Two-storey extension drawings for Colnbrook & Poyle homes — bedroom above, living space below, drawn against the 3-metre projection and 7-metre boundary rules and to Slough Borough Council's design guidance, delivered in days and revised free until your decision.
Slough Borough Council granted 82% of the householder planning decisions it made in its latest published year — 5 points below the 87% England-wide householder average. Colnbrook & Poyle contains the Colnbrook conservation area, so materials, fenestration and roof form are assessed against the appraisal, which is where a policy-literate drawing pack earns its keep. Its mixed housing stock sets the design brief street by street.
The permitted-development ceilings are fixed: 40m³ of new roof volume for a terraced loft and 50m³ for a semi or detached house under Class B, plus a 3m single-storey rear extension on a terrace or 4m on a detached house under Class A. In conservation areas such as Colnbrook those rights are removed, so we confirm your exact address before a line is drawn. A validated householder application in Colnbrook & Poyle is determined against an 8-week statutory target.
Colnbrook (designated conservation area) and Colnbrook with Poyle (civil parish within Colnbrook & Poyle) — these are the Colnbrook & Poyle pockets our drawings cover most. Heritage designations here include Colnbrook. Slough Borough Council weighs each proposal against Slough Borough Council's adopted local plan and its householder design guidance, where the 3,130 homes here are 19% 1973-1982, 19% 2000-2008, 15% 1983-1992, which is what sets the realistic roof and rear-projection options. On roofs the borough is shallow trussed roofs typical of 1970s building and trussed-rafter roofs typical of 2000s building, over 1970s and early-1980s houses (19% of 3,130 homes), 2000s houses and apartments (19%) and 1980s estate houses (15%).
Before anything is drawn we check your address against the designations that apply in Colnbrook & Poyle: Colnbrook (designated conservation area). Inside those boundaries permitted development is curtailed and Slough Borough Council assesses materials, window detail and roof form against the area's own appraisal, so a scheme that would be waved through two streets away can need a full application here.
Beyond the designated areas, Colnbrook & Poyle takes in Colnbrook with Poyle. No Article 4 direction is recorded for Slough Borough Council, but Colnbrook & Poyle's 1 conservation area still limit permitted development on those streets.
On stock, Colnbrook & Poyle is 1970s and early-1980s houses (19% of 3,130 homes), 2000s houses and apartments (19%) and 1980s estate houses (15%) — which is why shallow trussed roofs typical of 1970s building and trussed-rafter roofs typical of 2000s building govern what a loft or rear projection can realistically be. Slough Borough Council decided 417 householder applications in the latest published year and granted 82%, with 42% issued inside the eight-week target. That decision record, not a national figure, is what we design to.
The full build-period split for Colnbrook & Poyle runs pre-1900 5% (160 homes), 1900-1918 1% (30 homes), 1919-1929 2% (50 homes), 1930-1939 7% (220 homes), 1945-1954 0% (10 homes), 1955-1964 9% (290 homes), 1965-1972 13% (410 homes), 1973-1982 19% (610 homes), 1983-1992 15% (480 homes), 1993-1999 2% (60 homes) and 2000-2008 19% (580 homes). That distribution is why pre-1900 detailing dominates the drawings here, and it is measured from council-tax records rather than assumed from the street name.
Slough Borough Council also decides for Langley St Mary's, so a decision in Colnbrook & Poyle sits inside a wider pattern of decisions we track across the same authority — useful when an officer cites a precedent from the next area over.
Published figures for Colnbrook & Poyle and Slough Borough Council. These are the numbers that decide what is realistic on your street, so we work from them rather than from national averages.
| Measure | Colnbrook & Poyle |
|---|---|
| Dwellings recorded | 3,130 |
| Built pre-1900 | 160 (5%) |
| Built 1900-1918 | 30 (1%) |
| Built 1919-1929 | 50 (2%) |
| Built 1930-1939 | 220 (7%) |
| Built 1945-1954 | 10 (0%) |
| Built 1955-1964 | 290 (9%) |
| Built 1965-1972 | 410 (13%) |
| Built 1973-1982 | 610 (19%) |
| Built 1983-1992 | 480 (15%) |
| Built 1993-1999 | 60 (2%) |
| Built 2000-2008 | 580 (19%) |
| Built before 1919 | 6% |
| Built 1919–1939 | 9% |
| Built 1945–2008 | 78% |
| Conservation areas in Colnbrook & Poyle | 1 (Colnbrook) |
| Conservation areas district-wide | 5 |
| Article 4 directions recorded | 0 |
| Householder applications decided | 417 |
| Householder applications granted | 82% |
| Decided within 8 weeks | 42% |
Dwelling stock from VOA council-tax data at 31 March 2025; conservation-area and Article 4 counts from planning.data.gov.uk (MHCLG); decision figures are Slough Borough Council's own, from MHCLG live table PS2 for the year to 31 March 2026.
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. Colnbrook & Poyle is largely 1970s and early-1980s houses (19% of 3,130 homes), 2000s houses and apartments (19%) and 1980s estate houses (15%), and shallow trussed roofs typical of 1970s building and trussed-rafter roofs typical of 2000s building 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.
Colnbrook & Poyle contains the Colnbrook conservation area, so materials, fenestration and roof form are assessed against the appraisal. No Article 4 direction is recorded for Slough Borough Council, but Colnbrook & Poyle's 1 conservation area still limit permitted development on those streets.
Some two-storey rear extensions are permitted development. You will need a full application to Slough 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 Slough Borough Council checks first — then submit a validation-complete pack.
Below is Slough Borough Council's real householder decision record, drawn from official planning statistics and refreshed as new data lands. Slough Borough Council granted 82% of its householder applications in the year to 31 March 2026, and Colnbrook shapes what is approved here. 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.
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Across Colnbrook and Colnbrook with Poyle, 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 1970s and early-1980s houses (19% of 3,130 homes), 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.
The 3,130 homes here are 19% 1973-1982, 19% 2000-2008, 15% 1983-1992, which is what sets the realistic roof and rear-projection options. 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 Colnbrook & Poyle. A few of the areas where they come up most often:
Two storey extension drawings for Colnbrook — designated conservation area — dimensioned against the 3m and 7m limits and drawn to Slough Borough Council's guidance.
Two storey extension drawings for Colnbrook with Poyle — civil parish within Colnbrook & Poyle — dimensioned against the 3m and 7m limits and drawn to Slough 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 Slough 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 Slough Borough Council validates and decides two-storey applications.
Send us your Colnbrook & Poyle postcode and garden depth. We measure the 7-metre boundary rule against your plot, confirm designation status, and score your odds against live Slough 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 Slough 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 Colnbrook & Poyle, the 7-metre rule is what most commonly forces a full application to Slough 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 Colnbrook & Poyle gardens this is decisive, and we measure it on survey before any design work rather than discovering it at validation. Slough Borough Council is the decision-maker.
Not under permitted development — two-storey side extensions always need a full application to Slough 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. This applies to your Colnbrook & Poyle address specifically.
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 Colnbrook & Poyle address specifically. Slough 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 Slough Borough Council's planning decision, so we flag the notice period early and detail the junction on the drawings. This applies to your Colnbrook & Poyle address specifically.
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 Colnbrook & Poyle address specifically. Slough Borough Council is the decision-maker.
We quote each Colnbrook & Poyle 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 Slough Borough Council approves. Call 020 7864 7245 to start.
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