Side-return infill drawings for Hertsmere terraces — the glazed extension that fills the redundant side alley and opens up the kitchen, drawn to Hertsmere Borough Council's guidance, delivered in days and revised free until your decision, with a free approval-odds check first.
Hertsmere Borough Council granted 94% of the householder planning decisions it made in its latest published year — 7 points above the 87% England-wide householder average. Hertsmere contains Aldenham, Bushey Heath High Road, Bushey Heath The Lake conservation areas (Aldenham designated 1973), so materials, fenestration and roof form are assessed against the appraisal, which is where a policy-literate drawing pack earns its keep. Its dominant postwar (1945–1970) housing stock sets the design brief on most streets.
Before permission is required, Class B allows 40m³ of added loft volume on a terrace and 50m³ on a semi or detached house, and Class A allows a 3m single-storey rear extension on a terrace or 4m on a detached house. In conservation areas such as Aldenham, Bushey Heath High Road and Bushey Heath The Lake those rights are removed, so we confirm your exact address before a line is drawn. A validated householder application in Hertsmere is determined against an 8-week statutory target.
Aldenham (conservation area designated in 1973), Bushey Heath High Road (conservation area designated in 1990), Bushey Heath The Lake (conservation area designated in 1998), Bushey High Street (conservation area designated in 1973), Bushey Melbourne Road (conservation area designated in 1973), Elstree Village (conservation area designated in 1976), Letchmore Heath (conservation area designated in 1969), Patchetts Green and Delrow (conservation area designated in 1998), Aldenham East (ward of Hertsmere), Aldenham West (ward of Hertsmere), Bushey Heath (ward of Hertsmere), Bushey St James (ward of Hertsmere), Elstree (ward of Hertsmere) and Shenley (ward of Hertsmere) — these are the Hertsmere pockets our drawings cover most. Heritage designations here include Aldenham, Bushey Heath High Road, Bushey Heath The Lake, Bushey High Street, Bushey Melbourne Road, Elstree Village, Letchmore Heath and Patchetts Green and Delrow. Hertsmere Borough Council weighs each proposal against the adopted Hertsmere local plan and Hertsmere Borough Council's design guidance for householder work, where the 13,370 homes here are 15% 1955-1964, 8% 1965-1972, 7% 1993-1999, which is what sets the realistic roof and rear-projection options. On roofs the borough is shallow gabled roofs typical of that period's building and shallow-pitched roofs and integral garages typical of that period's building, over late-1950s and early-1960s houses (15% of 13,370 homes), late-1960s and early-1970s houses (8%) and 1990s estate houses (7%).
What is permitted in Hertsmere turns on designation first, so that is where we start: Aldenham (conservation area designated in 1973), Bushey Heath High Road (conservation area designated in 1990), Bushey Heath The Lake (conservation area designated in 1998), Bushey High Street (conservation area designated in 1973), Bushey Melbourne Road (conservation area designated in 1973), Elstree Village (conservation area designated in 1976), Letchmore Heath (conservation area designated in 1969) and Patchetts Green and Delrow (conservation area designated in 1998). Inside those boundaries permitted development is curtailed and Hertsmere Borough 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, Hertsmere takes in Aldenham East, Aldenham West, Bushey Heath, Bushey St James, Elstree and Shenley. No Article 4 direction is recorded for Hertsmere Borough Council, but the district's 8 conservation areas still limit permitted development on those streets.
On stock, Hertsmere is late-1950s and early-1960s houses (15% of 13,370 homes), late-1960s and early-1970s houses (8%) and 1990s estate houses (7%) — which is why shallow gabled roofs typical of that period's building and shallow-pitched roofs and integral garages typical of that period's building govern what a loft or rear projection can realistically be. Hertsmere Borough Council decided 466 householder applications in the latest published year and granted 94%, with 49% issued inside the eight-week target. We draw to that record rather than to a national average.
The full build-period split for Hertsmere 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.
Hertsmere Borough Council also decides for Aldenham East, Aldenham West, Bushey Heath, Bushey St James, Elstree and Shenley, so a decision in Hertsmere 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.
Published figures for Hertsmere and Hertsmere Borough Council. These are the numbers that decide what is realistic on your street, so we work from them rather than from national averages.
| Measure | Hertsmere |
|---|---|
| Dwellings recorded | 13,370 |
| 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 | 13% |
| Built 1919–1939 | 14% |
| Built 1945–2008 | 60% |
| Conservation areas in Hertsmere | 8 (Aldenham, Bushey Heath High Road…) |
| Conservation areas district-wide | 16 |
| Article 4 directions recorded | 0 |
| Householder applications decided | 466 |
| Householder applications granted | 94% |
| Decided within 8 weeks | 49% |
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 Hertsmere Borough Council's own, from MHCLG live table PS2 for the year to 31 March 2026.
The side return is the classic terrace fix, and Hertsmere has the stock for it — the borough is built largely from late-1950s and early-1960s houses (15% of 13,370 homes), late-1960s and early-1970s houses (8%) and 1990s estate houses (7%), 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. Hertsmere Borough Council judges the infill against the adopted Hertsmere local plan and Hertsmere Borough Council's design guidance for householder work, 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. Hertsmere contains Aldenham, Bushey Heath High Road, Bushey Heath The Lake conservation areas (Aldenham designated 1973), 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 Hertsmere's terraces sit in conservation areas — Aldenham, Bushey Heath High Road, Bushey Heath The Lake, Bushey High Street, Bushey Melbourne Road, Elstree Village, Letchmore Heath and Patchetts Green and Delrow among them — where a side extension is no longer permitted development. No Article 4 direction is recorded for Hertsmere Borough Council, but the district's 8 conservation areas still limit permitted development on those streets. We confirm the designation before a line is drawn.
Some single-storey side returns in Hertsmere 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 Hertsmere Borough 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 Hertsmere Borough 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 Hertsmere Borough Council's real householder decision record, drawn from official planning statistics and refreshed as new data lands. Hertsmere Borough Council granted 94% of 466 householder decisions in the year to 31 March 2026, 49% 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 Aldenham, Bushey Heath High Road and Bushey Heath The Lake, 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 late-1950s and early-1960s houses (15% of 13,370 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 13,370 homes here are 15% 1955-1964, 8% 1965-1972, 7% 1993-1999, 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 Hertsmere Borough 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 Hertsmere side returns come up most often:
Side return extension drawings for Aldenham's conservation area designated in 1973 — width-checked, party-wall detailed and drawn to Hertsmere Borough Council's guidance.
Side return extension drawings for Bushey Heath High Road's conservation area designated in 1990 — width-checked, party-wall detailed and drawn to Hertsmere Borough Council's guidance.
Side return extension drawings for Bushey Heath The Lake's conservation area designated in 1998 — width-checked, party-wall detailed and drawn to Hertsmere Borough Council's guidance.
Side return extension drawings for Bushey High Street's conservation area designated in 1973 — width-checked, party-wall detailed and drawn to Hertsmere Borough Council's guidance.
Side return extension drawings for Bushey Melbourne Road's conservation area designated in 1973 — width-checked, party-wall detailed and drawn to Hertsmere Borough Council's guidance.
Side return extension drawings for Elstree Village's conservation area designated in 1976 — width-checked, party-wall detailed and drawn to Hertsmere Borough Council's guidance.
Whether a side return in Hertsmere 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 Hertsmere Borough 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 Aldenham and Bushey Heath High Road, side extensions are not permitted development and always need a full application.
A fixed process built around how Hertsmere Borough Council validates and decides side-return applications — most drawings are submission-ready within seven days of survey.
Send us your Hertsmere 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 Hertsmere Borough 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 Hertsmere Borough 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 Hertsmere Borough 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 Hertsmere you will need a full application to Hertsmere Borough Council for anything wider or taller, for a two-storey side return, and for any side extension in a conservation area such as Aldenham and Bushey Heath High Road, 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. Hertsmere's period terraces are ideally suited to it, which is why the side return is one of the borough's most common extensions. Hertsmere Borough 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 Hertsmere Borough 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 Hertsmere Borough 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 Hertsmere 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. Hertsmere Borough Council is the decision-maker.
We price each Hertsmere 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 Hertsmere Borough 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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