Daylight and Sunlight Assessments in Hillingdon

Hillingdon's officers write about daylight and sunlight more precisely than most. Policy DMHB 11 names the BRE guidance, names the rooms that count (living rooms, dining rooms and kitchens next door) and reminds everyone that the BRE figures are guidelines to be weighed in context. That shapes the work we do in the borough: rear extensions to terraces in Uxbridge, Hayes and West Drayton where the adjoining house's kitchen window is the question, and large house renovations in Northwood, Ickenham and Ruislip where the council is as interested in the daylight to a new basement bedroom as in the neighbours.

Pre-application advice in Hillingdon often narrows the issue to a single point, and our daylight and sunlight assessments are scoped to that point so you are not paying for a full neighbour study when the officer has asked about one room. The three examples below show how that works in practice.

Recent daylight and sunlight assessments in Hillingdon

21 Montague Road, Uxbridge, UB8 1QL: a stepped extension on a resubmission

A single storey rear extension and front porch to a terraced house in Uxbridge. The council had raised concerns about the original design's effect on the adjoining house, so the architect stepped the rear wall away from the boundary and asked for a BRE neighbour-impact assessment for the resubmission. We tested the adjoining windows for VSC, NSL and APSH, and the revised extension met the BRE guidelines at every neighbouring window tested.

Hillingdon approved the resubmitted application, reference 22985/APP/2026/361, on 18 June 2026.

42 The Drive, Northwood: daylight to two basement bedrooms

A wide-ranging renovation of a house in Northwood, including extensions and a new basement. The council accepted the extensions had no significant effect on the neighbours, but questioned whether two basement bedroom suites, lit by a cut-away lightwell, would have adequate natural light under London Plan Policy D6. We scoped the report to that one concern and tested the two bedrooms for Spatial Daylight Autonomy and Sunlight Exposure through the lightwell; no design change was requested.

Hillingdon approved the application, reference 29969/APP/2025/1396, on 29 August 2025.

10 Beacon Close, Uxbridge, UB8 1PX: extensions tested against both neighbours

A single storey rear and side extension with a first-floor rear extension under pitched roofs, a new rear patio and porch alterations, on a house with neighbours either side who both needed to be assessed. We built the test model from the owner's own model of the house and re-tested when the design was revised, so the final report matched the drawings submitted.

Hillingdon approved the application, reference 9174/APP/2026/522, on 22 April 2026.

What Hillingdon planning officers look for

Hillingdon determines applications against its Local Plan, Part 1: Strategic Policies (2012) and Part 2: Development Management Policies (January 2020), read with the London Plan. The key policy is DMHB 11, Design of New Development, which requires that proposals do not adversely affect the amenity, daylight and sunlight of surrounding properties. Its supporting text is specific about method: the council expects the impact to be assessed using the most recent version of the BRE's Site layout planning for daylight and sunlight, and it identifies living rooms, dining rooms and kitchens as the rooms to be tested in adjoining dwellings.

The policy also builds in judgement. Reflecting the NPPF and the London Plan, it recognises that the BRE figures are guidelines rather than fixed limits and that a degree of flexibility is appropriate, particularly where a scheme makes efficient use of land, so results are weighed in context and a well-reasoned report carries real weight. For new rooms, including basements, officers rely on London Plan Policy D6 for adequate daylight and outlook. Hillingdon no longer maintains a standalone residential extensions design guide; the relevant guidance sits in the Local Plan. The Local Plan is at hillingdon.gov.uk/local-plan and the wider planning policy pages at hillingdon.gov.uk/planning-policy.

When you need an assessment in Hillingdon

• A rear extension to a terrace in Uxbridge, Hayes, Yiewsley or West Drayton, where the adjoining house's kitchen or living-room window sits close to the new wall
• A resubmission after the council has raised the effect on a neighbour, where a stepped or lowered design needs to be shown to meet the BRE guidelines
• A basement or lower-ground bedroom in Northwood, Ickenham, Ruislip or Harefield, where pre-application advice has raised Policy D6 and adequate natural light to the new rooms
• Side and rear extensions to a detached or semi-detached house where both neighbours need assessing
• A new house or flats on a backland plot or former workshop in Eastcote, Ruislip Manor or Hillingdon village, where neighbours and new homes are tested together
• Any application where a Hillingdon officer has cited DMHB 11 or asked for a proportionate daylight and sunlight assessment

How we work

Nick Maslen scopes the job, agrees a fixed fee up front and keeps the report to the question the officer has actually asked. Milica or Ana builds the 3D model, reusing your Revit or SketchUp model where you have one, and runs the BRE 209 tests, usually within 4–5 working days of receiving the information we need; re-tests on revised drawings are quick and modestly priced. The four neighbour tests are:

• VSC (Vertical Sky Component): the sky still visible from each neighbouring window
• NSL (No-Sky Line): daylight distribution within each neighbouring room
• APSH (Annual Probable Sunlight Hours): annual and winter sunlight to windows within 90 degrees of south
• Sun on ground: the share of a garden receiving two hours of sun on 21 March

New rooms are tested for Spatial Daylight Autonomy and Sunlight Exposure. The tests are explained on our VSC, NSL and APSH page and the thresholds on our BRE guidelines page.

Frequently asked questions in Hillingdon

Hillingdon's pre-app only raised the basement bedrooms. Do I need a full report?

No. A focused internal assessment of the rooms in question answers a Policy D6 point, as at The Drive, at a fraction of the cost of a full neighbour study.

Which neighbouring rooms does Hillingdon test?

DMHB 11 names living rooms, dining rooms and kitchens in adjoining dwellings, so those are the windows we concentrate on, with bedrooms included where they are the closest to the proposal.

Can a report be submitted close to the decision date?

Yes. At Montague Road the final report went to the officer on the council's extended decision date; if the timing is tight tell us and we will plan the draft and final around it.

Get a fixed-fee quote

Send drawings and the address through our contact page or use the price calculator for an instant figure; Nick is on 01962 809155 and nick@sunlightassessments.co.uk. For sites east of the Yeading Brook, see our Ealing page.