Dormer, hip-to-gable and mansard loft conversion drawings for By Brook homes — prepared to Wiltshire Council's design guidance, delivered in days and revised free until your decision lands, with a free approval-odds score first.
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's roofs set the brief. 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%), and its lofts sit under 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 — the geometry that decides whether a rear dormer, a hip-to-gable or a mansard gives you the headroom you want. Wiltshire Council assesses loft proposals against Wiltshire Council's development plan and the design policies it applies to householder applications, and its case officers read each roof against the pair next door and the wider street before they read the plans.
That makes drawing quality decisive. We measure ridge and eaves heights, roof pitch and the existing stair, calculate the added volume against the permitted-development limits exactly, and show the workings on the drawings so Wiltshire Council can verify them. 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 resolve it on the page rather than leave it for the case officer to raise.
By Brook also carries protected 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. We check your address against those designations before a line is drawn.
Many By Brook loft conversions proceed without planning permission — a rear dormer within the permitted-development volume limits (40 cubic metres on a terrace, 50 on a semi or detached house) is usually lawful. You will normally need a full application to Wiltshire Council if any of these apply:
We draw the roof line, the ridge height and the neighbour's daylight on the page — the relationships Wiltshire Council's officers check first — and submit a validation-complete pack, whether that is a lawful development certificate or a full householder application.
Below is Wiltshire Council's real householder decision record, pulled from official planning statistics and updated 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. Professionally prepared loft drawings anticipate those pressure points before submission, which is why complete, policy-literate packs are decided faster and refused less often than DIY applications.
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 recurring loft is the rear dormer — a box across the back roof slope that turns a cramped attic into a full-height double bedroom and en-suite. On steeply pitched slate roofs, valley gutters and party parapets typical of pre-1900 building, that is usually the most efficient use of the roof; where the stock is shallow-pitched roofs and integral garages typical of that period's building, a hip-to-gable followed by a rear dormer unlocks far more space, though it needs a full application.
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 draw the dormer inside the volume allowance, keep the flat-roof build-up below the ridge, and set the face back from the eaves as the rules require — so the pack answers Wiltshire Council's questions before they are asked. Where permitted-development rights are exhausted or removed, we prepare a householder application composed to the borough's roof-alteration guidance instead.
We draw loft conversions on every street in the borough. A few of the neighbourhoods where By Brook roofs come up most often:
Loft conversion drawings for BIDDESTONE's conservation area designated in 1973 — measured, volume-checked and drawn to Wiltshire Council's guidance.
Loft conversion drawings for CASTLE COMBE's conservation area designated in 1973 — measured, volume-checked and drawn to Wiltshire Council's guidance.
Loft conversion drawings for GRITTLETON's conservation area designated in 1973 — measured, volume-checked and drawn to Wiltshire Council's guidance.
Loft conversion drawings for HULLAVINGTON AIRBASE's designated conservation area — measured, volume-checked and drawn to Wiltshire Council's guidance.
Loft conversion drawings for LEIGH DELAMERE's designated conservation area — measured, volume-checked and drawn to Wiltshire Council's guidance.
Loft conversion drawings for LITTLETON DREW's designated conservation area — measured, volume-checked and drawn to Wiltshire Council's guidance.
The right loft in By Brook depends on your roof. This is how the main types compare on planning route and the space they add.
| Loft type | Permitted development? | Space & headroom | What Wiltshire Council checks |
|---|---|---|---|
| Rear dormer | Usually yes, within volume limits | Full-height double room at the back | Volume, set-back from eaves, ridge height |
| Hip-to-gable | No — full application | Extends the whole side of the roof | Roof bulk and the symmetry of the pair |
| Mansard | No — full application | Maximum floor area across the roof | Street character, especially in conservation areas |
| Rooflights only | Usually yes (Class C) | Light and headroom, no extra footprint | Whether rooflights sit within the existing slope |
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 loft applications — most drawings are submission-ready within seven days of survey.
Tell us your By Brook postcode and roof type. We confirm your conservation and Article 4 status, how much permitted-development volume you have left, and score your odds against live Wiltshire Council decisions.
We measure ridge and eaves heights, roof pitch, joist levels and the existing stair — the numbers the volume calculation and head heights depend on.
Chartered designers develop the dormer, hip-to-gable or mansard to your brief, drawn inside the Class B limits or to Wiltshire Council's roof-alteration guidance.
We submit the certificate or application, manage validation and case-officer queries, and revise the drawings free until Wiltshire Council issues its decision.
Often not. A rear dormer within 40 cubic metres on a terrace, or 50 on a semi-detached or detached house, set back from the eaves and no higher than the ridge, is usually permitted development. In By Brook the main exceptions are hip-to-gable conversions, dormers visible from the highway, and homes in conservation areas such as BIDDESTONE and CASTLE COMBE or on streets with an Article 4 direction. Wiltshire Council is the decision-maker.
Generally no. In conservation areas including BIDDESTONE and CASTLE COMBE, Class B permitted-development rights for lofts are removed, so a rear dormer that would be lawful elsewhere needs a full application to Wiltshire Council. 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. We check your exact address before drawing.
On steeply pitched slate roofs, valley gutters and party parapets typical of pre-1900 building, common across By Brook, a rear dormer is usually the most efficient conversion and often permitted development. Where the roof is shallow-pitched roofs and integral garages typical of that period's building, a hip-to-gable followed by a rear dormer gains far more usable space but needs planning permission. Our survey confirms which your roof supports before we draw. Wiltshire Council is the decision-maker.
A householder planning application in By Brook runs to a statutory eight-week target, and a lawful development certificate to eight weeks as well, though validation can add time if the pack is incomplete. We submit validation-complete drawings and manage case-officer queries to keep the decision on track. Wiltshire Council is the decision-maker.
If your dormer is permitted development, a lawful development certificate from Wiltshire Council is council-stamped proof of that — worth having, because every buyer's solicitor will ask for it when you sell. We prepare and submit the certificate application with the same drawing pack. This applies to your By Brook address specifically.
Every roof is different, so we quote each By Brook project individually — a fixed, no-obligation price back within one working day. The quote covers the full drawing pack with free revisions until Wiltshire Council approves, and we tell you upfront whether your loft qualifies as permitted development. Call 020 7864 7245 to start.
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.