Single-storey, double-storey, rear and side extension drawings for St Albans homes — measured to St Albans City & District Council's design guidance, delivered in days and revised free until your decision, with a free approval-odds check before you commit.
St Albans City & District Council granted 88% of the householder planning decisions it made in its latest published year — 1 point above the 87% England-wide householder average. Over 80 per cent of the district is Metropolitan Green Belt, the dominant constraint and the reason the emerging plan must justify green-belt release, which is where a policy-literate drawing pack earns its keep. Its dominant Georgian (1714–1837), Victorian (1837–1901), Edwardian (1901–1910), interwar (1918–1939) and 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. St Albans carries at least one Article 4 direction, and conservation areas including St Albans city centre, Fishpool Street and St Michael's Village remove those rights outright, so we confirm your exact address before a line is drawn. A validated householder application in St Albans is determined against an 8-week statutory target.
St Albans city centre (the medieval and Georgian historic core around the cathedral and Fishpool Street), Harpenden (affluent commuter town of Edwardian and interwar semis and detached houses), Marshalswick (interwar and postwar St Albans suburb of detached houses and semis), Redbourn (historic village with a large common, period cottages and modern infill), Wheathampstead (historic village between St Albans and Harpenden) and London Colney (large village with mixed twentieth-century estate housing) — these are the St Albans pockets our drawings cover most. Heritage designations here include St Albans city centre, Fishpool Street, St Michael's Village, Verulamium, Harpenden and Redbourn. St Albans City & District Council weighs each proposal against the saved 1994 St Albans District Local Plan Review, with a new Local Plan to 2041 at examination, where the historic city core carries dense conservation coverage layered over the scheduled Roman remains at Verulamium. Converted flats concentrate in the city centre and along the commuter-rail corridors, and carry no householder permitted-development rights.. On roofs the borough is pitched plain-clay-tile roofs on the historic core and hipped roofs on the interwar suburban semis, over medieval, Georgian and Victorian stock in the historic city core, Victorian and Edwardian commuter terraces, interwar and postwar suburban semis and detached houses in Marshalswick, Harpenden and the larger villages and period cottages in the green-belt villages.
St Albans homes come in a handful of recurring shapes, and each one points to a different extension. The borough is built largely from medieval, Georgian and Victorian stock in the historic city core, Victorian and Edwardian commuter terraces, interwar and postwar suburban semis and detached houses in Marshalswick, Harpenden and the larger villages and period cottages in the green-belt villages, 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. St Albans City & District Council judges every one of them against the saved 1994 St Albans District Local Plan Review, with a new Local Plan to 2041 at examination, 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. Over 80 per cent of the district is Metropolitan Green Belt, the dominant constraint and the reason the emerging plan must justify green-belt release, so we design around it from the first sketch rather than discover it at validation.
St Albans also protects whole streets — St Albans city centre, Fishpool Street, St Michael's Village, Verulamium, Harpenden and Redbourn among them. The Verulam and Fishpool Street Article 4 direction, covering the historic core around Fishpool Street and St Michael's, removes permitted-development rights so even minor external changes to these medieval and Georgian frontages need consent. 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 St Albans 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 St Albans City & 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 St Albans City & 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 St Albans City & District Council's real householder decision record, drawn from official planning statistics and refreshed as new data lands. St Albans grants a fair share of householder applications, with near-total green-belt coverage and the sensitivity of the historic city core the constraints behind most refusals. 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 St Albans city centre, Harpenden and Marshalswick, 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 medieval, georgian and victorian stock in the historic city core, a side-return infill frequently pairs with it to square off the plan; on wider period cottages in the green-belt villages, a two-storey side or rear extension can add a bedroom above without swallowing the garden.
The historic city core carries dense conservation coverage layered over the scheduled Roman remains at Verulamium. 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 St Albans City & 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 St Albans projects come up most often:
Extension drawings for St Albans city centre's the medieval and Georgian historic core around the cathedral and Fishpool Street — footprint-checked, daylight-tested and drawn to St Albans City & District Council's guidance.
Extension drawings for Harpenden's affluent commuter town of Edwardian and interwar semis and detached houses — footprint-checked, daylight-tested and drawn to St Albans City & District Council's guidance.
Extension drawings for Marshalswick's interwar and postwar St Albans suburb of detached houses and semis — footprint-checked, daylight-tested and drawn to St Albans City & District Council's guidance.
Extension drawings for Redbourn's historic village with a large common, period cottages and modern infill — footprint-checked, daylight-tested and drawn to St Albans City & District Council's guidance.
Extension drawings for Wheathampstead's historic village between St Albans and Harpenden — footprint-checked, daylight-tested and drawn to St Albans City & District Council's guidance.
Extension drawings for London Colney's large village with mixed twentieth-century estate housing — footprint-checked, daylight-tested and drawn to St Albans City & District Council's guidance.
The right extension in St Albans 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 St Albans City & 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 St Albans city centre and Fishpool Street and Article 4 directions can remove permitted-development rights.
A fixed process built around how St Albans City & District Council validates and decides householder extension applications — most drawings are submission-ready within seven days of survey.
Tell us your St Albans 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 St Albans City & 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 St Albans City & 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 St Albans City & 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 St Albans you will need to apply to St Albans City & 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 St Albans city centre and Fishpool Street.
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 St Albans City & District Council and a neighbour-consultation period, and it does not apply on designated land such as St Albans'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 St Albans City & 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 St Albans 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. St Albans City & 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 St Albans City & District Council's building control or an approved inspector can sign the work off.
Every house and brief is different, so we price each St Albans extension individually and send a fixed, no-obligation quote back within one working day. It covers the full drawing pack with free revisions until St Albans City & District Council approves, and we tell you upfront whether your extension qualifies as permitted development. Call 020 7864 7245 to get started.
Answer five quick questions and get a free planning score for your exact address — instantly. Then, if you want the full picture, unlock the detailed analysis: your council's live approval rates, local precedents, constraints on your street and a step-by-step route to permission.
Same fixed quotes, same fast drawings — wherever your project is.