Daylight and Sunlight Assessments in Cambridge

Our Cambridge work splits between the city and its villages. Inside the city it is often a small building squeezed into a tight plot, a garden room behind a school or college building, a rear extension in Romsey, Petersfield or Chesterton, where the neighbouring house is a few metres away. Out in South Cambridgeshire, in villages such as Landbeach, Hardwick, Histon and Cottenham, it is more often a two-storey extension or one or two new houses beside an existing home, where a single neighbouring window becomes the whole planning question.

Both councils are served by one planning team, the Greater Cambridge Shared Planning Service, and its case officers tend to ask precise questions: which window, which garden, which rule of thumb has been broken. A report that answers that question with the full BRE tests is usually what moves an application forward. Our main daylight and sunlight assessment page explains what a report contains.

Recent daylight and sunlight assessments in Cambridge

High Street, Landbeach: answering a 45-degree query on one window

A two-storey rear extension to a house in Landbeach drew a query from the case officer: on the drawings it broke the vertical 45-degree rule at a ground-floor bedroom window in the neighbouring house. We ran VSC, No-Sky Line and APSH for that window. The bedroom met the BRE guidelines for daylight, with almost the whole room still seeing sky, and for annual sunlight. The only effect was on winter sunlight, from an already low starting point, to a bedroom, which the BRE guide treats as less sensitive than a living room, so the effect was minor.

St Neots Road, Hardwick: finding the setback that keeps a neighbour's bedroom within the guidelines

Two new detached houses were proposed beside an existing house on Westside, off the St Neots Road, and the case officer was concerned about its ground-floor, west-facing bedroom. With the second new house 2.2 metres off the boundary, the bedroom fell short of the BRE guidelines, retaining 0.68 of its former VSC and 0.63 of its former daylight distribution against the 0.8 guideline. Moving the new house a further 2.8 metres from the fence, 5.0 metres in total, brought the bedroom back within the guidelines, and that was put to the architect as a concrete design change.

Panton Street, central Cambridge: a garden room close to the Saxon Street gardens

A school wanted to add a garden room near its northern boundary, close to homes on Saxon Street, and the planning officer asked for a sunlight assessment of the adjoining homes. We tested the windows and gardens of three neighbouring properties: the scheme met the BRE guidelines. The gardens already received little or no direct sun on 21 March, so the garden test showed no meaningful change, and the report explains in plain English why a starting point of zero still means no material loss.

What Greater Cambridge planning officers look for

Applications are decided by the Greater Cambridge Shared Planning Service on behalf of Cambridge City Council and South Cambridgeshire District Council. Until the emerging Greater Cambridge Local Plan is adopted, the development plans are the Cambridge Local Plan (2018) for the city and the South Cambridgeshire Local Plan (2018) for the villages.

In the city, the design policies in the Cambridge Local Plan, including Policy 58 on altering and extending existing buildings, expect proposals to protect neighbours from loss of light, overshadowing and an overbearing presence. In South Cambridgeshire, Policy HQ/1 (Design Principles) asks development to protect the amenity of neighbouring occupiers, including from loss of daylight. Both are backed by supplementary planning documents on design and residential development, and both rely on BRE BR 209 (2022 edition) for the measurable tests.

Officers often begin with the 25- and 45-degree rules of thumb. Those are screening checks: if a scheme breaks one, the BRE guide says the next step is the full VSC, NSL and APSH tests, which is what we provide. Our article on the 45-degree rule explains why.

• Greater Cambridge local and neighbourhood planning
• Greater Cambridge planning document library (local plans)
• Supplementary Planning Documents and other guidance

When you need an assessment in Cambridge

• Rear and side extensions in the terraces of Romsey, Petersfield, Mill Road and Chesterton, where neighbouring windows sit close to the boundary
• Two-storey extensions in South Cambridgeshire villages where the officer has flagged a 45-degree breach on a single window
• One or two new houses beside an existing home in villages such as Hardwick, Histon and Cottenham
• Garden rooms, teaching buildings and outbuildings on school and college sites that back onto homes
• Apartment schemes around Cambridge North, the Biomedical Campus and the city centre

How we work

We model your scheme and its neighbours in 3D from drawings, mapping and photographs, run the BRE tests and share the results before the report is written, so the design can be adjusted if needed. The fee is fixed and agreed up front; the report usually takes 4–5 working days from final drawings, and we can work to an extension-of-time deadline. The tests are:

• Vertical Sky Component (VSC): how much sky a neighbouring window can see
• No-Sky Line (NSL), or daylight distribution: how far daylight reaches into the room
• Annual Probable Sunlight Hours (APSH): annual and winter sunlight to windows facing within 90 degrees of south
• Sun on ground: whether at least half of a garden gets two hours of sun on 21 March

See our VSC, NSL and APSH page for how each test works and our BRE guidelines page for the thresholds.

Frequently asked questions in Cambridge

The officer says our extension breaks the 45-degree rule. Does that mean it will be refused?

No. The 45-degree rule is a quick screening check. The BRE guide says that where it is broken, the full tests should be run, and those often show the window still meets the guidelines or that the effect is minor.

Is South Cambridgeshire treated differently from the city?

The same shared planning service handles both, but the policies differ: the Cambridge Local Plan in the city, the South Cambridgeshire Local Plan in the villages. We cite the right one in the report.

The neighbouring garden gets almost no sun already. How is that judged?

The BRE garden test compares before and after. If a garden starts at or near zero, the proposal cannot make a meaningful difference, and we explain that in plain English so the officer can see why. We cover similar cases in Milton Keynes.

Get a fixed-fee quote

Send us your drawings and the officer's comments through our contact page, or get an instant figure from the price calculator. You can also call Nick on 01962 809155 or email nick@sunlightassessments.co.uk.