House
extensions
in St George's Hill, KT13
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Extensions to detached houses on St George's Hill, sized against the Design Code's plot ratio, drawn to each house's own roof and materials, and set out around the trees on and beside the plot.
Council documents describe large detached houses on St George's Hill, set in very generous wooded plots, and the council's 2012 description of the estate noted demand for large extensions to them. On plots of this size, we start an extension with three questions: how the addition sits on the house, how much of the plot the buildings end up covering, and what happens to the roots of the trees nearby.
Each of those questions has a council document behind it, and the estate has its own residents' association whose requirements you should check with it directly. We work through both before the first drawing is issued.
How much of a St George's Hill plot an extension can cover
The Design Code records residents describing Weybridge's “gated neighbourhoods with large detached properties with some in private estates, including St Georges Hill”. The 2012 guide, which we use only as description since the code replaced it for applications submitted after 6 January 2025, recorded very generous wooded plots and demand for large extensions. The code now measures coverage as a plot ratio, the building footprint divided by the area of the site, and asks householder extensions to keep within the range for their area type where possible. Which type a plot is in is shown on the code's map of area types, which we read for your address; for the Gated type the indicative range is 0.1 to 0.2.
An application must state the proposed plot ratio and the ratio of every neighbouring plot that shares a boundary, and a householder application must include the Design Code Checklist. The code's own examples of householder work run from single and two-storey extensions to conservatories, raised patios, outbuildings and porches.
We measure the footprint of the house and every outbuilding from the survey, take neighbouring footprints from mapping and what can be seen from the plot, and show the ratios on the drawings, so the figure is settled before the design is.
Sources: Elmbridge Borough Council: Elmbridge Design Code 2024 (SPD); Elmbridge Borough Council: Design Code SPD page; Elmbridge Borough Council: Companion guide - Weybridge (Design and Character SPD 2012)
Rear extensions under permitted development on the hill
Class A permitted development covers the enlargement, improvement or other alteration of a house within set limits. For a detached house, a single-storey rear extension may reach no more than 4 metres beyond the rear wall of the original house and no more than 4 metres in height. Where the house is not on Article 2(3) land or a site of special scientific interest, that depth can go to 8 metres through prior approval: the developer first gives the local planning authority the information the order lists, and if the owner or occupier of an adjoining property objects, the authority's prior approval is needed on the effect on that neighbour's amenity. Work starts only once the authority has given its approval, said none is needed or let the deadline in the order pass.
Under Class A, a rear extension of more than one storey is held to 3 metres beyond the original rear wall and must stay 7 metres from the boundary opposite that wall. Nothing may project beyond the principal elevation. A side extension may not exceed 4 metres in height, have more than one storey or be wider than half the original house. Balconies and raised platforms fall outside Class A, and exterior materials must look similar to the existing house.
Two further checks shape permitted development on the hill. For a house built on or after 1 July 1948, 'original' means as it was built, so a replacement house is measured from its own first form rather than from the house it replaced. And the council says any permitted development scheme that may affect protected trees, roots included, needs its permission.
The council's pre-application service does not cover permitted development, but a lawful development certificate confirms in writing whether a proposal needs planning permission. We read the house's planning history before relying on permitted development, and the estate's own requirements should be checked with the residents' association whichever route applies.
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); Elmbridge Borough Council: Check if you need planning permission (householders); legislation.gov.uk (The National Archives): GPDO 2015, Article 2 (Interpretation) - defines 'article 2(3) land'; Elmbridge Borough Council: Companion guide - Weybridge (Design and Character SPD 2012); Elmbridge Borough Council: Building near a tree; Elmbridge Borough Council: Get advice before applying for planning permission (householders)
Designing an addition to a large detached house
Where an application is needed, it is decided by Elmbridge Borough Council until 31 March 2027; East Surrey Council from 1 April 2027, and the Design Code's extension guidance applies. A fully integrated extension is usually only successful where it leaves the house's symmetry intact, which the code says is possible on a detached house. The roof should follow the existing one in scale, design and pitch; a house with a pitched roof should not be given flat-roofed extensions, though that may not apply to a single-storey rear addition to a house of two or more storeys. On a two-storey extension the eaves should line through and sit no higher than the existing ones.
Materials and detailing should match the house in design, colour and texture. Above ground floor, an extension should keep at least 1 metre from the boundary. Two-storey rear extensions must be very carefully sited, and a flat roof used as a balcony or terrace is not usually acceptable unless it is well screened or sits within a substantial plot where nobody would be overlooked.
The 2012 guide found the houses largely set back from the road behind vegetation. Where a front addition is considered, the code's guidance for streets with setbacks and frequent variations instead of a clear building line is that neighbouring frontages set the zone for the new one.
We draw an extension to the house's own proportions first and to the code second, then test the elevations from the road and from each neighbouring garden before the drawings go to the council.
Sources: Surrey councils (Future Surrey hub, linked from Elmbridge home page): East Surrey Council (Future Surrey LGR hub); Elmbridge Borough Council: Elmbridge Design Code 2024 (SPD); Elmbridge Borough Council: Companion guide - Weybridge (Design and Character SPD 2012)
Trees, roots and sand beneath an extension
Where trees on the site, or on land next to it, could influence or be affected by the work, the council may ask for a tree survey with root protection areas, a tree retention and removal plan, a tree protection plan and an arboricultural impact assessment, and sometimes an arboricultural method statement and existing and proposed levels. Without information to the British Standard, it says, an application is likely to be invalidated or refused.
The council's flood assessment describes sandy ground: a small area of sand and gravel at St Georges Hill, isolated patches of Camberley Sand and Windlesham Formation found mainly around the hill, and Bagshot Formation sand beneath, with clay laminations, silt layers and flint pebble beds. The Design Code asks drainage proposals to show no increase in surface water run-off.
Towards the south of the hill, the Development Management Plan's scheduled multivallate fort, also a County Site of Archaeological Importance, needs checking. Scheduled monuments are shown on the Policies Map, and the plan notes that the county site often extends beyond the scheduled boundary, so we ask about its extent before planning any digging.
We commission the arboricultural survey before the layout is fixed, then dig trial pits clear of root zones so the engineer can choose foundations that suit both the soil and the trees, considering piles and ground beams where roots run under the footprint.
Sources: Elmbridge Borough Council: Building near a tree; Elmbridge Borough Council: Level 1 Strategic Flood Risk Assessment, April 2024 (AECOM); Elmbridge Borough Council: Elmbridge Design Code 2024 (SPD); Elmbridge Borough Council: Development Management Plan (April 2015); Elmbridge Borough Council: Companion guide - Weybridge (Design and Character SPD 2012)
Building regulations and site set-up for an extension
Building control on the hill is Elmbridge Building Control Services (EBCS), for Elmbridge Borough Council, until 31 March 2027, and from 1 April 2027 the provider named by East Surrey Council. The council's building control page names extending a home as one reason approval may be needed, and Building Regulations apply regardless of the planning position.
Before set-up, check the estate's own requirements with St.George's Hill Residents Association Limited. We then plan deliveries, storage and parking around the association's answer, put tree protection fencing in place before any machine arrives, and keep the drive, verges and planting protected until handover.
The build follows the approved drawings and engineer's details, with each building control inspection booked as the work reaches it, and finishes with a handover file holding the completion certificate, drawings and product information.
Outside St George's Hill, 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: Elmbridge Borough Council: Building control; Surrey councils (Future Surrey hub, linked from Elmbridge home page): East Surrey Council (Future Surrey LGR hub); Companies House: ST.GEORGE'S HILL RESIDENTS ASSOCIATION LIMITED (00267063); Hampstead Renovations: Holland Avenue, Wimbledon SW20 case study
House Extensions in St George's Hill: Questions
Is my St George's Hill house in the Green Belt, and how big can the extension be?
The Green Belt boundary is defined on the council's Policies Map, and we check it for your house and garden; if any part of the site lies inside it, the borough's Green Belt test on our Elmbridge page applies. On size, the Design Code asks householder extensions to keep within the plot ratio range for their area type where possible, gives the Gated area type an indicative range of 0.1 to 0.2, and expects the ratios of neighbouring plots to be stated alongside yours. Its map of area types shows which type your plot is in, and we read it before relying on any range.
Can I build a rear extension in St George's Hill under permitted development?
For a detached house, Class A allows a single-storey rear extension up to 4 metres beyond the original rear wall and 4 metres high, or up to 8 metres through the prior approval procedure where the house is on neither Article 2(3) land nor a site of special scientific interest. Any scheme that may affect protected trees or their roots needs the council's permission. We read the planning history before relying on permitted development, the council can confirm a proposal through a lawful development certificate, and the estate's own requirements should be checked with the residents' association.
Does Article 2(3) land change what I can build in St George's Hill?
Article 2(3) land is land within a conservation area, an area of outstanding natural beauty, an area specified under section 41(3) of the Wildlife and Countryside Act 1981, the Broads, a National Park or a World Heritage Site. On it, Class A rules out side extensions, cladding in materials such as render, timber or tiles, and any rear extension of more than one storey; the 8 metre single-storey route is not available either. St George's Hill is not among the conservation areas the Design Code names in Weybridge, and we confirm the position for your address on the council's My Neighbourhood service before relying on any of these limits.
How does the flood zone affect an extension in St George's Hill?
The council's flood assessment describes St George's Hill as higher ground at 75m AOD, with the river floodplain along the low western edge of the Weybridge Settlement Area. Check your plot on the Environment Agency's flood map for planning, which says whether an application needs a flood risk assessment; for a simple, low-risk development such as a house extension, the Environment Agency says you may be able to prepare it yourself. Drainage is still designed in: the Design Code asks proposals to show no increase in surface water run-off.
Who checks the building regulations on an extension in St George's Hill?
Elmbridge Building Control Services (EBCS), for Elmbridge Borough Council, until 31 March 2027, and from 1 April 2027 the provider named by East Surrey Council. Extending a home is among the work the council lists as possibly needing approval, and its officers check the work against the Building Regulations. We make the application, book each inspection and hand over the completion certificate.
What do you need from me before visiting a St George's Hill property about an extension?
The address, a short note of what you want to add, any existing drawings or survey of the house, decision notices for past applications, a tree report if there is one, and anything the residents' association has told you in writing. We arrange the measured and arboricultural surveys ourselves after the free feasibility visit.
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Completed renovation project example
