Two-storey extension drawings for Spelthorne homes — bedroom above, living space below, drawn against the 3-metre projection and 7-metre boundary rules and to Spelthorne Borough Council's design guidance, delivered in days and revised free until your decision.
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.
Adding at first floor changes the question the case officer asks. A single-storey extension is judged mostly on daylight and garden loss; a two-storey extension is judged on overlooking, bulk against the neighbouring roofline, and whether it reads as part of the house or bolted onto it. Spelthorne is largely 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, and hipped roofs on the interwar and postwar semis and dual-pitch tiled roofs on the riverside period houses set what a matching roof actually means here.
The permitted-development route exists but is narrow: 3 metres of rear projection, a 7-metre stand-off from the rear boundary, eaves and ridge no higher than the original, and side-facing upper windows obscure-glazed and non-opening below 1.7 metres above floor level. Most two-storey schemes fail one of those, usually the 7-metre boundary rule on a shorter garden, and go in as a full application instead. We establish which route applies before designing, because it changes the drawing set.
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. 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.
Some two-storey rear extensions are permitted development. You will need a full application to Spelthorne Borough Council if any of these apply:
We set the projection and boundary distance on the site plan, prove the roof-pitch match on the elevations, and specify obscure glazing on the side windows — the three things Spelthorne Borough Council checks first — then submit a validation-complete pack.
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. Two-storey schemes attract more neighbour comment than any other householder work, so the overlooking and daylight case has to be made on the drawings.
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 schemes that succeed set the first floor back from the ground floor, keep the ridge below the original, and treat the flank wall as blank or obscure-glazed. On interwar and postwar semi-detached and detached suburban housing across ashford, sunbury and stanwell, matching the eaves line matters more than matching the brick: an extension that carries the existing eaves through reads as original even in a different material.
Metropolitan Green Belt covers much of the undeveloped borough, with only weakly-performing parcels considered for release. We draw the 45-degree daylight test from the neighbour's nearest habitable window, show the window positions in section, and set out the steel and foundation implications early — a two-storey extension changes the load path, so the structural design and the planning design have to be developed together rather than in sequence.
We draw two-storey extensions across Spelthorne. A few of the areas where they come up most often:
Two storey extension drawings for Staines-upon-Thames — the main town with Victorian, Edwardian and twentieth-century housing and a riverside conservation area — dimensioned against the 3m and 7m limits and drawn to Spelthorne Borough Council's guidance.
Two storey extension drawings for Ashford — largely interwar and postwar suburban semis and detached commuter housing — dimensioned against the 3m and 7m limits and drawn to Spelthorne Borough Council's guidance.
Two storey extension drawings for Sunbury-on-Thames — riverside period and suburban housing with the Lower Sunbury conservation area along the Thames — dimensioned against the 3m and 7m limits and drawn to Spelthorne Borough Council's guidance.
Two storey extension drawings for Shepperton — a historic Church Square village core and riverside studio-town character — dimensioned against the 3m and 7m limits and drawn to Spelthorne Borough Council's guidance.
Two storey extension drawings for Laleham — a small Thames-side conservation village of period and detached riverside houses — dimensioned against the 3m and 7m limits and drawn to Spelthorne Borough Council's guidance.
Two storey extension drawings for Stanwell — mixed postwar estate housing near Heathrow with its own conservation area — dimensioned against the 3m and 7m limits and drawn to Spelthorne Borough Council's guidance.
The first-floor limits are tighter than the ground-floor ones. This is how the common cases compare.
| Scheme | Permitted development? | Deciding limit | What Spelthorne Borough Council checks |
|---|---|---|---|
| Two-storey rear, 3m projection, 7m+ to boundary | Often yes | 3m projection / 7m boundary | Roof match, side-window glazing |
| Two-storey rear, under 7m to boundary | No — full application | Rear-boundary distance | Overlooking, daylight, garden loss |
| Two-storey side extension | No — full application | Side elevation | Gap to boundary, street rhythm |
| Two-storey wraparound | No — full application | Combined footprint | Bulk, massing, neighbour amenity |
| Any two-storey on designated land | No — full application | Designation | Character and appearance |
Limits from the GPDO 2015, Schedule 2, Part 1, Class A — two-storey rear extension conditions.
A fixed process built around how Spelthorne Borough Council validates and decides two-storey applications.
Send us your Spelthorne postcode and garden depth. We measure the 7-metre boundary rule against your plot, confirm designation status, and score your odds against live Spelthorne Borough Council decisions.
We measure the original rear wall, eaves and ridge heights, garden depth and every neighbouring window that faces the site — the inputs the daylight and overlooking case is built from.
Chartered designers develop the two-storey addition to your brief with the roof and eaves resolved, and we coordinate the load path so the structural scheme and the planning scheme are the same building.
We submit the application, manage validation and case-officer queries, and revise the drawings free until Spelthorne Borough Council issues its decision.
Often, but not always. A two-storey rear extension can be permitted development if it projects no more than 3 metres, sits at least 7 metres from the rear boundary, does not exceed the existing eaves and ridge, and has obscure-glazed non-opening side windows below 1.7 metres. In Spelthorne, the 7-metre rule is what most commonly forces a full application to Spelthorne Borough Council.
No part of a permitted-development two-storey rear extension may come within 7 metres of the boundary opposite the rear wall of the house. It exists to protect the neighbour behind you from being overlooked at first floor. On shorter Spelthorne gardens this is decisive, and we measure it on survey before any design work rather than discovering it at validation. Spelthorne Borough Council is the decision-maker.
Not under permitted development — two-storey side extensions always need a full application to Spelthorne Borough Council. They are assessed on the gap to the boundary, whether the street's rhythm of spaces between houses survives, and whether the extension is subordinate to the original. Setting the first floor back from the front building line and down from the ridge is what usually makes the difference.
Overlooking is the most common objection, and it is answerable on the drawings. We position habitable-room windows away from neighbouring gardens, obscure-glaze and fix shut anything on the flank below 1.7 metres, and show the sight lines in section. Where the geometry is tight, a rooflight or a high-level window gives the same daylight without the mutual overlooking that draws objections. This applies to your Spelthorne address specifically. Spelthorne Borough Council is the decision-maker.
Almost certainly. Excavating within 3 metres of a neighbouring structure and building on or up to the boundary both trigger the Party Wall etc. Act 1996, and a two-storey extension usually does both. It is entirely separate from Spelthorne Borough Council's planning decision, so we flag the notice period early and detail the junction on the drawings.
Yes. Adding a floor changes the load path from roof to foundation, so beams, padstones and foundation depths all need designing and calculating for building control. Planning and building regulations are separate consents, and the structural set is what building control assesses — we prepare both so the approved scheme is the buildable one. This applies to your Spelthorne address specifically. Spelthorne Borough Council is the decision-maker.
We quote each Spelthorne two-storey extension individually, because plot depth, roof form and structural complexity vary house to house, and send a fixed, no-obligation quote within one working day. It covers the drawing pack with free revisions until Spelthorne Borough Council approves. Call 020 7864 7245 to start.
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