Hounslow planning guide: the Residential Extension Guidelines and what the council asks you to submit

Hounslow's Local Plan and the Residential Extension Guidelines

The Hounslow Local Plan (2015) is, in the council's words, the main local policy framework for development in the borough, and the Residential Extension Guidelines were adopted as a Supplementary Planning Document on 20 December 2017 to expand it. The guidelines list Policy SC7, Residential extensions and alterations, alongside CC1 (context and character), CC2 (urban design and architecture) and CC4 (heritage) as the policies that apply. The council's local plan page also lists the examination documents for a Local Plan review, so check it for anything newer than the 2015 plan. The council's own guidelines page describes the purpose: clear advice on what the council considers acceptable forms of extension.

The preface is candid about how the document works. Because every property differs, “a proposal that follows the letter of the Guidelines may not always be acceptable or that one that does not may sometimes be acceptable due to the circumstances of the site”, though a proposal that does not meet them runs “a risk that it will be refused”. Our Hounslow planning permission page and house extension drawings in Hounslow cover the drawing sets.

What the checklist and the application page ask you to send

Hounslow's householder checklist is the householder planning application checklist. The document says it went through six weeks of public consultation between 14 October and 29 November 2019 and shows no later date, while also saying a local list must be reviewed every two years. Treat it as the base and read the council's apply for planning permission page beside it, which carries later requirements.

The checklist's detail is specific. The location plan, at 1:1250 or 1:2500, “must not be sourced from Land Registry or the London Borough of Hounslow”. The block plan at 1:500 shows boundaries, existing structures, landscaping and fences, parking and waste storage, utility manholes, a north point and a scale bar. Elevations at 1:50 or 1:100 show the relationship to an adjoining building in close proximity, with the positions of openings, parapets and levels, and include blank elevations for clarity. Floor plans, roof plans and sections are at 1:50 or 1:100, and sections give existing site levels and finished floor levels. An email address for the applicant or agent must be on the form, because the council writes by email when an application is invalid.

The apply page adds a fire-safety requirement that a householder extension must meet. For a non-major application to be validated, the council requires a site plan showing a dedicated unobstructed area for storing fire equipment, a site plan showing a dedicated unobstructed area for evacuation, and a statement confirming the requirements of London Plan policy D12a have been met. Our fire safety statement page covers the statement, and the council's naming guide and a request for current site photographs also sit on that page.

Heritage: 28 conservation areas in the guidelines and two Article 4 areas

The guidelines say there are 28 conservation areas in Hounslow, a count from the 2017 document, so confirm yours on the council's map. Their conservation rules are tight: new extensions “should never dominate”, an original rear projection such as a two-storey outrigger “must be preserved”, wrap-around proposals “will generally be refused”, and two-storey and first-floor rear extensions are normally refused where clearly visible from the public realm or harmful to the area. In some areas painting render or brickwork, or cladding, needs planning permission.

The council's Article 4 directions page lists Article 4(2) directions for the Bedford Park and Gunnersbury conservation areas, alongside a borough-wide direction on small HMOs and a 2025 direction on changes that create new dwellings in specified centres and employment areas. A heritage statement supports any listed building proposal and any change that affects one's setting, and a design and access statement is asked in a conservation area when the new floor space is 100sqm or more. Our heritage statement page covers the document, and the Hounslow prior approval extension page covers the larger home extension route.

Party walls, basements and construction method statements

The guidelines treat party wall agreements and land ownership as civil matters “not material to consideration of a planning application”, and add that a basement below ground may still need a Party Wall Agreement. The notices are national law under the Party Wall etc. Act 1996, and our party wall services guide explains them.

For a basement, the checklist lists a Design and Construction Method Statement when the proposal involves excavation or extension of a basement, and the guidelines say that where the council allows one, a Construction Method Statement certified by a suitably qualified engineer is required by condition, covering excavation, temporary works and the impact on neighbouring land. They also say a basement should be no deeper than one subterranean floor and should not extend beyond the main front or side walls, and set modest lightwell sizes. A basement feasibility visit comes before drawings. Where a tree is protected or stands in a conservation area, the checklist asks for a tree survey, covered by our tree survey for planning page.