Side-return infill drawings for Horsham terraces — the glazed extension that fills the redundant side alley and opens up the kitchen, drawn to Horsham District Council's guidance, delivered in days and revised free until your decision, with a free approval-odds check first.
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 side return is the classic terrace fix, and Horsham has the stock for it — 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%), and the Victorian and Edwardian versions almost all have an L-shaped back addition with a wasted alley beside it. Fill that alley and the dark galley kitchen becomes a bright, square room the full width of the house. Horsham District Council judges the infill against Horsham District Council's adopted local plan and its householder design guidance, and because it runs along the party boundary, the neighbour relationship is read before the design.
That boundary is where the drawings earn their keep. We set the infill wall on or up to the line, keep the roof — usually a glazed lantern or a shallow pitch tying into the existing back-addition slope — below the neighbour's first-floor windows, and detail the rainwater and party-wall junction so the build is watertight and the Party Wall Act is satisfied. 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 resolve it on the section rather than leave it to the case officer.
Many of Horsham's terraces sit in conservation areas — 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 — where a side extension is no longer permitted development. 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. We confirm the designation before a line is drawn.
Some single-storey side returns in Horsham are permitted development, but the width and boundary make an application more likely than for a straight rear extension. You will normally need to apply to Horsham District Council if any of these apply:
We draw the infill wall on the boundary, the glazed roof below the neighbour's windows and the party-wall junction on the page — the details Horsham District Council's officers and your neighbour both check — and submit a validation-complete pack, whether that is a lawful development certificate 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. Side returns hinge on width, roof glazing and the party boundary, so a pack that resolves those details 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 Adversane, Billingshurst and Horsham (London Road), the approved side return is a single-storey infill roofed with a glazed lantern or roof light to pull daylight deep into the plan, its flank wall built on the boundary and finished to match the host brick. On the borough's 2000s houses and apartments (7% of 18,590 homes), this is frequently the single biggest gain in usable ground-floor space, and where it stays within the width and height limits it can proceed under permitted development or a lawful development certificate.
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 keep the glazed roof below the neighbour's cill line, set the gutter and the party-wall flashing so water and maintenance are designed in, and — where owners want the full open-plan room — pair the infill with a rear extension as a single wraparound application. That way Horsham District Council sees one coherent scheme rather than two overlapping ones.
We draw side-return infills on every terraced street in the borough. A few of the neighbourhoods where Horsham side returns come up most often:
Side return extension drawings for Adversane's conservation area designated in 1976 — width-checked, party-wall detailed and drawn to Horsham District Council's guidance.
Side return extension drawings for Billingshurst's conservation area designated in 2018 — width-checked, party-wall detailed and drawn to Horsham District Council's guidance.
Side return extension drawings for Horsham (London Road)'s conservation area designated in 1984 — width-checked, party-wall detailed and drawn to Horsham District Council's guidance.
Side return extension drawings for Horsham (Park Terrace Gardens)'s conservation area designated in 2023 — width-checked, party-wall detailed and drawn to Horsham District Council's guidance.
Side return extension drawings for Horsham (Richmond Road)'s conservation area designated in 1989 — width-checked, party-wall detailed and drawn to Horsham District Council's guidance.
Side return extension drawings for Horsham's conservation area designated in 1974 — width-checked, party-wall detailed and drawn to Horsham District Council's guidance.
Whether a side return in Horsham needs permission comes down to width, storeys and whether the street is designated. This is how the cases compare.
| Side return type | Permitted development? | What it gains | What Horsham District Council checks |
|---|---|---|---|
| Single-storey infill, within limits | Often yes, if under half the house width | Full-width kitchen-diner | Width, 4m height, roof glazing |
| Single-storey, over half width | No — full application | Wider room, more light | Boundary treatment, neighbour amenity |
| Two-storey side return | No — full application | Room above as well as below | Bulk, overlooking, terrace rhythm |
| Wraparound (side + rear) | No — full application | L-shaped open-plan ground floor | Combined footprint, garden retained |
In conservation areas such as Adversane Conservation Area and Billingshurst Conservation Area, side extensions are not permitted development and always need a full application.
A fixed process built around how Horsham District Council validates and decides side-return applications — most drawings are submission-ready within seven days of survey.
Send us your Horsham postcode and terrace type. We confirm your conservation and Article 4 status, whether the infill stays within the side-extension width limit, and score your odds against live Horsham District Council decisions.
We measure the side alley, the back-addition wall, floor and eaves levels and the neighbour's window heights — the numbers the width limit, roof pitch and party-wall detailing depend on.
Chartered designers develop the infill and its glazed roof to your brief, drawn inside the permitted-development limits or to Horsham District Council's extension guidance, with the boundary and party-wall junction detailed.
We submit the certificate or application, manage validation and case-officer queries, and revise the drawings free until Horsham District Council issues its decision.
Sometimes not. A single-storey side-return infill can be permitted development if it is no wider than half the original house, no higher than 4 metres, and the property is not on designated land. In Horsham you will need a full application to Horsham District Council for anything wider or taller, for a two-storey side return, and for any side extension in a conservation area such as Adversane Conservation Area and Billingshurst Conservation Area, where those rights are removed.
It is an infill that fills the narrow open alley running alongside the rear back-addition of a Victorian or Edwardian terrace — the strip of ground that is usually too small to use. Building over it squares off the ground floor, so a cramped galley kitchen becomes a full-width room. Horsham's period terraces are ideally suited to it, which is why the side return is one of the borough's most common extensions. Horsham District Council is the decision-maker.
Almost always. A side return is built on or up to the boundary with your neighbour, so the Party Wall etc. Act applies and you must serve notice before work starts — this is entirely separate from Horsham District Council's planning decision. We detail the party-wall junction on the drawings and flag the notice early so a surveyor can be appointed without delaying the build.
Yes, and it is common — the combined L-shape is a wraparound extension. Once the side infill joins a rear projection beyond the permitted-development depth, the whole thing needs a full householder application to Horsham District Council rather than qualifying as permitted development. We draw it as one coherent scheme so the council assesses a single footprint, which reads more clearly than two overlapping proposals.
A householder planning application in Horsham runs to a statutory eight-week target, and a lawful development certificate to eight weeks as well, though an incomplete pack can stall at validation. Because a side return involves the boundary and roof glazing, a complete, well-detailed submission matters — we prepare it validation-complete and manage officer queries to keep the decision on track. Horsham District Council is the decision-maker.
We price each Horsham side return individually, because alley width and roof form vary house to house, and send a fixed, no-obligation quote within one working day. It covers the full drawing pack with free revisions until Horsham District Council approves, and we confirm at the outset whether your infill is permitted development or needs an application. Call 020 7864 7245 to start.
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