Two-storey extension drawings for Aldenham West homes — bedroom above, living space below, drawn against the 3-metre projection and 7-metre boundary rules and to Hertsmere Borough Council's design guidance, delivered in days and revised free until your decision.
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. Aldenham West contains Aldenham, Letchmore Heath, Patchetts Green and Delrow 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 interwar (1918–1939) and postwar (1945–1970) 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 Hertsmere Borough Council needs a full application. In conservation areas such as Aldenham, Letchmore Heath and Patchetts Green and Delrow those rights are removed, so we confirm your exact address before a line is drawn. A validated householder application in Aldenham West is determined against an 8-week statutory target.
Aldenham (conservation area designated in 1973), Letchmore Heath (conservation area designated in 1969), Patchetts Green and Delrow (conservation area designated in 1998), Radlett North (conservation area designated in 1988), Round Bush (conservation area designated in 1978), Aldenham (civil parish within Aldenham West) and Hertsmere Meriden (civil parish within Aldenham West) — these are the Aldenham West pockets our drawings cover most. Heritage designations here include Aldenham, Letchmore Heath, Patchetts Green and Delrow, Radlett North and Round Bush. Hertsmere Borough Council weighs each proposal against Hertsmere Borough Council's adopted local plan and its householder design guidance, where the 2,100 homes here are 14% 1965-1972, 14% 1930-1939, 11% 1945-1954, which is what sets the realistic roof and rear-projection options. On roofs the borough is shallow-pitched roofs and integral garages typical of that period's building and hipped roofs with shallow pitches typical of 1930s building, over late-1960s and early-1970s houses (14% of 2,100 homes), 1930s semi-detached and detached houses (14%) and early postwar houses (11%).
Heritage designation is the single biggest variable in Aldenham West, and it is address-specific: Aldenham (conservation area designated in 1973), Letchmore Heath (conservation area designated in 1969), Patchetts Green and Delrow (conservation area designated in 1998), Radlett North (conservation area designated in 1988) and Round Bush (conservation area designated in 1978). 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, Aldenham West takes in Aldenham and Hertsmere Meriden. No Article 4 direction is recorded for Hertsmere Borough Council, but Aldenham West's 5 conservation areas still limit permitted development on those streets.
On stock, Aldenham West is late-1960s and early-1970s houses (14% of 2,100 homes), 1930s semi-detached and detached houses (14%) and early postwar houses (11%) — which is why shallow-pitched roofs and integral garages typical of that period's building and hipped roofs with shallow pitches typical of 1930s 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 work from the council's own published record.
The full build-period split for Aldenham West runs pre-1900 10% (220 homes), 1900-1918 5% (100 homes), 1919-1929 4% (90 homes), 1930-1939 14% (290 homes), 1945-1954 11% (240 homes), 1955-1964 8% (160 homes), 1965-1972 14% (300 homes), 1973-1982 2% (50 homes), 1983-1992 4% (80 homes), 1993-1999 7% (150 homes) and 2000-2008 10% (200 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, Bushey Heath, Bushey St James, Elstree and Shenley, so a decision in Aldenham West 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 Aldenham West 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 | Aldenham West |
|---|---|
| Dwellings recorded | 2,100 |
| Built pre-1900 | 220 (10%) |
| Built 1900-1918 | 100 (5%) |
| Built 1919-1929 | 90 (4%) |
| Built 1930-1939 | 290 (14%) |
| Built 1945-1954 | 240 (11%) |
| Built 1955-1964 | 160 (8%) |
| Built 1965-1972 | 300 (14%) |
| Built 1973-1982 | 50 (2%) |
| Built 1983-1992 | 80 (4%) |
| Built 1993-1999 | 150 (7%) |
| Built 2000-2008 | 200 (10%) |
| Built before 1919 | 15% |
| Built 1919–1939 | 18% |
| Built 1945–2008 | 56% |
| Conservation areas in Aldenham West | 5 (Aldenham, Letchmore Heath…) |
| 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.
Adding at first floor changes the question the case officer asks. A single-storey extension is judged mostly on daylight and garden loss; a two-storey extension is judged on overlooking, bulk against the neighbouring roofline, and whether it reads as part of the house or bolted onto it. Aldenham West is largely late-1960s and early-1970s houses (14% of 2,100 homes), 1930s semi-detached and detached houses (14%) and early postwar houses (11%), and shallow-pitched roofs and integral garages typical of that period's building and hipped roofs with shallow pitches typical of 1930s building set what a matching roof actually means here.
The permitted-development route exists but is narrow: 3 metres of rear projection, a 7-metre stand-off from the rear boundary, eaves and ridge no higher than the original, and side-facing upper windows obscure-glazed and non-opening below 1.7 metres above floor level. Most two-storey schemes fail one of those, usually the 7-metre boundary rule on a shorter garden, and go in as a full application instead. We establish which route applies before designing, because it changes the drawing set.
Aldenham West contains Aldenham, Letchmore Heath, Patchetts Green and Delrow conservation areas (Aldenham designated 1973), so materials, fenestration and roof form are assessed against the appraisal. No Article 4 direction is recorded for Hertsmere Borough Council, but Aldenham West's 5 conservation areas still limit permitted development on those streets.
Some two-storey rear extensions are permitted development. You will need a full application to Hertsmere Borough Council if any of these apply:
We set the projection and boundary distance on the site plan, prove the roof-pitch match on the elevations, and specify obscure glazing on the side windows — the three things Hertsmere Borough Council checks first — then submit a validation-complete pack.
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 its householder applications in the year to 31 March 2026, and Aldenham shapes what is approved here. Two-storey schemes attract more neighbour comment than any other householder work, so the overlooking and daylight case has to be made on the drawings.
Source: MHCLG planning application statistics (householder decisions, England, 1 April 2025 - 31 March 2026). Compare every borough on our London approval-rate league table.
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Across Aldenham, Letchmore Heath and Patchetts Green and Delrow, the schemes that succeed set the first floor back from the ground floor, keep the ridge below the original, and treat the flank wall as blank or obscure-glazed. On late-1960s and early-1970s houses (14% of 2,100 homes), matching the eaves line matters more than matching the brick: an extension that carries the existing eaves through reads as original even in a different material.
The 2,100 homes here are 14% 1965-1972, 14% 1930-1939, 11% 1945-1954, which is what sets the realistic roof and rear-projection options. We draw the 45-degree daylight test from the neighbour's nearest habitable window, show the window positions in section, and set out the steel and foundation implications early — a two-storey extension changes the load path, so the structural design and the planning design have to be developed together rather than in sequence.
We draw two-storey extensions across Aldenham West. A few of the areas where they come up most often:
Two storey extension drawings for Aldenham — conservation area designated in 1973 — dimensioned against the 3m and 7m limits and drawn to Hertsmere Borough Council's guidance.
Two storey extension drawings for Letchmore Heath — conservation area designated in 1969 — dimensioned against the 3m and 7m limits and drawn to Hertsmere Borough Council's guidance.
Two storey extension drawings for Patchetts Green and Delrow — conservation area designated in 1998 — dimensioned against the 3m and 7m limits and drawn to Hertsmere Borough Council's guidance.
Two storey extension drawings for Radlett North — conservation area designated in 1988 — dimensioned against the 3m and 7m limits and drawn to Hertsmere Borough Council's guidance.
Two storey extension drawings for Round Bush — conservation area designated in 1978 — dimensioned against the 3m and 7m limits and drawn to Hertsmere Borough Council's guidance.
Two storey extension drawings for Aldenham — civil parish within Aldenham West — dimensioned against the 3m and 7m limits and drawn to Hertsmere Borough Council's guidance.
The first-floor limits are tighter than the ground-floor ones. This is how the common cases compare.
| Scheme | Permitted development? | Deciding limit | What Hertsmere Borough Council checks |
|---|---|---|---|
| Two-storey rear, 3m projection, 7m+ to boundary | Often yes | 3m projection / 7m boundary | Roof match, side-window glazing |
| Two-storey rear, under 7m to boundary | No — full application | Rear-boundary distance | Overlooking, daylight, garden loss |
| Two-storey side extension | No — full application | Side elevation | Gap to boundary, street rhythm |
| Two-storey wraparound | No — full application | Combined footprint | Bulk, massing, neighbour amenity |
| Any two-storey on designated land | No — full application | Designation | Character and appearance |
Limits from the GPDO 2015, Schedule 2, Part 1, Class A — two-storey rear extension conditions.
A fixed process built around how Hertsmere Borough Council validates and decides two-storey applications.
Send us your Aldenham West postcode and garden depth. We measure the 7-metre boundary rule against your plot, confirm designation status, and score your odds against live Hertsmere Borough Council decisions.
We measure the original rear wall, eaves and ridge heights, garden depth and every neighbouring window that faces the site — the inputs the daylight and overlooking case is built from.
Chartered designers develop the two-storey addition to your brief with the roof and eaves resolved, and we coordinate the load path so the structural scheme and the planning scheme are the same building.
We submit the application, manage validation and case-officer queries, and revise the drawings free until Hertsmere Borough Council issues its decision.
Often, but not always. A two-storey rear extension can be permitted development if it projects no more than 3 metres, sits at least 7 metres from the rear boundary, does not exceed the existing eaves and ridge, and has obscure-glazed non-opening side windows below 1.7 metres. In Aldenham West, the 7-metre rule is what most commonly forces a full application to Hertsmere Borough Council.
No part of a permitted-development two-storey rear extension may come within 7 metres of the boundary opposite the rear wall of the house. It exists to protect the neighbour behind you from being overlooked at first floor. On shorter Aldenham West gardens this is decisive, and we measure it on survey before any design work rather than discovering it at validation. Hertsmere Borough Council is the decision-maker.
Not under permitted development — two-storey side extensions always need a full application to Hertsmere Borough Council. They are assessed on the gap to the boundary, whether the street's rhythm of spaces between houses survives, and whether the extension is subordinate to the original. Setting the first floor back from the front building line and down from the ridge is what usually makes the difference. This applies to your Aldenham West address specifically.
Overlooking is the most common objection, and it is answerable on the drawings. We position habitable-room windows away from neighbouring gardens, obscure-glaze and fix shut anything on the flank below 1.7 metres, and show the sight lines in section. Where the geometry is tight, a rooflight or a high-level window gives the same daylight without the mutual overlooking that draws objections. This applies to your Aldenham West address specifically. Hertsmere Borough Council is the decision-maker.
Almost certainly. Excavating within 3 metres of a neighbouring structure and building on or up to the boundary both trigger the Party Wall etc. Act 1996, and a two-storey extension usually does both. It is entirely separate from Hertsmere Borough Council's planning decision, so we flag the notice period early and detail the junction on the drawings. This applies to your Aldenham West address specifically.
Yes. Adding a floor changes the load path from roof to foundation, so beams, padstones and foundation depths all need designing and calculating for building control. Planning and building regulations are separate consents, and the structural set is what building control assesses — we prepare both so the approved scheme is the buildable one. This applies to your Aldenham West address specifically. Hertsmere Borough Council is the decision-maker.
We quote each Aldenham West two-storey extension individually, because plot depth, roof form and structural complexity vary house to house, and send a fixed, no-obligation quote within one working day. It covers the drawing pack with free revisions until Hertsmere Borough Council approves. Call 020 7864 7245 to start.
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