Croydon planning guide: what the May 2026 Local Validation List asks of a house extension

The Local Plan 2018 policy that governs a Croydon extension

Croydon decides applications against the Croydon Local Plan 2018, dated 27 February 2018 on its cover, read with the London Plan. The council's local plan page calls it the key strategic policy for planning and development in the borough. The plan carries a table of which policies probably apply to which kind of scheme, and for a household extension it names one: Policy DM10, Design and character. Our Croydon planning permission page covers the drawing set for an application here.

Under DM10.1 a proposal should respect “the development pattern, layout and siting”, “the scale, height, massing, and density” and “the appearance, existing materials and built and natural features of the surrounding area”. The same policy adds that where an extension is proposed, “adherence to Supplementary Planning Document 2 Residential Extensions and Alterations or equivalent will be encouraged”.

DM10.6 is the neighbour test. The council will support development that ensures “the amenity of the occupiers of adjoining buildings are protected” and that does not “result in significant loss of existing sunlight or daylight levels of adjoining occupiers”. Those words are why the elevations and block plan need to show where the neighbours' windows and rear gardens sit.

Flood risk: a statement even when you are nowhere near a river

The list says “all applications require a Flood Risk Assessment (FRA), even if not in areas at risk of flooding”, to show the scheme does not add to flood risk. For a householder extension the scale is modest: the list says it “may require a brief statement, a search of online flood risk maps to identify risks, and proportionate measures such as a water butt or permeable paving”. Local Plan Policy DM25.3 backs this with the rule that sustainable drainage systems are required in all development.

A basement raises the bar. Where a basement is proposed in an area at risk of groundwater flooding, the FRA should include a basement impact assessment covering aquifers and watercourses, effects on drainage and neighbours, and ongoing maintenance. A basement also needs a topographical survey with spot heights and contours. Our flood risk assessment page and drainage statement page cover the documents, and a planning constraints report shows the flood zone for your address first.

Daylight and sunlight: the list asks majors, the policy asks everyone

The daylight and sunlight assessment row has a threshold of “Majors”, so a household extension does not need one to be valid. That does not make the question go away. DM10.6 still tests loss of daylight to adjoining occupiers, and a case officer who sees a deep rear extension beside a close ground-floor window can raise it during the application.

A daylight and sunlight report is therefore evidence you may choose to put in early, not a validation item. Our specialist partner prepares it from the drawings, using the method in the Building Research Establishment guidance the list names.

Party walls, basements and construction logistics

The Party Wall etc. Act 1996 is national law that runs beside planning, and the list's warning about ownership certificates on party-wall extensions is a separate point from the Act's notices. Our party wall services guide explains the notices to neighbours.

Croydon's list asks for a construction management or logistics scoping note on larger schemes, and adds that one “may also be requested during the course of an application for smaller minor developments that are likely to cause nuisance or disturbance to residential amenity, or hazard and obstruction to the public highway”. A basement under a terrace on a narrow road is the obvious case. The note covers phasing, hours, vehicles, dust and a risk assessment. A basement feasibility visit comes before drawings, and the construction management plan page explains the note.

Fire, biodiversity and trees: three more rows to check

The fire row applies to “all applications”: a statement setting out the fire strategy, or an exception statement explaining why one is not needed, following the London Plan's fire safety guidance. For a simple house extension the exception note is the usual route, and our fire safety statement page covers both. Householders are not required to supply an Application Inventory, though the list warns that a complex application with several documents may be made invalid if it is unclear whether the requirements were met, so a short cover letter is cheap insurance.

On biodiversity net gain, the list asks for a statement of the exemption relied on when a scheme is exempt, which can sit in the application form or the cover letter. Where trees stand on or beside the site, the list asks for a tree survey and protection details from a suitably qualified arboriculturist to BS5837:2012, and our tree survey for planning page covers that.