The fast route to a deep single-storey rear extension in Horsham — up to 6 metres on an attached house or 8 on a detached one — via Horsham District Council's prior approval scheme rather than a full planning application.
Horsham District Council granted 97% of the householder planning decisions it made in its latest published year — 10 points above the 87% England-wide householder average. Horsham contains Adversane Conservation Area, Billingshurst Conservation Area, Horsham (London Road) Conservation Area conservation areas (Adversane Conservation Area designated 1976), 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.
Under Class B, a rear dormer stays permitted development up to 40m³ of added roof volume on a terrace or 50m³ on a semi-detached or detached house, while Class A allows a single-storey rear extension of 3m beyond the original rear wall on a terrace and 4m on a detached house before a full application is needed. Horsham carries at least one Article 4 direction, and conservation areas including Adversane Conservation Area, Billingshurst Conservation Area and Horsham (London Road) Conservation Area remove those rights outright, so we confirm your exact address before a line is drawn. A validated householder application in Horsham is determined against an 8-week statutory target.
Adversane (conservation area designated in 1976), Billingshurst (conservation area designated in 2018), Horsham (London Road) (conservation area designated in 1984), Horsham (Park Terrace Gardens) (conservation area designated in 2023), Horsham (Richmond Road) (conservation area designated in 1989), Horsham (conservation area designated in 1974), Rusper (conservation area designated in 1976), Steyning (conservation area designated in 2018), Billingshurst (ward of Horsham), Colgate & Rusper (ward of Horsham), Denne (ward of Horsham), Holbrook West (ward of Horsham) and Steyning & Ashurst (ward of Horsham) — these are the Horsham pockets our drawings cover most. Heritage designations here include Adversane Conservation Area, Billingshurst Conservation Area, Horsham (London Road) Conservation Area, Horsham (Park Terrace Gardens) Conservation Area, Horsham (Richmond Road) Conservation Area, Horsham Conservation Area, Rusper Conservation Area and Steyning Conservation Area. Horsham District Council weighs each proposal against Horsham District Council's adopted local plan and its householder design guidance, where the 18,590 homes here are 7% 2000-2008, 6% 1983-1992, 6% 1973-1982, which is what sets the realistic roof and rear-projection options. On roofs the borough is trussed-rafter roofs typical of 2000s building and trussed-rafter roofs typical of 1980s building, over 2000s houses and apartments (7% of 18,590 homes), 1980s estate houses (6%) and 1970s and early-1980s houses (6%).
Horsham's designated heritage is specific, and it is the first thing we check against your address: Adversane (conservation area designated in 1976), Billingshurst (conservation area designated in 2018), Horsham (London Road) (conservation area designated in 1984), Horsham (Park Terrace Gardens) (conservation area designated in 2023), Horsham (Richmond Road) (conservation area designated in 1989), Horsham (conservation area designated in 1974), Rusper (conservation area designated in 1976) and Steyning (conservation area designated in 2018). Inside those boundaries permitted development is curtailed and Horsham District 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, Horsham takes in Billingshurst, Colgate & Rusper, Denne, Holbrook West and Steyning & Ashurst. Horsham District Council has 53 recorded Article 4 directions, removing permitted development for rear and side extensions and roof enlargements such as dormers — check the address before assuming PD applies in the district.
On stock, Horsham is 2000s houses and apartments (7% of 18,590 homes), 1980s estate houses (6%) and 1970s and early-1980s houses (6%) — which is why trussed-rafter roofs typical of 2000s building and trussed-rafter roofs typical of 1980s building govern what a loft or rear projection can realistically be. Horsham District Council decided 679 householder applications in the latest published year and granted 97%, with 72% issued inside the eight-week target. Those are the numbers our drawings are prepared against.
The full build-period split for Horsham runs pre-1900 3% (190 homes), 1900-1918 0% (30 homes), 1919-1929 0% (10 homes), 1930-1939 6% (350 homes), 1945-1954 3% (170 homes), 1955-1964 30% (1,850 homes), 1965-1972 33% (1,990 homes), 1973-1982 4% (260 homes), 1983-1992 5% (310 homes), 1993-1999 4% (220 homes) and 2000-2008 3% (170 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.
Horsham District Council also decides for Billingshurst, Colgate & Rusper, Denne, Holbrook West and Steyning & Ashurst, so a decision in Horsham 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 ART4002 - LAND AT WOLVENS FARM BILLINGSHURST ROAD ASHINGTON, ART4003 - LAND AT CODMORE HILL PULBOROUGH, ART4020/1 and ART4040. 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 Horsham and Horsham District Council. These are the numbers that decide what is realistic on your street, so we work from them rather than from national averages.
| Measure | Horsham |
|---|---|
| Dwellings recorded | 18,590 |
| Built pre-1900 | 190 (3%) |
| Built 1900-1918 | 30 (0%) |
| Built 1919-1929 | 10 (0%) |
| Built 1930-1939 | 350 (6%) |
| Built 1945-1954 | 170 (3%) |
| Built 1955-1964 | 1,850 (30%) |
| Built 1965-1972 | 1,990 (33%) |
| Built 1973-1982 | 260 (4%) |
| Built 1983-1992 | 310 (5%) |
| Built 1993-1999 | 220 (4%) |
| Built 2000-2008 | 170 (3%) |
| Built before 1919 | 11% |
| Built 1919–1939 | 6% |
| Built 1945–2008 | 58% |
| Conservation areas in Horsham | 8 (Adversane Conservation Area, Billingshurst Conservation Area…) |
| Conservation areas district-wide | 40 |
| Article 4 directions recorded | 53 |
| Householder applications decided | 679 |
| Householder applications granted | 97% |
| Decided within 8 weeks | 72% |
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 Horsham District 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 Adversane Conservation Area and Billingshurst 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.
Horsham is largely 2000s houses and apartments (7% of 18,590 homes), 1980s estate houses (6%) and 1970s and early-1980s houses (6%). Horsham contains Adversane Conservation Area, Billingshurst Conservation Area, Horsham (London Road) Conservation Area conservation areas (Adversane Conservation Area designated 1976), 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. Horsham District Council has 53 recorded Article 4 directions, removing permitted development for rear and side extensions and roof enlargements such as dormers — check the address before assuming PD applies in the district.
The scheme is available where all of these hold. Fail any one and it is a full application to Horsham District Council instead:
We prepare the notification pack Horsham District 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 Horsham District Council's real householder decision record, drawn from official planning statistics and refreshed as new data lands. Horsham District Council granted 97% of 679 householder decisions in the year to 31 March 2026, 72% of them inside eight weeks. 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 Adversane, Billingshurst and Horsham (London Road), 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 18,590 homes here are 7% 2000-2008, 6% 1983-1992, 6% 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 Horsham. A few of the areas where deep rear extensions come up most often:
Prior approval drawings for Adversane — conservation area designated in 1976 — dimensioned to the 6m and 8m limits and prepared for Horsham District Council's neighbour consultation.
Prior approval drawings for Billingshurst — conservation area designated in 2018 — dimensioned to the 6m and 8m limits and prepared for Horsham District Council's neighbour consultation.
Prior approval drawings for Horsham (London Road) — conservation area designated in 1984 — dimensioned to the 6m and 8m limits and prepared for Horsham District Council's neighbour consultation.
Prior approval drawings for Horsham (Park Terrace Gardens) — conservation area designated in 2023 — dimensioned to the 6m and 8m limits and prepared for Horsham District Council's neighbour consultation.
Prior approval drawings for Horsham (Richmond Road) — conservation area designated in 1989 — dimensioned to the 6m and 8m limits and prepared for Horsham District Council's neighbour consultation.
Prior approval drawings for Horsham — conservation area designated in 1974 — dimensioned to the 6m and 8m limits and prepared for Horsham District 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 Horsham 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 Horsham District 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 Horsham District Council before starting and the conditions on height, materials and land coverage are met. The scheme is not available on designated land.
It is a notification, not an application for permission. You tell Horsham District 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.
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 Horsham address specifically. Horsham District Council is the decision-maker.
No. The larger home extension scheme is unavailable on designated land, which includes conservation areas such as Adversane Conservation Area and Billingshurst 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 Horsham District Council.
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 Horsham address specifically. Horsham District 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 Horsham address specifically. Horsham District Council is the decision-maker.
We quote each Horsham 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 Horsham District Council determines it. 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.