operationally the fire and rescue authority, and the highway authority controls whether standing is permitted on that stretch of road. Where Article 9A applies, the Health and Safety Executive will also consider fire service access at Planning Gateway One. Raise it with all three before the elevations are fixed.
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.