House
extensions
in Virginia Water, GU25

The council's flood study gives the Virginia Water ward as 87% Green Belt and 13% Urban Area, and the neighbourhood plan's screening report describes the area as washed over by the Green Belt in large parts, but not entirely.

On a Green Belt plot, Local Plan Policy EE14 says the extension of a building is not inappropriate development provided that it does not result in disproportionate additions over and above the size of the original building. The original building is the house as it stood on 1 July 1948, or as first built if that was later.

The council weighs the planning history since 1 July 1948, including work done under permitted development, and considers garages, other outbuildings, walls, gates and hardstanding alongside the house itself.

So the first task is to establish what has already been added since 1948. The full wording of the borough's test is on our Runnymede page; on your plot we gather every past approval and measure the earlier additions before drawing anything new.

Sources: Runnymede Borough Council: Runnymede 2030 Strategic Flood Risk Assessment (Level 1, January 2018); Runnymede Borough Council: Virginia Water Neighbourhood Plan SEA/HRA Screening Report; Runnymede Borough Council: Runnymede 2030 Local Plan (adopted document, PDF)

Within the other limits of Class A of the national permitted development order, a single-storey rear extension may reach 4 metres beyond the original rear wall of a detached house, or 3 metres for any other house.

Away from article 2(3) land and sites of special scientific interest, the order stretches that to 8 metres for a detached house and 6 metres for others, but only through the order's notification procedure, which requires details of the proposal to be given to the council before work begins.

An addition of more than one storey may not reach more than 3 metres beyond the rear wall. A side extension is limited to one storey and to half the width of the original house, and buildings other than the original house may not cover more than half of the property's curtilage.

On a Green Belt plot, a permitted development extension still goes into the planning history the council reads later, so we plan the next addition with that total in mind.

Sources: legislation.gov.uk (The National Archives): The Town and Country Planning (General Permitted Development) (England) Order 2015, Schedule 2, Part 1 (development within the curtilage of a dwellinghouse) - latest available (revised); Runnymede Borough Council: Runnymede 2030 Local Plan (adopted document, PDF)

Policy VW1 asks new work to relate to the existing pattern of streets, plot sizes and spaces between buildings, and to keep trees, hedgerows and green spaces where it can.

In Trumps Green the code asks proposals to generally adhere to the uniform plot shapes and strong building lines, to keep and bolster frontage trees and hedges on roads such as Crown Road and Knowle Grove, and to protect the clusters of mature trees in the back gardens of Trumps Green Avenue.

Along Stroude Road and Sandhills Lane buildings should front the main road and respect the strong building lines, while around Virginia Park and St Ann's the existing pattern of built form and architectural style is to be retained, with some scope for innovation and other change.

The council's Design SPD adds householder guidance. An extension should be smaller and lower than the original house, with its roof pitch and eaves matching. As a guide, a two-storey rear extension should stay within a 45 degree line taken from the centre of the neighbouring house's main habitable-room window, and a two-storey side extension should in most cases keep at least 1 metre from the side boundary. The SPD treats these figures as guides, with each case judged on its merits.

Sources: Runnymede Borough Council: Virginia Water Neighbourhood Plan 2024-2035, adoption version, with the Virginia Water Design Code (Appendix 1); Runnymede Borough Council: Runnymede Design Supplementary Planning Document (adopted July 2021)

Under Policy EE13, any development proposed in Flood Zone 2 or 3, minor development included, needs a site-specific flood risk assessment. The Environment Agency notes that for a simple, low-risk job such as a house extension you may be able to prepare it yourself.

Inside the urban area the flood zones reach some rear gardens in Keepers Walk and Nun's Walk, and the flood study marks a higher surface water risk along parts of Oak Tree Close, Knowle Grove and Trumpsgreen Road.

The neighbourhood plan expects sustainable drainage where it is required, and the flood study lists Virginia Water among the areas of freely draining soils. We still dig a trial pit and test percolation before a soakaway is shown on any drawing.

Building near or on a shared boundary means telling the neighbours first, and party walls include garden walls, though not wooden fences. Building control will not settle party wall matters, which sit with civil law.

A garden annex for a relative raises one more question: the council's heathland SPD considers residential annexes individually, so we raise it before design starts.

The structural engineer designs the foundations from the trial pits and the steel from the opening sizes, and we agree with neighbours where scaffold, skips and deliveries will stand before the first trench is dug.

Outside Virginia Water, and in London rather than Surrey: Holland Avenue, Wimbledon SW20. That completed project of ours combined a loft conversion, a double-storey extension to the rear and side, and a whole-home refurbishment, as its case study describes.

Sources: Runnymede Borough Council: Runnymede 2030 Local Plan (adopted document, PDF); Environment Agency (gov.uk service): Flood map for planning (Get flood risk information for planning in England); Runnymede Borough Council: Runnymede 2030 Strategic Flood Risk Assessment (Level 1, January 2018); Runnymede Borough Council: Virginia Water Neighbourhood Plan 2024-2035, adoption version, with the Virginia Water Design Code (Appendix 1); GOV.UK: Party walls and building work; Runnymede Borough Council: About building control - What is building control; Runnymede Borough Council: Thames Basin Heaths Special Protection Area SPD; Hampstead Renovations: Holland Avenue, Wimbledon SW20 case study