Two-storey extension drawings for Knebworth homes — bedroom above, living space below, drawn against the 3-metre projection and 7-metre boundary rules and to North Hertfordshire District Council's design guidance, delivered in days and revised free until your decision.
North Hertfordshire District Council granted 95% of the householder planning decisions it made in its latest published year — 8 points above the 87% England-wide householder average. Knebworth contains Deard's End Lane, Knebworth, Old Knebworth, Stockens Green Knebworth conservation areas (Deard's End Lane, Knebworth designated 2008), 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.
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 North Hertfordshire District Council needs a full application. In conservation areas such as Deard's End Lane, Knebworth, Old Knebworth and Stockens Green Knebworth those rights are removed, so we confirm your exact address before a line is drawn. A validated householder application in Knebworth is determined against an 8-week statutory target.
Deard's End Lane, Knebworth (conservation area designated in 2008), Old Knebworth (conservation area designated in 2008), Stockens Green Knebworth (conservation area designated in 2008) and Codicote (civil parish within Knebworth) — these are the Knebworth pockets our drawings cover most. Heritage designations here include Deard's End Lane, Knebworth, Old Knebworth and Stockens Green Knebworth. North Hertfordshire District Council weighs each proposal against North Hertfordshire District Council's adopted local plan and its householder design guidance, where the 2,510 homes here are 15% 1983-1992, 11% 1973-1982, 11% 1965-1972, which is what sets the realistic roof and rear-projection options. On roofs the borough is trussed-rafter roofs typical of 1980s building and shallow trussed roofs typical of 1970s building, over 1980s estate houses (15% of 2,510 homes), 1970s and early-1980s houses (11%) and late-1960s and early-1970s houses (11%).
Heritage designation is the single biggest variable in Knebworth, and it is address-specific: Deard's End Lane, Knebworth (conservation area designated in 2008), Old Knebworth (conservation area designated in 2008) and Stockens Green Knebworth (conservation area designated in 2008). Inside those boundaries permitted development is curtailed and North Hertfordshire 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, Knebworth takes in Codicote. No Article 4 direction is recorded for North Hertfordshire District Council, but Knebworth's 3 conservation areas still limit permitted development on those streets.
On stock, Knebworth is 1980s estate houses (15% of 2,510 homes), 1970s and early-1980s houses (11%) and late-1960s and early-1970s houses (11%) — which is why trussed-rafter roofs typical of 1980s building and shallow trussed roofs typical of 1970s building govern what a loft or rear projection can realistically be. North Hertfordshire District Council decided 665 householder applications in the latest published year and granted 95%, with 69% issued inside the eight-week target. We work from the council's own published record.
The full build-period split for Knebworth runs pre-1900 7% (170 homes), 1900-1918 8% (210 homes), 1919-1929 8% (200 homes), 1930-1939 10% (250 homes), 1945-1954 5% (130 homes), 1955-1964 8% (190 homes), 1965-1972 11% (270 homes), 1973-1982 11% (280 homes), 1983-1992 15% (370 homes), 1993-1999 2% (60 homes) and 2000-2008 3% (80 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.
North Hertfordshire District Council also decides for Arbury, Baldock West, Cadwell, Codicote & Kimpton, Ermine, Hitchin Priory, Hitchwood and Letchworth Norton, so a decision in Knebworth 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 Knebworth and North Hertfordshire 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 | Knebworth |
|---|---|
| Dwellings recorded | 2,510 |
| Built pre-1900 | 170 (7%) |
| Built 1900-1918 | 210 (8%) |
| Built 1919-1929 | 200 (8%) |
| Built 1930-1939 | 250 (10%) |
| Built 1945-1954 | 130 (5%) |
| Built 1955-1964 | 190 (8%) |
| Built 1965-1972 | 270 (11%) |
| Built 1973-1982 | 280 (11%) |
| Built 1983-1992 | 370 (15%) |
| Built 1993-1999 | 60 (2%) |
| Built 2000-2008 | 80 (3%) |
| Built before 1919 | 15% |
| Built 1919–1939 | 18% |
| Built 1945–2008 | 55% |
| Conservation areas in Knebworth | 3 (Deard's End Lane, Knebworth, Old Knebworth…) |
| Conservation areas district-wide | 44 |
| Article 4 directions recorded | 0 |
| Householder applications decided | 665 |
| Householder applications granted | 95% |
| Decided within 8 weeks | 69% |
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 North Hertfordshire District 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. Knebworth is largely 1980s estate houses (15% of 2,510 homes), 1970s and early-1980s houses (11%) and late-1960s and early-1970s houses (11%), and trussed-rafter roofs typical of 1980s building and shallow trussed roofs typical of 1970s 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.
Knebworth contains Deard's End Lane, Knebworth, Old Knebworth, Stockens Green Knebworth conservation areas (Deard's End Lane, Knebworth designated 2008), so materials, fenestration and roof form are assessed against the appraisal. No Article 4 direction is recorded for North Hertfordshire District Council, but Knebworth's 3 conservation areas still limit permitted development on those streets.
Some two-storey rear extensions are permitted development. You will need a full application to North Hertfordshire District 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 North Hertfordshire District Council checks first — then submit a validation-complete pack.
Below is North Hertfordshire District Council's real householder decision record, drawn from official planning statistics and refreshed as new data lands. North Hertfordshire District Council granted 95% of its householder applications in the year to 31 March 2026, and Deard's End Lane, Knebworth 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.
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 Deard's End Lane, Knebworth, Old Knebworth and Stockens Green Knebworth, 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 1980s estate houses (15% of 2,510 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 2,510 homes here are 15% 1983-1992, 11% 1973-1982, 11% 1965-1972, 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 Knebworth. A few of the areas where they come up most often:
Two storey extension drawings for Deard's End Lane, Knebworth — conservation area designated in 2008 — dimensioned against the 3m and 7m limits and drawn to North Hertfordshire District Council's guidance.
Two storey extension drawings for Old Knebworth — conservation area designated in 2008 — dimensioned against the 3m and 7m limits and drawn to North Hertfordshire District Council's guidance.
Two storey extension drawings for Stockens Green Knebworth — conservation area designated in 2008 — dimensioned against the 3m and 7m limits and drawn to North Hertfordshire District Council's guidance.
Two storey extension drawings for Codicote — civil parish within Knebworth — dimensioned against the 3m and 7m limits and drawn to North Hertfordshire District 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 North Hertfordshire District 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 North Hertfordshire District Council validates and decides two-storey applications.
Send us your Knebworth postcode and garden depth. We measure the 7-metre boundary rule against your plot, confirm designation status, and score your odds against live North Hertfordshire District 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 North Hertfordshire District 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 Knebworth, the 7-metre rule is what most commonly forces a full application to North Hertfordshire District 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 Knebworth gardens this is decisive, and we measure it on survey before any design work rather than discovering it at validation. North Hertfordshire District Council is the decision-maker.
Not under permitted development — two-storey side extensions always need a full application to North Hertfordshire District 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 Knebworth 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 Knebworth address specifically. North Hertfordshire District 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 North Hertfordshire District Council's planning decision, so we flag the notice period early and detail the junction on the drawings. This applies to your Knebworth 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 Knebworth address specifically. North Hertfordshire District Council is the decision-maker.
We quote each Knebworth 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 North Hertfordshire District Council approves. Call 020 7864 7245 to start.
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