Single-storey, double-storey, rear and side extension drawings for Spelthorne homes — measured to Spelthorne Borough Council's design guidance, delivered in days and revised free until your decision, with a free approval-odds check before you commit.
Spelthorne Borough Council granted 90% of the householder planning decisions it made in its latest published year — 3 points above the 87% England-wide householder average. The borough is flat and low-lying, so severe Thames flood risk — with functional floodplain in Flood Zone 3b an absolute constraint — dominates where and how development can go, which is where a policy-literate drawing pack earns its keep. Its dominant Victorian (1837–1901), Edwardian (1901–1910), interwar (1918–1939) and postwar (1945–1970) housing stock sets the design brief on most streets.
Class A and Class B set the thresholds — a rear dormer to 40m³ on a terrace or 50m³ on a semi or detached, and a single-storey rear extension to 3m on a terrace or 4m on a detached house — beyond which Spelthorne Borough Council needs a full application. Spelthorne carries at least one Article 4 direction, and conservation areas including Staines, Laleham and Lower Sunbury remove those rights outright, so we confirm your exact address before a line is drawn. A validated householder application in Spelthorne is determined against an 8-week statutory target.
Staines-upon-Thames (the main town with Victorian, Edwardian and twentieth-century housing and a riverside conservation area), Ashford (largely interwar and postwar suburban semis and detached commuter housing), Sunbury-on-Thames (riverside period and suburban housing with the Lower Sunbury conservation area along the Thames), Shepperton (a historic Church Square village core and riverside studio-town character), Laleham (a small Thames-side conservation village of period and detached riverside houses) and Stanwell (mixed postwar estate housing near Heathrow with its own conservation area) — these are the Spelthorne pockets our drawings cover most. Heritage designations here include Staines, Laleham, Lower Sunbury, Shepperton, Lower Halliford and Stanwell. Spelthorne Borough Council weighs each proposal against the Spelthorne Local Plan 2024–2039 (adopted March 2026), where Metropolitan Green Belt covers much of the undeveloped borough, with only weakly-performing parcels considered for release. Converted flats and maisonettes are common around Staines and Ashford, and none of them hold householder permitted-development rights.. On roofs the borough is hipped roofs on the interwar and postwar semis and dual-pitch tiled roofs on the riverside period houses, over interwar and postwar semi-detached and detached suburban housing across Ashford, Sunbury and Stanwell, Victorian, Edwardian and twentieth-century housing around Staines-upon-Thames, riverside period and detached villas along the Thames at Laleham, Shepperton and Lower Sunbury and historic village and church cores.
Spelthorne homes come in a handful of recurring shapes, and each one points to a different extension. The borough is built largely from interwar and postwar semi-detached and detached suburban housing across Ashford, Sunbury and Stanwell, Victorian, Edwardian and twentieth-century housing around Staines-upon-Thames, riverside period and detached villas along the Thames at Laleham, Shepperton and Lower Sunbury and historic village and church cores, so a Victorian terrace usually wants a rear or side-return infill, while an interwar semi has room for a wider single-storey wrap or a two-storey side addition. Spelthorne Borough Council judges every one of them against the Spelthorne Local Plan 2024–2039 (adopted March 2026), weighing footprint, height and the impact on the house next door before it looks at the elevations.
That is why the drawings decide the outcome. We set the extension depth against the permitted-development limits precisely, keep the eaves and ridge within the allowances, and plot the 45-degree daylight lines to the neighbours' windows so the case officer can see the amenity test is passed. The borough is flat and low-lying, so severe Thames flood risk — with functional floodplain in Flood Zone 3b an absolute constraint — dominates where and how development can go, so we design around it from the first sketch rather than discover it at validation.
Spelthorne also protects whole streets — Staines, Laleham, Lower Sunbury, Shepperton, Lower Halliford and Stanwell among them. Spelthorne has brought in a borough-wide Article 4 direction, phased in across all wards during 2025 and 2026, removing the permitted right to convert a dwelling into a small HMO so that these conversions now need planning permission everywhere in the borough. On designated land the larger-home extension route and most side extensions stop being permitted development, so we confirm your address against those layers before drawing a line.
Plenty of Spelthorne extensions are permitted development and need no planning application — a single-storey rear extension within the depth and height limits is the common case. You will normally need to apply to Spelthorne Borough Council if any of these apply:
We draw the footprint, the ridge and eaves heights and the neighbours' daylight on the page — the relationships Spelthorne Borough Council's officers weigh first — and submit a validation-complete pack, whether that is a lawful development certificate, a prior-approval notification or a full householder application.
Below is Spelthorne Borough Council's real householder decision record, drawn from official planning statistics and refreshed as new data lands. Spelthorne grants a little above the national average of applications, with Thames flood risk and green-belt containment the constraints that shape most larger schemes. A complete, policy-literate extension pack anticipates those pressure points before submission, which is why professionally drawn applications are decided faster and refused less often than DIY ones.
Source: MHCLG planning application statistics (householder decisions, England, 1 April 2025 - 31 March 2026). Compare every borough on our London approval-rate league table.
Tell us about your project and get a fixed, no-obligation quote back within one working day. If you don't need planning permission at all, we'll tell you that too — for free.
Across Staines-upon-Thames, Ashford and Sunbury-on-Thames, the extension that lands most often is the single-storey rear addition — a glazed kitchen-diner across the back of the house, kept within the permitted-development depth or taken to a full application where the ground floor wants more. On the borough's interwar and postwar semi-detached and detached suburban housing across ashford, sunbury and stanwell, a side-return infill frequently pairs with it to square off the plan; on wider historic village and church cores, a two-storey side or rear extension can add a bedroom above without swallowing the garden.
Metropolitan Green Belt covers much of the undeveloped borough, with only weakly-performing parcels considered for release. We size the extension to the amenity and daylight tests, match the roof and materials to the host house, and keep enough garden to satisfy Spelthorne Borough Council's space standards — so the scheme answers the borough's questions before an objection can raise them. Where permitted-development rights are used up or removed, we prepare the householder application to the council's extension design guidance instead.
We draw extensions on every street in the borough. A few of the neighbourhoods where Spelthorne projects come up most often:
Extension drawings for Staines-upon-Thames's the main town with Victorian, Edwardian and twentieth-century housing and a riverside conservation area — footprint-checked, daylight-tested and drawn to Spelthorne Borough Council's guidance.
Extension drawings for Ashford's largely interwar and postwar suburban semis and detached commuter housing — footprint-checked, daylight-tested and drawn to Spelthorne Borough Council's guidance.
Extension drawings for Sunbury-on-Thames's riverside period and suburban housing with the Lower Sunbury conservation area along the Thames — footprint-checked, daylight-tested and drawn to Spelthorne Borough Council's guidance.
Extension drawings for Shepperton's a historic Church Square village core and riverside studio-town character — footprint-checked, daylight-tested and drawn to Spelthorne Borough Council's guidance.
Extension drawings for Laleham's a small Thames-side conservation village of period and detached riverside houses — footprint-checked, daylight-tested and drawn to Spelthorne Borough Council's guidance.
Extension drawings for Stanwell's mixed postwar estate housing near Heathrow with its own conservation area — footprint-checked, daylight-tested and drawn to Spelthorne Borough Council's guidance.
The right extension in Spelthorne depends on your house type and how much garden you can give up. This is how the main options compare on planning route and what they add.
| Extension type | Permitted development? | What it adds | What Spelthorne Borough Council checks |
|---|---|---|---|
| Single-storey rear | Often, within 3m/4m depth (6m/8m via prior approval) | Bigger kitchen-diner across the back | Depth, height, neighbour daylight (45°) |
| Side-return infill | Sometimes, if within width and height limits | Squares off an L-shaped ground floor | Width vs the original house, glazing to boundary |
| Two-storey rear/side | No — full application | Extra bedroom or bathroom above | Bulk, overlooking, 7m rear-boundary gap |
| Wraparound (rear + side) | No — full application | Whole-width open-plan ground floor | Combined footprint and garden retained |
Route depends on your street — conservation areas such as Staines and Laleham and Article 4 directions can remove permitted-development rights.
A fixed process built around how Spelthorne Borough Council validates and decides householder extension applications — most drawings are submission-ready within seven days of survey.
Tell us your Spelthorne postcode and house type. We confirm your conservation and Article 4 status, how much permitted-development depth you have left, and score your odds against live Spelthorne Borough Council decisions.
We measure the existing footprint, floor and eaves levels, boundary distances and the neighbours' window positions — the numbers the depth limits and daylight tests depend on.
Chartered designers develop the single-storey, two-storey or side extension to your brief, drawn inside the permitted-development limits or to Spelthorne Borough Council's extension design guidance.
We submit the certificate, prior-approval notice or application, manage validation and case-officer queries, and revise the drawings free until Spelthorne Borough Council issues its decision.
Not always. A single-storey rear extension up to 3 metres deep on a terrace or semi, or 4 metres on a detached house, and no higher than 4 metres, is usually permitted development. In Spelthorne you will need to apply to Spelthorne Borough Council for two-storey extensions, side extensions wider than half the house, anything forward of the front wall, deeper rear extensions under the larger-home prior-approval route, and any extension in a conservation area such as Staines and Laleham.
Standard permitted development allows 3 metres on a terraced or semi-detached house and 4 metres on a detached one. The larger-home extension scheme can double that to 6 or 8 metres, but it needs a prior-approval notification to Spelthorne Borough Council and a neighbour-consultation period, and it does not apply on designated land such as Spelthorne's conservation areas. We confirm which route your property qualifies for before drawing.
Two-storey and double-storey extensions almost always need a full householder application to Spelthorne Borough Council, because they fall outside permitted development on most homes. The council looks closely at bulk, overlooking of neighbours and the 7-metre gap a two-storey rear extension must keep from the rear boundary. We design to those tests and show the daylight and privacy angles on the drawings.
A householder planning application in Spelthorne runs to a statutory eight-week target, a larger-home prior-approval notification to around six weeks including the neighbour-consultation period, and a lawful development certificate to eight weeks. Incomplete submissions stall at validation, so we submit a complete pack and manage officer queries to keep the decision on schedule. Spelthorne Borough Council is the decision-maker.
Yes — planning permission and building regulations are separate consents, and almost every extension needs both. Planning governs whether you can build it; building control governs how it is built, covering structure, insulation, drainage and fire safety. We prepare the building-regulations drawings alongside the planning set so Spelthorne Borough Council's building control or an approved inspector can sign the work off.
Every house and brief is different, so we price each Spelthorne extension individually and send a fixed, no-obligation quote back within one working day. It covers the full drawing pack with free revisions until Spelthorne Borough Council approves, and we tell you upfront whether your extension qualifies as permitted development. Call 020 7864 7245 to get started.
Answer five quick questions and get a free planning score for your exact address — instantly. Then, if you want the full picture, unlock the detailed analysis: your council's live approval rates, local precedents, constraints on your street and a step-by-step route to permission.
Same fixed quotes, same fast drawings — wherever your project is.