Which rooms count as habitable in a daylight assessment

Not every room in a flat gets assessed for daylight, and the decision about which ones do is made before a single calculation is run. That scoping decision changes results more than any modelling choice, which is why disputes about habitable rooms in a daylight assessment are usually disputes about room labels on a drawing.

BRE 209 sets out a hierarchy. Main living rooms carry the highest expectation, kitchens and dining rooms follow, bedrooms attract a lower one, and bathrooms, toilets, hallways, landings, stores, utility rooms and garages are not analysed at all.

The BRE position on room hierarchy

The guidance is written around the idea that different rooms have different daylight needs based on when they are occupied and what happens in them.

For existing buildings affected by a new development, the tests applied to windows serving those rooms are the familiar ones: vertical sky component at the window face, and the no-sky line contour within the room. Those are applied to main habitable rooms.

For rooms inside a proposed development, the 2022 edition of BRE 209 aligns with BS EN 17037 and works in target illuminance across a proportion of the room area, rather than the average daylight factor percentages that dominated earlier practice. Many local authority policies and validation lists still refer to average daylight factor targets of the order of 2 per cent for kitchens, 1.5 per cent for living rooms and 1 per cent for bedrooms, so a reviewer will often see both approaches in the same submission.

State which method has been used, and against which edition. A report that mixes the two without saying so is not reviewable.

Kitchens and kitchen diners

A kitchen has historically carried the highest numeric target of the three room types, on the reasoning that it is a task space used during the day.

The complication is the open plan layout that now dominates new flats. Where a kitchen, dining area and living area occupy one space, it is a single room for assessment purposes, and it should be assessed against the requirement for the most demanding use within it.

Two consequences follow, and both cut against the applicant.

The no-sky line has to be plotted across the whole open plan area, so the deep part of a 9 metre deep living-kitchen-dining space fails a test that two cellular rooms of the same total area would pass.

And where the open plan space is served by a single window wall, the daylight distribution towards the rear is poor by construction, so the design response is a wider window, a dual aspect, or a shallower plan rather than an argument about room classification.

Reviewers should check that the room boundary used in the model matches the boundary on the general arrangement drawing, including whether a peninsula or an island has been treated as a partition.

Bathrooms, hallways and utility spaces

These are outside the assessment. Bathrooms, WCs, en-suites, halls, landings, corridors, stores, utility rooms, garages and plant spaces are not habitable rooms, and BRE does not expect them to be analysed.

That has a practical use in design. Putting non-habitable rooms on the constrained elevation is a legitimate response to a difficult site, and it should be presented as a design decision rather than hidden.

It also has a limit. A layout that puts every habitable room on one over-shaded elevation and lines the good elevation with bathrooms will be seen for what it is.

Bedrooms and the lower expectation

Bedrooms attract the lowest numeric target of the three assessed room types, because they are largely occupied at night. That does not make them exempt, and a bedroom that fails badly still counts as a poor living condition.

For sunlight, the picture differs again. Annual and winter probable sunlight hours are assessed for windows facing within 90 degrees of due south, and BRE's view is that sunlight to bedrooms matters less than to main living rooms. So a north-facing bedroom is not usually a sunlight issue, while a north-facing single-aspect living room is.

Studio flats are the awkward case. A studio is a single habitable space performing living, sleeping and cooking functions, so it takes the most demanding target of the uses it contains.

Commercial and non-residential rooms

BRE tests are applied to non-domestic buildings where occupants have a reasonable expectation of daylight. Offices, schools, nurseries, consulting rooms and staff rest areas fall inside that. Retail floors, warehouses, storage, plant rooms and back-of-house areas generally do not, because daylight is not part of the expectation for those uses.

Where a new development affects an existing commercial building, the question is what the affected rooms are used for now and whether that use has a daylight expectation. An office converted to a gym has a different answer from an office still in office use.

Say which non-domestic rooms have been scoped in and which have been scoped out, and why. That single paragraph prevents most of the arguments a reviewer would otherwise raise.

Changing room use between application stages

Room labels move between application stages, and reviewers should look for it.

The patterns to watch:

1. a bedroom relabelled as a study, home office or flexible space, removing it from the assessment or reducing its target
2. a living room relabelled as a dining room where the numeric target is lower
3. an open plan space subdivided on a later drawing so the no-sky line is calculated across two smaller rooms
4. a habitable room shown with a partition that does not appear in the general arrangement or the sales layout
5. a room area shrunk to the point where it could not function as the use it is labelled with

Test the label against the room. Does the space meet the bedroom sizes in the nationally described space standard. Is there a window, a door swing and a wardrobe zone consistent with the labelled use. Does the marketing material describe the flat differently from the planning drawing.

Illustrative example: a submitted assessment reports compliance for a two-bedroom flat with one room labelled study. That room is 12 square metres with a window and a door off the hall, and the scheme is described elsewhere as three-bed equivalent. Assessed as a bedroom, it falls below the relevant target. The reviewer's recommendation is not to reject the report, but to require it to be rerun with the room assessed on its likely use.

How a disputed room use is resolved

There is no formal mechanism, so it is resolved by planning judgement on the evidence in front of the officer.

What carries weight: the approved plans, since those are what the permission is granted against and what a condition will tie the development to. The functional characteristics of the space, including its size, shape, window position and access. Consistency across the applicant's own documents. And whether the labelled use is plausible for the number of habitable rooms shown elsewhere.

The reviewer's job is to state the assumption, not to litigate it. Write the assessment with the room use you consider correct, report the result for the applicant's labelling as well, and let the officer decide which to rely on. A daylight and sunlight assessment that shows both readings is far more useful than one that quietly picks the favourable one.

Where amenity space is also affected, the same scoping discipline applies to the overshadowing study: say which areas have been included and on what basis. And where you are assembling the wider evidence base for a scheme, browse the report types to see what else the authority is likely to ask for.

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. Enter your postcode on PlanScope to see which amenity documents a scheme is likely to need.