Single-storey, double-storey, rear and side extension drawings for By Brook homes — measured to Wiltshire Council's design guidance, delivered in days and revised free until your decision, with a free approval-odds check before you commit.
Wiltshire Council granted 96% of the householder planning decisions it made in its latest published year — 9 points above the 87% England-wide householder average. By Brook contains BIDDESTONE, CASTLE COMBE, GRITTLETON conservation areas (BIDDESTONE designated 1973), so materials, fenestration and roof form are assessed against the appraisal, which is where a policy-literate drawing pack earns its keep. Its dominant Victorian (1837–1901) and postwar (1945–1970) housing stock sets the design brief on most streets.
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. By Brook carries at least one Article 4 direction, and conservation areas including BIDDESTONE, CASTLE COMBE and GRITTLETON remove those rights outright, so we confirm your exact address before a line is drawn. A validated householder application in By Brook is determined against an 8-week statutory target.
BIDDESTONE (conservation area designated in 1973), CASTLE COMBE (conservation area designated in 1973), GRITTLETON (conservation area designated in 1973), HULLAVINGTON AIRBASE (designated conservation area), LEIGH DELAMERE (designated conservation area), LITTLETON DREW (designated conservation area), LONG DEAN - FORD - SLAUGHTERFORD (designated conservation area), NORTH WRAXALL (designated conservation area), SEVINGTON (designated conservation area), UPPER WRAXALL (designated conservation area), WEST KINGTON (conservation area designated in 1975), YATTON KEYNELL (designated conservation area), Hullavington (civil parish within By Brook), Nettleton (civil parish within By Brook), North Wraxall (civil parish within By Brook), Biddestone and Slaughterford (civil parish within By Brook), Castle Combe (civil parish within By Brook) and Grittleton (civil parish within By Brook) — these are the By Brook pockets our drawings cover most. Heritage designations here include BIDDESTONE, CASTLE COMBE, GRITTLETON, HULLAVINGTON AIRBASE, LEIGH DELAMERE, LITTLETON DREW, LONG DEAN - FORD - SLAUGHTERFORD, NORTH WRAXALL, SEVINGTON, UPPER WRAXALL, WEST KINGTON and YATTON KEYNELL. Wiltshire Council weighs each proposal against Wiltshire Council's development plan and the design policies it applies to householder applications, where the 2,320 homes here are 35% pre-1900, 10% 1965-1972, 7% 1945-1954, which is what sets the realistic roof and rear-projection options. On roofs the borough is steeply pitched slate roofs, valley gutters and party parapets typical of pre-1900 building and shallow-pitched roofs and integral garages typical of that period's building, over Victorian and earlier houses (35% of 2,320 homes), late-1960s and early-1970s houses (10%) and early postwar houses (7%).
Before anything is drawn we check your address against the designations that apply in By Brook: BIDDESTONE (conservation area designated in 1973), CASTLE COMBE (conservation area designated in 1973), GRITTLETON (conservation area designated in 1973), HULLAVINGTON AIRBASE (designated conservation area), LEIGH DELAMERE (designated conservation area), LITTLETON DREW (designated conservation area), LONG DEAN - FORD - SLAUGHTERFORD (designated conservation area), NORTH WRAXALL (designated conservation area), SEVINGTON (designated conservation area), UPPER WRAXALL (designated conservation area), WEST KINGTON (conservation area designated in 1975) and YATTON KEYNELL (designated conservation area). Inside those boundaries permitted development is curtailed and Wiltshire 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, By Brook takes in Hullavington, Nettleton, North Wraxall, Biddestone and Slaughterford, Castle Combe and Grittleton. Wiltshire Council has 48 recorded Article 4 directions, removing permitted development for rear and side extensions and other roof alterations, including rooflights — check the address before assuming PD applies in By Brook.
On stock, By Brook is Victorian and earlier houses (35% of 2,320 homes), late-1960s and early-1970s houses (10%) and early postwar houses (7%) — which is why steeply pitched slate roofs, valley gutters and party parapets typical of pre-1900 building and shallow-pitched roofs and integral garages typical of that period's building govern what a loft or rear projection can realistically be. Wiltshire Council decided 1,779 householder applications in the latest published year and granted 96%, with 53% issued inside the eight-week target. That decision record, not a national figure, is what we design to.
The full build-period split for By Brook runs pre-1900 35% (820 homes), 1900-1918 2% (50 homes), 1919-1929 0% (10 homes), 1930-1939 4% (100 homes), 1945-1954 7% (170 homes), 1955-1964 6% (150 homes), 1965-1972 10% (240 homes), 1973-1982 6% (140 homes), 1983-1992 7% (160 homes), 1993-1999 6% (130 homes) and 2000-2008 7% (160 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.
Wiltshire Council also decides for Aldbourne & Ramsbury, Amesbury West, Avon Valley, Box & Colerne, Corsham Ladbrook, Corsham Pickwick, Corsham Without and Cricklade & Latton, so a decision in By Brook 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.
The Article 4 directions recorded for this council include Ashley, Avebury, Baydon 1 and Baydon 2. Each removes a specific permitted-development right inside its own boundary, which is why the check is done on the address rather than on the town.
Published figures for By Brook and Wiltshire Council. These are the numbers that decide what is realistic on your street, so we work from them rather than from national averages.
| Measure | By Brook |
|---|---|
| Dwellings recorded | 2,320 |
| Built pre-1900 | 820 (35%) |
| Built 1900-1918 | 50 (2%) |
| Built 1919-1929 | 10 (0%) |
| Built 1930-1939 | 100 (4%) |
| Built 1945-1954 | 170 (7%) |
| Built 1955-1964 | 150 (6%) |
| Built 1965-1972 | 240 (10%) |
| Built 1973-1982 | 140 (6%) |
| Built 1983-1992 | 160 (7%) |
| Built 1993-1999 | 130 (6%) |
| Built 2000-2008 | 160 (7%) |
| Built before 1919 | 38% |
| Built 1919–1939 | 5% |
| Built 1945–2008 | 50% |
| Conservation areas in By Brook | 12 (BIDDESTONE, CASTLE COMBE…) |
| Conservation areas district-wide | 245 |
| Article 4 directions recorded | 48 |
| Householder applications decided | 1,779 |
| Householder applications granted | 96% |
| Decided within 8 weeks | 53% |
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 Wiltshire Council's own, from MHCLG live table PS2 for the year to 31 March 2026.
By Brook homes come in a handful of recurring shapes, and each one points to a different extension. The borough is built largely from Victorian and earlier houses (35% of 2,320 homes), late-1960s and early-1970s houses (10%) and early postwar houses (7%), 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. Wiltshire Council judges every one of them against Wiltshire Council's development plan and the design policies it applies to householder applications, 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. By Brook contains BIDDESTONE, CASTLE COMBE, GRITTLETON conservation areas (BIDDESTONE designated 1973), so materials, fenestration and roof form are assessed against the appraisal, so we design around it from the first sketch rather than discover it at validation.
By Brook also protects whole streets — BIDDESTONE, CASTLE COMBE, GRITTLETON, HULLAVINGTON AIRBASE, LEIGH DELAMERE, LITTLETON DREW, LONG DEAN - FORD - SLAUGHTERFORD, NORTH WRAXALL, SEVINGTON, UPPER WRAXALL, WEST KINGTON and YATTON KEYNELL among them. Wiltshire Council has 48 recorded Article 4 directions, removing permitted development for rear and side extensions and other roof alterations, including rooflights — check the address before assuming PD applies in By Brook. 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 By Brook 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 Wiltshire Council if any of these apply:
We draw the footprint, the ridge and eaves heights and the neighbours' daylight on the page — the relationships Wiltshire 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 Wiltshire Council's real householder decision record, drawn from official planning statistics and refreshed as new data lands. Wiltshire Council granted 96% of its householder applications in the year to 31 March 2026, and BIDDESTONE shapes what is approved here. 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 BIDDESTONE, CASTLE COMBE and GRITTLETON, 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 victorian and earlier houses (35% of 2,320 homes), a side-return infill frequently pairs with it to square off the plan; on wider early postwar houses (7%), a two-storey side or rear extension can add a bedroom above without swallowing the garden.
The 2,320 homes here are 35% pre-1900, 10% 1965-1972, 7% 1945-1954, which is what sets the realistic roof and rear-projection options. 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 Wiltshire 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 By Brook projects come up most often:
Extension drawings for BIDDESTONE's conservation area designated in 1973 — footprint-checked, daylight-tested and drawn to Wiltshire Council's guidance.
Extension drawings for CASTLE COMBE's conservation area designated in 1973 — footprint-checked, daylight-tested and drawn to Wiltshire Council's guidance.
Extension drawings for GRITTLETON's conservation area designated in 1973 — footprint-checked, daylight-tested and drawn to Wiltshire Council's guidance.
Extension drawings for HULLAVINGTON AIRBASE's designated conservation area — footprint-checked, daylight-tested and drawn to Wiltshire Council's guidance.
Extension drawings for LEIGH DELAMERE's designated conservation area — footprint-checked, daylight-tested and drawn to Wiltshire Council's guidance.
Extension drawings for LITTLETON DREW's designated conservation area — footprint-checked, daylight-tested and drawn to Wiltshire Council's guidance.
The right extension in By Brook 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 Wiltshire 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 BIDDESTONE and CASTLE COMBE and Article 4 directions can remove permitted-development rights.
A fixed process built around how Wiltshire Council validates and decides householder extension applications — most drawings are submission-ready within seven days of survey.
Tell us your By Brook 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 Wiltshire 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 Wiltshire 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 Wiltshire 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 By Brook you will need to apply to Wiltshire 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 BIDDESTONE and CASTLE COMBE.
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 Wiltshire Council and a neighbour-consultation period, and it does not apply on designated land such as By Brook'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 Wiltshire 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. This applies to your By Brook address specifically.
A householder planning application in By Brook 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. Wiltshire 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 Wiltshire Council's building control or an approved inspector can sign the work off. This applies to your By Brook address specifically.
Every house and brief is different, so we price each By Brook extension individually and send a fixed, no-obligation quote back within one working day. It covers the full drawing pack with free revisions until Wiltshire Council approves, and we tell you upfront whether your extension qualifies as permitted development. Call 020 7864 7245 to get started.
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