Fire safety in HMO conversions at planning stage

HMO conversion fire safety is not assessed by the planning system. Planning decides whether the use is acceptable. Fire safety is decided under the Building Regulations when you carry out the work, and under the Housing Act 2004 licensing regime when you let the rooms. A case officer will not read your fire strategy, and a refusal will not cite escape distances.

That split is useful to understand, because the fire requirements still reshape your drawings before you ever submit them. Protected stairs eat floor area. Escape windows change elevations. A room that becomes an inner room loses its bedroom use. By the time the layout satisfies the fire requirements, the scheme the planning officer sees is a different scheme, and getting that sequence the wrong way round costs a round of revisions.

What planning assesses and what licensing assesses

Three regimes apply to a house in multiple occupation, and they do not overlap as much as landlords expect.

Planning permission does not confer a licence. A licence does not confer planning permission. And a building control completion certificate confirms neither. Landlords who have been refused a licence after obtaining permission are usually the ones who treated the three as a single process.

The one planning document that does deal with fire is the Fire Statement, required at Planning Gateway One under Article 9A of the Development Management Procedure Order 2015 for relevant buildings within the Building Safety Act 2022 framework. That means buildings of 18 metres or more, or seven or more storeys, containing two or more dwellings. It must be prepared by someone with the necessary fire-engineering competence, and an AI-assisted draft is a starting point for that professional rather than a substitute. Most HMO conversions in houses and small blocks fall well below the threshold, so the Fire Statement is not triggered. In London, however, the London Plan requires a fire statement for major development as a matter of policy, which is a separate requirement from Gateway One.

Escape routes and the effect on layout

The fire principle for a converted house is that occupants should be able to reach a final exit along a route protected from the rooms they are escaping past. In a two or three storey terrace that normally means a protected stair enclosure: fire-resisting construction around the stairwell, self-closing fire doors to every room opening onto it, and a clear route to the front door.

The layout consequences follow directly:

• The hallway and stair must stay as circulation. Borrowing the hall to widen a ground floor bedroom is the first idea most people have and the first one to be abandoned.
• Any room you can only reach by passing through another room is an inner room, and inner rooms are generally unacceptable as bedrooms without a separate escape route or window.
• Open-plan ground floors, which sell well in a family house, work badly in an HMO because the stair discharges into the risk room.
• Kitchens on the escape route need particular attention, which often pushes the kitchen to the rear and the lounge to the front.

None of that is a planning matter in itself. But each of those moves changes the room count, and the room count is what the planning application is actually about.

Room sizes, protected stairs and lost space

Mandatory licence conditions set minimum sleeping room floor areas. The figures are 6.51 square metres for one person over the age of ten, 10.22 square metres for two people over ten, and 4.64 square metres for a child under ten. Space with a ceiling height below 1.5 metres does not count towards the measurement.

Put those two things together and a loft room with a shallow pitch can measure 9 square metres on plan and fail. The useful area is what lies under 1.5 metres of headroom or more, and a protected stair enclosure at the top of the flight takes a slice out of exactly the part of the room with the most headroom. The structural limits on a terraced house loft conversion interact with this, because raising the ridge is often the only way to recover the area and that is a planning application in its own right.

Work the areas in this order and you avoid most redesign:

1. Fix the escape strategy and the stair enclosure position.
2. Draw the fire-resisting walls at their built thickness, not as single lines.
3. Measure each sleeping room excluding anything under 1.5 metres of headroom.
4. Compare against the licensing minimum for the intended occupancy of that room.
5. Only then count the rooms for the planning application.

Article 4 directions and the use class question

The planning question is which use class you are moving to. A small HMO occupied by three to six unrelated people is Class C4. A larger HMO is sui generis and needs full planning permission.

Part 3 of Schedule 2 to the General Permitted Development Order 2015 permits a change from C3 to C4 without an application, which is why small conversions often proceed quietly. That right is the first thing councils remove by Article 4 direction, particularly in university towns and in wards with concentrations of shared housing. Where a direction is in force, a C3 to C4 change needs a planning application and will be assessed against a concentration policy, often expressed as a percentage of HMOs within a defined radius.

Check the direction's wording rather than its summary. Directions vary in the area they cover, the classes they withdraw and the date they took effect, and a scheme that complies with the policy in one ward can fail two streets away.

Licensing amenity standards that shape the drawings

Mandatory licensing applies to HMOs occupied by five or more people forming two or more households. Many authorities operate additional licensing schemes that bring smaller HMOs in too, so check whether a scheme is in force before assuming a three-person let is unlicensed.

Licensing standards go beyond room sizes. Councils publish amenity standards covering the number of bathrooms and WCs per occupant, kitchen worktop and storage provision, waste storage and sometimes cycle parking. Read those published standards at design stage, because several of them have planning consequences: bin stores and cycle stores appear on the site plan, and a bathroom added to meet the ratio may need a new window or a soil vent pipe on an elevation.

Sound insulation sits in the same category. It is a Building Regulations matter, but the construction build-up affects room dimensions, which feeds back into the licensing areas.

What to submit with the application

For a C4 or sui generis HMO application, the drawings carry the argument. Submit existing and proposed floor plans with each room labelled by use and annotated with its floor area, elevations showing any new or altered openings, and a site plan with bin and cycle storage shown to scale.

Then write the case. A short Planning Statement should address the concentration policy with actual numbers, the parking position with reference to the local standard, waste storage capacity, and the amenity relationship with adjoining houses. Where the authority has a published HMO policy with a percentage threshold, state the figure your scheme produces and show your working.

Avoid describing the fire strategy in the planning submission. It invites questions the planning officer cannot answer and creates an inconsistency risk if the Building Regulations design changes later. If fire-driven features are visible, such as an external escape stair or an enlarged window, show them on the elevations and explain their design in appearance terms.

For larger or more complex buildings, a Fire Safety Strategy to BS 9991 is a fire-engineering document and must be prepared by a competent fire engineer. It belongs with the Building Regulations submission rather than the planning application, unless the building is one where Gateway One applies.

Conditions and what follows approval

Expect conditions on approved plans, waste and cycle storage, and sometimes on occupancy. Some authorities condition the maximum number of occupants or bedrooms, which matters because exceeding it becomes a planning breach as well as a licensing one.

What usually does not appear is a fire condition, and you should not invite one. A condition requiring fire details to be agreed duplicates the Building Regulations and leaves you discharging a condition for something building control has already approved.

After permission, three things run in parallel: the Building Regulations application, the licence application, and the works themselves. The licence application needs the completed layout and the fire precautions in place, so sequence the inspection after practical completion rather than before.

Enter your postcode on PlanScope to see which supporting documents an HMO conversion application is likely to need.

This is general guidance, not legal advice. Licensing standards and Article 4 directions vary by authority, so check the position with your local planning authority, the housing team 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.