Planning glossary

Vertical Sky Component VSC

The ratio of direct sky illuminance at the centre of a window to the illuminance on a horizontal plane under an unobstructed CIE standard overcast sky, expressed as a percentage. It is the primary BRE 209 metric for daylight impact assessment. BRE treats an absolute VSC above 27% as broadly acceptable, and a proposed/existing ratio above 0.8 (i.e. no more than 20% loss) as not a noticeable effect.

See: Vertical Sky Component explained · Understanding daylight and sunlight reports

Annual Probable Sunlight Hours APSH

A BRE 209 sunlight metric measuring the proportion of probable sunlight hours a window or amenity area receives over the year, with a separate winter (21 September to 21 March) sub-metric. BRE recommends at least 25% APSH annual and at least 5% APSH winter, with a proposed/existing ratio above 0.8 for new development to be considered broadly acceptable.

See: Shadow and daylight impact

No Sky Line NSL · Daylight Distribution

The contour inside a room separating points on the working plane that can still see some sky from points that cannot, after the proposed obstruction is in place. BRE 209 treats a reduction in the area that can see sky of more than 20% as a noticeable effect on daylight distribution, supplementing the VSC check at the window plane.

Material planning considerations

Factors the local planning authority may lawfully take into account when deciding a planning application. Material considerations include loss of daylight, sunlight, privacy, noise, overbearing impact, traffic, heritage, design and conflict with the adopted Local Plan and the National Planning Policy Framework. Loss of property value, loss of a private view and the identity of the applicant are not material considerations and do not carry weight in the decision.

See: How to formally object to a planning application

Article 15 DMPO

Article 15 of the Town and Country Planning (Development Management Procedure) (England) Order 2015 requires local planning authorities to publicise planning applications by site notice and neighbour notification, and for major applications by additional press notice. It is the statutory basis for the 21-day consultation period residents use to object.

BRE 209 BR 209 · BRE daylight and sunlight guide

The Building Research Establishment guidance Site layout planning for daylight and sunlight — A guide to good practice (3rd edition, 2022). It is the standard reference used by developers, consultants and councils for assessing daylight, sunlight and overshadowing impacts of new development on neighbouring windows, amenity areas and open space.

National Planning Policy Framework NPPF

The government's primary planning policy document for England, last updated December 2024. Section 38(6) of the Planning and Compulsory Purchase Act 2004 requires applications to be determined in accordance with the adopted development plan unless material considerations indicate otherwise; the NPPF is a material consideration in every English planning decision.

Primary source: gov.uk — National Planning Policy Framework

Local Planning Authority LPA

The statutory body responsible for determining planning applications in its area — usually a London borough, district, unitary or metropolitan council. Some strategic applications in London are determined or called in by the Mayor of London (the GLA) acting as a second-tier LPA. Every LPA publishes its applications on an online planning portal, usually powered by Idox, Uniform or Agile.

Section 106 agreement S106 · Planning obligation

A legal agreement under section 106 of the Town and Country Planning Act 1990 between the applicant and the LPA, imposing planning obligations such as affordable housing contributions, highway improvements or public realm payments as a condition of planning permission. Separate from the Community Infrastructure Levy.

Section 73 variation S73

An application under section 73 of the Town and Country Planning Act 1990 to vary or remove a condition attached to an existing planning permission. A section 73 grant creates a new planning permission that sits alongside the original; the original remains live and can still be implemented.

Community Infrastructure Levy CIL

A charge levied by local authorities on new development to fund infrastructure, calculated per square metre of new floorspace against a published charging schedule. CIL liability is fixed by the charging schedule and is separate from Section 106 planning obligations, which are negotiated case by case.

Tree Preservation Order TPO

An order made by a local planning authority under the Town and Country Planning Act 1990 to protect specific trees, groups of trees or woodland considered to have amenity value. Works to a TPO tree require LPA consent; unauthorised works are a criminal offence. Conservation area trees enjoy similar (but not identical) protection by default.

Planning Inspectorate PINS

The government agency that determines planning appeals in England and Wales on behalf of the Secretary of State. Appeals by applicants against refusals, non-determination or conditions are heard by written representations, hearing or inquiry. Residents may submit representations at the appeal stage — a second opportunity to make a case against a scheme after the initial LPA objection window has closed.

Primary source: gov.uk — Planning Inspectorate

Rights of light

A legal easement, distinct from the planning daylight assessment, entitling a landowner to receive sufficient natural light through defined apertures of a building. A right to light is typically acquired by 20 years' uninterrupted enjoyment under the Prescription Act 1832 and is measured against the 0.2% sky factor (Waldram) test established in Colls v Home & Colonial Stores [1904]. Planning permission does not override a right to light.

See: Rights to light explained

0.8 ratio (BRE noticeable-effect threshold)

The ratio of proposed to existing VSC (or APSH) below which BRE 209 treats the effect on a window or amenity area as noticeable. A proposed/existing ratio of 0.8 means no more than a 20% reduction. Ratios below 0.7 are treated as significant. The same 0.8 ratio appears in rights of light methodology but with a different legal meaning and remedy.