Hillingdon planning guide: the depth limits, the Article 4 direction and the validation list for a house

Hillingdon's rear-extension numbers, in Local Plan Part 2

Hillingdon decides householder applications against its Local Plan Part 2: Development Management Policies, which the council's local plan page says was adopted at Full Council on 16 January 2020. The policies document puts extensions in Policy DMHD 1, which gives figures. Our Hillingdon house extension drawings page covers the drawing set.

For a single-storey rear extension DMHD 1 B says terraced or semi-detached houses on plots of 5 metres or less “should not exceed 3.3 metres in depth or 3.6 metres where the plot width is 5 metres or more”, and a detached house on a plot of 5 metres or more should not exceed 4.0 metres. Flat roofs should not exceed 3.0 metres in height and pitched roofs 3.4 metres, measured from ground level.

The two-storey test is a line on your drawing. A two storey extension “should not extend into an area provided by a 45-degree line of sight drawn from the centre of the nearest ground or first floor habitable room window of an adjacent property”, and should have no openings that overlook houses at less than 21 metres. At the side, two storey extensions should be set in a minimum of 1 metre from the boundary, and in the Copse Wood and Gatehill estates at least 1.5 metres.

What the February 2024 validation checklist asks for a house

Hillingdon's Local Planning Validation Checklist is dated February 2024 on its cover. It lists the national requirements and then the local ones for each type of application, and the householder page is short. Nationally it asks for the form, a location plan at 1:1250 or 1:2500, existing and proposed block plans at 1:500, floor plans and elevations at 1:50 or 1:100, the ownership certificate and the fee.

The local rows for a householder are a basement impact assessment or structural survey for any basement, the CIL additional information form, data required by the Greater London Authority Data Standard, a flood risk assessment in Flood Zones 2 and 3a, an Environment Agency flood risk matrix for a basement or ground-floor extension in Zone 2 or 3, a heritage statement, a tree survey and vehicular parking and access details. The notes add two practical rules: the location plan “must not be sourced from Land Registry”, and an application that fails checks is given 28 days to supply what is missing.

The parking row ties to policy: DMHD 1 A asks that adequate off-street parking is retained, and DMHD 1 F says a new impermeable driveway of more than five square metres needs planning permission. At least 25% of the front garden must be kept. Our location and block plans page covers the plans the list names.

Conservation areas, local character areas and listed buildings

The council's conservation areas page says there are 31 designated conservation areas in the borough. The checklist asks for a heritage statement on a householder application “if in Conservation Area, or relates to a Listed Building or Locally Listed Building”, and it says the statement should show the Historic Environment Record has been consulted.

The plan adds stricter drawing rules for these places. In conservation areas and Areas of Special Local Character, flat-roofed single-storey extensions are expected to have a parapet, full-width two storey rear extensions are not considered acceptable in designated areas, and single-storey side extensions may be required to be set back. Policy DMHB 5 asks extensions in Areas of Special Local Character to be subservient and to leave space for landscaping. Our heritage statement page covers the document.

Building regulations, party walls and daylight

Hillingdon's building control page covers applying for building control approval, searching existing applications and requesting site inspections. Planning permission and building regulations are separate approvals, so a planning decision does not replace a building control application. Our building regulations reports guide sorts the reports by project, and the building regulations drawings page covers the set that goes to building control.

A daylight and sunlight report is not a householder row. The checklist describes it for developments that could reduce the daylight or sunlight to adjacent occupiers, using the Building Research Establishment guidance, so it appears for larger schemes. For a house the neighbour test is the 45-degree line above. The Party Wall etc. Act 1996 is national law that runs beside planning, and our party wall services guide explains the notices to neighbours.