Single-storey, double-storey, rear and side extension drawings for Horsham homes — measured to Horsham District Council's design guidance, delivered in days and revised free until your decision, with a free approval-odds check before you commit.
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.
Horsham homes come in a handful of recurring shapes, and each one points to a different extension. The borough is built largely from 2000s houses and apartments (7% of 18,590 homes), 1980s estate houses (6%) and 1970s and early-1980s houses (6%), 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. Horsham District Council judges every one of them against Horsham District Council's adopted local plan and its householder design guidance, 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. 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, so we design around it from the first sketch rather than discover it at validation.
Horsham also protects whole streets — 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 among them. 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 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 Horsham 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 Horsham District Council if any of these apply:
We draw the footprint, the ridge and eaves heights and the neighbours' daylight on the page — the relationships Horsham District 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 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. 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 Adversane, Billingshurst and Horsham (London Road), 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 2000s houses and apartments (7% of 18,590 homes), a side-return infill frequently pairs with it to square off the plan; on wider 1970s and early-1980s houses (6%), a two-storey side or rear extension can add a bedroom above without swallowing the garden.
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. 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 Horsham District 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 Horsham projects come up most often:
Extension drawings for Adversane's conservation area designated in 1976 — footprint-checked, daylight-tested and drawn to Horsham District Council's guidance.
Extension drawings for Billingshurst's conservation area designated in 2018 — footprint-checked, daylight-tested and drawn to Horsham District Council's guidance.
Extension drawings for Horsham (London Road)'s conservation area designated in 1984 — footprint-checked, daylight-tested and drawn to Horsham District Council's guidance.
Extension drawings for Horsham (Park Terrace Gardens)'s conservation area designated in 2023 — footprint-checked, daylight-tested and drawn to Horsham District Council's guidance.
Extension drawings for Horsham (Richmond Road)'s conservation area designated in 1989 — footprint-checked, daylight-tested and drawn to Horsham District Council's guidance.
Extension drawings for Horsham's conservation area designated in 1974 — footprint-checked, daylight-tested and drawn to Horsham District Council's guidance.
The right extension in Horsham 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 Horsham District 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 Adversane Conservation Area and Billingshurst Conservation Area and Article 4 directions can remove permitted-development rights.
A fixed process built around how Horsham District Council validates and decides householder extension applications — most drawings are submission-ready within seven days of survey.
Tell us your Horsham 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 Horsham District 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 Horsham District 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 Horsham District 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 Horsham you will need to apply to Horsham District 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 Adversane Conservation Area and Billingshurst Conservation Area.
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 Horsham District Council and a neighbour-consultation period, and it does not apply on designated land such as Horsham'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 Horsham District 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.
A householder planning application in Horsham 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. Horsham District 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 Horsham District Council's building control or an approved inspector can sign the work off.
Every house and brief is different, so we price each Horsham extension individually and send a fixed, no-obligation quote back within one working day. It covers the full drawing pack with free revisions until Horsham District 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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