Back-of-house extension drawings for Dorchester West homes — the glazed kitchen-diner across the rear, drawn to Dorset Council's depth and daylight limits, delivered in days and revised free until your decision, with a free approval-odds check first.
Dorset Council granted 95% of the householder planning decisions it made in its latest published year — 8 points above the 87% England-wide householder average. Dorchester West contains Dorchester Conservation Area 1, Dorchester Conservation Area 11, Dorchester Conservation Area 12 conservation areas (Dorchester Conservation Area 1 designated 1970), 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) 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. Dorchester West carries at least one Article 4 direction, and conservation areas including Dorchester Conservation Area 1, Dorchester Conservation Area 11 and Dorchester Conservation Area 12 remove those rights outright, so we confirm your exact address before a line is drawn. A validated householder application in Dorchester West is determined against an 8-week statutory target.
Dorchester Conservation Area 1 (conservation area designated in 1970), Dorchester Conservation Area 11 (conservation area designated in 1999), Dorchester Conservation Area 12 (conservation area designated in 2003), Dorchester Conservation Area 13 (conservation area designated in 2003), Dorchester Conservation Area 16 (conservation area designated in 2003), Dorchester Conservation Area 4 (conservation area designated in 1990), Dorchester Conservation Area 6 (conservation area designated in 1990), Dorchester Conservation Area 9 (conservation area designated in 1997) and Dorchester (civil parish within Dorchester West) — these are the Dorchester West pockets our drawings cover most. Heritage designations here include Dorchester Conservation Area 1, Dorchester Conservation Area 11, Dorchester Conservation Area 12, Dorchester Conservation Area 13, Dorchester Conservation Area 16, Dorchester Conservation Area 4, Dorchester Conservation Area 6 and Dorchester Conservation Area 9. Dorset Council weighs each proposal against Dorset Council's adopted local plan and its householder design guidance, where the 3,520 homes here are 24% pre-1900, 17% 1973-1982, 10% 1983-1992, 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 trussed roofs typical of 1970s building, over Victorian and earlier houses (24% of 3,520 homes), 1970s and early-1980s houses (17%) and 1980s estate houses (10%).
Before anything is drawn we check your address against the designations that apply in Dorchester West: Dorchester Conservation Area 1 (conservation area designated in 1970), Dorchester Conservation Area 11 (conservation area designated in 1999), Dorchester Conservation Area 12 (conservation area designated in 2003), Dorchester Conservation Area 13 (conservation area designated in 2003), Dorchester Conservation Area 16 (conservation area designated in 2003), Dorchester Conservation Area 4 (conservation area designated in 1990), Dorchester Conservation Area 6 (conservation area designated in 1990) and Dorchester Conservation Area 9 (conservation area designated in 1997). Inside those boundaries permitted development is curtailed and Dorset 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, Dorchester West takes in Dorchester. Dorset Council has 77 recorded Article 4 directions — check the address before assuming PD applies in Dorchester West.
On stock, Dorchester West is Victorian and earlier houses (24% of 3,520 homes), 1970s and early-1980s houses (17%) and 1980s estate houses (10%) — which is why steeply pitched slate roofs, valley gutters and party parapets typical of pre-1900 building and shallow trussed roofs typical of 1970s building govern what a loft or rear projection can realistically be. Dorset Council decided 1,261 householder applications in the latest published year and granted 95%, with 78% issued inside the eight-week target. That decision record, not a national figure, is what we design to.
The full build-period split for Dorchester West runs pre-1900 24% (860 homes), 1900-1918 3% (90 homes), 1919-1929 5% (190 homes), 1930-1939 7% (260 homes), 1945-1954 5% (180 homes), 1955-1964 4% (130 homes), 1965-1972 9% (330 homes), 1973-1982 17% (610 homes), 1983-1992 10% (360 homes), 1993-1999 2% (60 homes) and 2000-2008 6% (200 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.
Dorset Council also decides for Beacon, Beaminster, Blackmore Vale, Blandford, Chalk Valleys, Charminster St Mary's, Chickerell and Cranborne & Alderholt, so a decision in Dorchester West 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 1-3 The Lane, Kingston, Corfe Castle, 10 Cornwall Road, Swanage, 6 Burlington Road, Swanage and Avon Castle & Matchams Park Estate. 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 Dorchester West and Dorset Council. These are the numbers that decide what is realistic on your street, so we work from them rather than from national averages.
| Measure | Dorchester West |
|---|---|
| Dwellings recorded | 3,520 |
| Built pre-1900 | 860 (24%) |
| Built 1900-1918 | 90 (3%) |
| Built 1919-1929 | 190 (5%) |
| Built 1930-1939 | 260 (7%) |
| Built 1945-1954 | 180 (5%) |
| Built 1955-1964 | 130 (4%) |
| Built 1965-1972 | 330 (9%) |
| Built 1973-1982 | 610 (17%) |
| Built 1983-1992 | 360 (10%) |
| Built 1993-1999 | 60 (2%) |
| Built 2000-2008 | 200 (6%) |
| Built before 1919 | 27% |
| Built 1919–1939 | 13% |
| Built 1945–2008 | 53% |
| Conservation areas in Dorchester West | 8 (Dorchester Conservation Area 1, Dorchester Conservation Area 11…) |
| Conservation areas district-wide | 311 |
| Article 4 directions recorded | 77 |
| Householder applications decided | 1,261 |
| Householder applications granted | 95% |
| Decided within 8 weeks | 78% |
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 Dorset Council's own, from MHCLG live table PS2 for the year to 31 March 2026.
The rear extension is the workhorse of Dorchester West home improvement — it is how a dark back kitchen becomes an open family room facing the garden. Because the borough is built largely from Victorian and earlier houses (24% of 3,520 homes), 1970s and early-1980s houses (17%) and 1980s estate houses (10%), most back walls sit close to a neighbour on at least one side, and that proximity, not the design, is what Dorset Council scrutinises. The council reads the proposal against Dorset Council's adopted local plan and its householder design guidance, and the first line an officer draws is the 45-degree splay from the neighbour's nearest window.
So the drawings live or die on geometry. We set the depth against the exact permitted-development figure, hold the eaves and the flat-roof or lantern build-up under the 4-metre height ceiling, and show the projection tested against both the 45-degree plan angle and the 25-degree section angle to the neighbouring windows. Dorchester West contains Dorchester Conservation Area 1, Dorchester Conservation Area 11, Dorchester Conservation Area 12 conservation areas (Dorchester Conservation Area 1 designated 1970), so materials, fenestration and roof form are assessed against the appraisal, so the rear elevation is composed around it rather than corrected after an objection.
Where the property sits in a conservation area — Dorchester Conservation Area 1, Dorchester Conservation Area 11, Dorchester Conservation Area 12, Dorchester Conservation Area 13, Dorchester Conservation Area 16, Dorchester Conservation Area 4, Dorchester Conservation Area 6 and Dorchester Conservation Area 9 among Dorchester West's — the larger-home extension route is switched off and even a modest rear addition needs consent. Dorset Council has 77 recorded Article 4 directions — check the address before assuming PD applies in Dorchester West. We confirm the designation before the survey.
Many single-storey rear extensions in Dorchester West are permitted development and need no application. You will normally need to apply to Dorset Council, or use the larger-home prior-approval route, if any of these apply:
We draw the depth, the roof build-up and the daylight splays to each neighbour on the page — the tests Dorset Council's officers apply first — and submit a validation-complete pack, whether that is a lawful development certificate, a larger-home prior-approval notice or a full householder application.
Below is Dorset Council's real householder decision record, taken from official planning statistics and refreshed as new data lands. Dorset Council granted 95% of its householder applications in the year to 31 March 2026, and Dorchester Conservation Area 1 shapes what is approved here. Rear extensions turn most often on neighbour daylight and depth, so a drawing pack that proves those tests upfront is decided faster and refused less often than a DIY submission.
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 Dorchester Conservation Area 1, Dorchester Conservation Area 11 and Dorchester Conservation Area 12, the approved rear extension is typically a single-storey glazed box within the depth limit, roofed either flat with a lantern or in a shallow mono-pitch, and finished in brick or render to match the host wall. On the borough's victorian and earlier houses (24% of 3,520 homes), keeping the projection to the permitted-development figure often avoids an application entirely; where owners want the full 6 metres, the larger-home route succeeds when the neighbour-consultation period passes without a sustained objection.
The 3,520 homes here are 24% pre-1900, 17% 1973-1982, 10% 1983-1992, which is what sets the realistic roof and rear-projection options. We keep the extension inside the daylight splays, set any glazed roof below the first-floor cill, and retain the garden depth Dorset Council expects — so the back elevation answers the amenity case before a neighbour can lodge one. Two-storey rear extensions we draw with the 7-metre boundary gap and privacy screening resolved on the plan.
We draw rear extensions on every street in the borough. A few of the neighbourhoods where Dorchester West back-of-house projects come up most often:
Rear extension drawings for Dorchester Conservation Area 1's conservation area designated in 1970 — depth-checked, daylight-tested and drawn to Dorset Council's guidance.
Rear extension drawings for Dorchester Conservation Area 11's conservation area designated in 1999 — depth-checked, daylight-tested and drawn to Dorset Council's guidance.
Rear extension drawings for Dorchester Conservation Area 12's conservation area designated in 2003 — depth-checked, daylight-tested and drawn to Dorset Council's guidance.
Rear extension drawings for Dorchester Conservation Area 13's conservation area designated in 2003 — depth-checked, daylight-tested and drawn to Dorset Council's guidance.
Rear extension drawings for Dorchester Conservation Area 16's conservation area designated in 2003 — depth-checked, daylight-tested and drawn to Dorset Council's guidance.
Rear extension drawings for Dorchester Conservation Area 4's conservation area designated in 1990 — depth-checked, daylight-tested and drawn to Dorset Council's guidance.
How far you can extend at the back in Dorchester West depends on your house type and the route you take. This is how the options compare.
| Route | Depth allowed | Consent needed | What Dorset Council checks |
|---|---|---|---|
| Standard permitted development | 3m terrace/semi · 4m detached | Lawful development certificate (optional) | Depth, 4m height, materials |
| Larger-home prior approval | 6m terrace/semi · 8m detached | Prior-approval notice + neighbour consultation | Neighbour objections on amenity |
| Full householder application | Beyond the above, or two-storey | Full planning permission | Daylight (45°/25°), bulk, garden retained |
| Conservation area | Case by case | Full planning permission | Character, roof form, boundary treatment |
The larger-home route is switched off on designated land — conservation areas such as Dorchester Conservation Area 1 and Dorchester Conservation Area 11 and Article 4 streets need a full application.
A fixed process built around how Dorset Council validates and decides rear-extension applications — most drawings are submission-ready within seven days of survey.
Send us your Dorchester West postcode and house type. We confirm your conservation and Article 4 status, how much rear-extension depth you have under permitted development, and score your odds against live Dorset Council decisions.
We measure the original rear wall, floor and eaves levels, side and rear boundary distances and the neighbours' window positions — the numbers the depth limit and daylight splays depend on.
Chartered designers develop the single or two-storey rear extension to your brief, drawn inside the permitted-development limits or to Dorset Council's extension design guidance, with the daylight angles shown.
We submit the certificate, prior-approval notice or application, handle validation and case-officer queries, and revise the drawings free until Dorset Council issues its decision.
Often not. 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 Dorchester West. You will need to involve Dorset Council for anything deeper via the larger-home route, for two-storey rear extensions, and for any rear extension in a conservation area such as Dorchester Conservation Area 1 and Dorchester Conservation Area 11, where those permitted-development rights fall away.
The larger-home extension scheme lets a single-storey rear extension reach 6 metres on a terrace or semi, or 8 metres on a detached house — double the standard allowance. It is not automatic: you submit a prior-approval notification to Dorset Council, neighbours are consulted, and if one objects on amenity grounds the council rules on it. It also does not apply on designated land such as Dorchester West's conservation areas.
It is the daylight test Dorset Council applies to protect neighbours. Drawn on plan, a line at 45 degrees from the midpoint of the neighbour's nearest ground-floor window should not be crossed by your extension; a companion 25-degree line is checked in section. If the projection breaches it, the extension is likely to be shortened or refused, so we test and prove it on the drawings before submission. This applies to your Dorchester West address specifically.
A two-storey rear extension almost always needs a full householder application to Dorset Council, as it sits outside permitted development on most homes. The council checks that it stays at least 7 metres from the rear boundary, does not overbear the neighbours and avoids new overlooking. We resolve the boundary gap, privacy and daylight on the plans so the application is decided on its merits. This applies to your Dorchester West address specifically.
Frequently, yes. If the rear extension involves work to a shared wall, building up to the boundary, or excavating foundations near a neighbour's structure, the Party Wall etc. Act applies and you must serve notice — this is separate from Dorset Council's planning decision. We flag it early and can prepare the drawings a party-wall surveyor needs alongside the planning set. This applies to your Dorchester West address specifically.
We price each Dorchester West rear extension on its own footprint and send a fixed, no-obligation quote within one working day. It covers the full drawing pack with free revisions until Dorset Council approves, and we confirm at the outset whether your extension is permitted development, needs prior approval, or a full application. Call 020 7864 7245 to begin.
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