The fast route to a deep single-storey rear extension in Chalk Valleys — up to 6 metres on an attached house or 8 on a detached one — via Dorset Council's prior approval scheme rather than a full planning application.
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. Chalk Valleys contains Alton Pancras Conservation Area, Buckland Newton Conservation Area, Cerne Abbas Conservation Area conservation areas (Alton Pancras Conservation Area designated 1990), 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.
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 Dorset Council needs a full application. Chalk Valleys carries at least one Article 4 direction, and conservation areas including Alton Pancras Conservation Area, Buckland Newton Conservation Area and Cerne Abbas Conservation Area remove those rights outright, so we confirm your exact address before a line is drawn. A validated householder application in Chalk Valleys is determined against an 8-week statutory target.
Alton Pancras (conservation area designated in 1990), Buckland Newton (conservation area designated in 1990), Cerne Abbas (conservation area designated in 1971), Dewlish (conservation area designated in 1990), Godmanstone (conservation area designated in 1990), Hilton (conservation area designated in 1971), Minterne Magna (conservation area designated in 1990), Piddlehinton (conservation area designated in 1990), Piddletrenthide (conservation area designated in 1990), Sydling St Nicholas (conservation area designated in 1973), Hilton (civil parish within Chalk Valleys), Alton Pancras (civil parish within Chalk Valleys), Buckland Newton (civil parish within Chalk Valleys), Cerne Abbas (civil parish within Chalk Valleys), Cheselbourne (civil parish within Chalk Valleys) and Dewlish (civil parish within Chalk Valleys) — these are the Chalk Valleys pockets our drawings cover most. Heritage designations here include Alton Pancras Conservation Area, Buckland Newton Conservation Area, Cerne Abbas Conservation Area, Dewlish Conservation Area, Godmanstone Conservation Area, Hilton Conservation Area, Minterne Magna Conservation Area, Piddlehinton Conservation Area, Piddletrenthide Conservation Area and Sydling St Nicholas Conservation Area. Dorset Council weighs each proposal against Dorset Council's development plan and the design policies it applies to householder applications, where the 1,020 homes here are 34% pre-1900, 13% 1983-1992, 10% 1973-1982, 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 trussed-rafter roofs typical of 1980s building, over Victorian and earlier houses (34% of 1,020 homes), 1980s estate houses (13%) and 1970s and early-1980s houses (10%).
Heritage designation is the single biggest variable in Chalk Valleys, and it is address-specific: Alton Pancras (conservation area designated in 1990), Buckland Newton (conservation area designated in 1990), Cerne Abbas (conservation area designated in 1971), Dewlish (conservation area designated in 1990), Godmanstone (conservation area designated in 1990), Hilton (conservation area designated in 1971), Minterne Magna (conservation area designated in 1990), Piddlehinton (conservation area designated in 1990), Piddletrenthide (conservation area designated in 1990) and Sydling St Nicholas (conservation area designated in 1973). 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, Chalk Valleys takes in Hilton, Alton Pancras, Buckland Newton, Cerne Abbas, Cheselbourne and Dewlish. Dorset Council has 77 recorded Article 4 directions — check the address before assuming PD applies in Chalk Valleys.
On stock, Chalk Valleys is Victorian and earlier houses (34% of 1,020 homes), 1980s estate houses (13%) and 1970s and early-1980s houses (10%) — which is why steeply pitched slate roofs, valley gutters and party parapets typical of pre-1900 building and trussed-rafter roofs typical of 1980s 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. We work from the council's own published record.
The full build-period split for Chalk Valleys runs pre-1900 34% (350 homes), 1900-1918 2% (20 homes), 1919-1929 1% (10 homes), 1930-1939 4% (40 homes), 1945-1954 5% (50 homes), 1955-1964 5% (50 homes), 1965-1972 6% (60 homes), 1973-1982 10% (100 homes), 1983-1992 13% (130 homes), 1993-1999 7% (70 homes) and 2000-2008 5% (50 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, Charminster St Mary's, Chickerell, Cranborne & Alderholt and Cranborne Chase, so a decision in Chalk Valleys 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 Chalk Valleys 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 | Chalk Valleys |
|---|---|
| Dwellings recorded | 1,020 |
| Built pre-1900 | 350 (34%) |
| Built 1900-1918 | 20 (2%) |
| Built 1919-1929 | 10 (1%) |
| Built 1930-1939 | 40 (4%) |
| Built 1945-1954 | 50 (5%) |
| Built 1955-1964 | 50 (5%) |
| Built 1965-1972 | 60 (6%) |
| Built 1973-1982 | 100 (10%) |
| Built 1983-1992 | 130 (13%) |
| Built 1993-1999 | 70 (7%) |
| Built 2000-2008 | 50 (5%) |
| Built before 1919 | 36% |
| Built 1919–1939 | 5% |
| Built 1945–2008 | 50% |
| Conservation areas in Chalk Valleys | 10 (Alton Pancras Conservation Area, Buckland Newton Conservation Area…) |
| 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 ordinary Class A limits stop a single-storey rear extension at 3 metres on an attached house and 4 on a detached one. The larger home extension scheme doubles both, on condition that the council is told first. That notification is not an application for permission — the council cannot refuse on design, materials or policy grounds. It can only consider the effect on the amenity of adjoining premises, and only if a neighbour actually objects during the 21-day consultation.
The other conditions still apply and are strict: single storey only, no higher than 4 metres, eaves no higher than the existing eaves, and no more than half the land around the original house covered. It is not available on designated land, so a house in a conservation area such as Alton Pancras Conservation Area and Buckland Newton Conservation Area cannot use it at all. Materials must be similar to the existing house, and the extension must not include a veranda, balcony or raised platform.
Chalk Valleys is largely Victorian and earlier houses (34% of 1,020 homes), 1980s estate houses (13%) and 1970s and early-1980s houses (10%). Chalk Valleys contains Alton Pancras Conservation Area, Buckland Newton Conservation Area, Cerne Abbas Conservation Area conservation areas (Alton Pancras Conservation Area designated 1990), so materials, fenestration and roof form are assessed against the appraisal, which matters here because an objecting neighbour puts amenity squarely in front of a case officer. Dorset Council has 77 recorded Article 4 directions — check the address before assuming PD applies in Chalk Valleys.
The scheme is available where all of these hold. Fail any one and it is a full application to Dorset Council instead:
We prepare the notification pack Dorset Council needs — plans, elevations, a site plan with the adjoining owners identified — and manage the 21-day neighbour consultation so the 42-day clock is not restarted by an incomplete submission.
Below is Dorset Council's real householder decision record, drawn 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 Alton Pancras Conservation Area shapes what is approved here. Prior approval turns on neighbour amenity alone, so the drawings that matter are the ones showing the relationship to the boundary.
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 Alton Pancras, Buckland Newton and Cerne Abbas, the notifications that clear without objection are the ones that treat the neighbour as the audience. We show the extension in section against the boundary, demonstrate the 45-degree daylight relationship to the nearest habitable window, and where the plot is tight we taper the depth away from the boundary rather than running the full 6 metres to the fence.
The 1,020 homes here are 34% pre-1900, 13% 1983-1992, 10% 1973-1982, which is what sets the realistic roof and rear-projection options. Where an objection does arrive, the council's assessment is narrow: loss of light, outlook and overbearing effect on the adjoining property, nothing else. A pack that has already answered those three points on the drawings usually survives an objection, whereas one that leaves them to the officer's imagination usually does not.
We prepare prior-approval notifications across Chalk Valleys. A few of the areas where deep rear extensions come up most often:
Prior approval drawings for Alton Pancras — conservation area designated in 1990 — dimensioned to the 6m and 8m limits and prepared for Dorset Council's neighbour consultation.
Prior approval drawings for Buckland Newton — conservation area designated in 1990 — dimensioned to the 6m and 8m limits and prepared for Dorset Council's neighbour consultation.
Prior approval drawings for Cerne Abbas — conservation area designated in 1971 — dimensioned to the 6m and 8m limits and prepared for Dorset Council's neighbour consultation.
Prior approval drawings for Dewlish — conservation area designated in 1990 — dimensioned to the 6m and 8m limits and prepared for Dorset Council's neighbour consultation.
Prior approval drawings for Godmanstone — conservation area designated in 1990 — dimensioned to the 6m and 8m limits and prepared for Dorset Council's neighbour consultation.
Prior approval drawings for Hilton — conservation area designated in 1971 — dimensioned to the 6m and 8m limits and prepared for Dorset Council's neighbour consultation.
Same extension, two routes, very different tests.
| Route | Depth allowed | What the council may consider | Timescale |
|---|---|---|---|
| Ordinary Class A permitted development | 3m attached / 4m detached | Nothing — no application needed | Immediate |
| Larger home extension prior approval | 6m attached / 8m detached | Amenity of adjoining premises, only if a neighbour objects | 21-day consultation, 42-day determination |
| Full householder application | No fixed limit | Design, materials, policy, amenity, everything | 8-week target |
| Any of these on designated land | 3m / 4m only | Prior approval scheme unavailable | Full application beyond the limits |
Limits and procedure from the GPDO 2015, Schedule 2, Part 1, Class A and paragraph A.4, made permanent by amendment in 2019.
A process built around the 21-day consultation, which is where these schemes are won or lost.
Send us your Chalk Valleys postcode and house type. We confirm whether the property is on designated land, whether the scheme is available, and what depth you can realistically take.
We measure the original rear wall, eaves height, boundary distances and the neighbouring windows that the amenity assessment will turn on.
We draw the extension to the 6m or 8m limit with the boundary relationship shown in section, and prepare the written description and adjoining-owner details Dorset Council needs to start the consultation.
We submit, track the 21-day consultation and the 42-day determination, respond to any objection on amenity grounds, and revise free until the decision.
Three metres on a terraced or semi-detached house and four on a detached one under ordinary permitted development. Under the larger home extension prior approval scheme those double to six and eight metres, provided you notify Dorset Council before starting and the conditions on height, materials and land coverage are met. The scheme is not available on designated land. This applies to your Chalk Valleys address specifically.
It is a notification, not an application for permission. You tell Dorset Council what you intend to build, it writes to the adjoining owners, and they have 21 days to object. If nobody objects, you may build. If someone does, the council assesses the effect on the amenity of adjoining premises and must decide within 42 days. Design and policy are not in scope. This applies to your Chalk Valleys address specifically.
The council then considers the impact on the amenity of the adjoining property — loss of light, loss of outlook, and overbearing effect — and nothing else. It cannot refuse because it dislikes the design or the materials. We prepare the drawings so those three questions are already answered in section and on the site plan, which is what usually carries an objected scheme through. This applies to your Chalk Valleys address specifically. Dorset Council is the decision-maker.
No. The larger home extension scheme is unavailable on designated land, which includes conservation areas such as Alton Pancras Conservation Area and Buckland Newton Conservation Area, national landscapes, national parks and world heritage sites. On those properties the ordinary 3-metre and 4-metre limits apply, and anything deeper needs a full householder application to Dorset Council. This applies to your Chalk Valleys address specifically.
Twenty-one days for the neighbour consultation, and a maximum of 42 days from a valid submission for the council to determine it. If the council does not respond within 42 days you may proceed as notified. That deadline is the scheme's real advantage over a full application, and it is why validation completeness matters so much. This applies to your Chalk Valleys address specifically. Dorset Council is the decision-maker.
Yes — always. Prior approval deals only with the planning position. A 6-metre rear extension still needs building control approval for foundations, structure, drainage, thermal performance and fire safety, and the beam over the opening into the existing house needs designing and calculating. We prepare both sets so the notified scheme is the buildable one. This applies to your Chalk Valleys address specifically. Dorset Council is the decision-maker.
We quote each Chalk Valleys scheme individually, because plot shape and the boundary relationship drive the work, and send a fixed, no-obligation quote within one working day. It covers the notification pack and free revisions until Dorset Council determines it. Call 020 7864 7245 to start.
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Same fixed quotes, same fast drawings — wherever your project is.