Start with the route from the loft to outside
For a conversion creating a storey above 4.5 metres, Approved Document B requires the whole escape route to be addressed. If the stair opens directly into a living room or kitchen below, a fire there can affect the route used by the loft occupants. The design cannot be resolved by considering only the new flight and bedroom door. [1]
Give the designer accurate plans of every affected floor, showing doorways, partitions, cooking facilities and exits. Ask for the proposed escape route to be marked continuously from the loft to the final exit. This makes any gap in the intended protection visible before the loft layout is fixed. [1]
Option 1: enclose the escape route
The straightforward guidance route is a protected stair with the appropriate fire-resisting enclosure and doors. For an existing open-plan layout, paragraph 2.21 expressly refers to adding partitions to enclose the route. The exact arrangement still needs to preserve suitable access to the final exit. [1]
Compare the resulting ground-floor plan before rejecting separation. The decision is not simply 'open plan or a loft': a revised doorway or partition arrangement may retain useful connections while protecting the escape route. This is a design option to investigate, not an assurance that every existing layout can remain substantially unchanged. [1]
Option 2: the specified sprinkler alternative
Paragraph 2.23 describes an alternative with all of these components:
- Sprinkler protection to the open-plan areas.
- A fire-resisting partition and door separating the ground storey from the upper storeys, arranged so loft occupants can reach a first-storey escape window.
- Fire-resisting construction separating cooking facilities from the open-plan area. [1]
The guidance specifies the performance of that separation. It is not a sprinkler-only exemption and does not describe an entirely open kitchen, living space and staircase as automatically acceptable. The escape window also has to meet the relevant guidance; an ordinary small window is not enough. [1]
What about water mist?
The cited prescriptive loft alternative specifies sprinklers; it does not provide a general statement that any domestic water-mist system can replace them. A proposal relying on mist instead is an alternative design requiring supporting evidence rather than an automatic like-for-like substitution. [1]
Ask the fire-safety designer to identify the proposed system's role, the scenarios it addresses, the supporting test or assessment evidence, and how the complete layout meets the functional requirements. Obtain the building-control assessment before committing to a layout whose acceptability depends on that system. The basis for this approach is Approved Document B's provision for properly justified alternative fire-safety designs. [1]
Agree the complete specification
The coordinated design should identify the required doors and partitions, alarm provision, suppression arrangements where used, escape windows and relevant maintenance information. A quotation that only names a suppression product does not settle the remainder of the fire strategy. [1] [2]
Approved Document B's published fire-resistance classification changes take effect on 2 September 2029, subject to transition. Keep that future change separate from today's assessment of the open-plan layout, and re-check the relevant product specifications for later work. [1]