Back-of-house extension drawings for St Albans homes — the glazed kitchen-diner across the rear, drawn to St Albans City & District Council's depth and daylight limits, delivered in days and revised free until your decision, with a free approval-odds check first.
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.
The rear extension is the workhorse of St Albans home improvement — it is how a dark back kitchen becomes an open family room facing the garden. Because 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, most back walls sit close to a neighbour on at least one side, and that proximity, not the design, is what St Albans City & District Council scrutinises. The council reads the proposal against the saved 1994 St Albans District Local Plan Review, with a new Local Plan to 2041 at examination, and the first line an officer draws is the 45-degree splay from the neighbour's nearest window.
So the drawings live or die on geometry. We set the depth against the exact permitted-development figure, hold the eaves and the flat-roof or lantern build-up under the 4-metre height ceiling, and show the projection tested against both the 45-degree plan angle and the 25-degree section angle to the neighbouring windows. 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 the rear elevation is composed around it rather than corrected after an objection.
Where the property sits in a conservation area — St Albans city centre, Fishpool Street, St Michael's Village, Verulamium, Harpenden and Redbourn among St Albans's — the larger-home extension route is switched off and even a modest rear addition needs consent. 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. We confirm the designation before the survey.
Many single-storey rear extensions in St Albans are permitted development and need no application. You will normally need to apply to St Albans City & District Council, or use the larger-home prior-approval route, if any of these apply:
We draw the depth, the roof build-up and the daylight splays to each neighbour on the page — the tests St Albans City & District Council's officers apply first — and submit a validation-complete pack, whether that is a lawful development certificate, a larger-home prior-approval notice or a full householder application.
Below is St Albans City & District Council's real householder decision record, taken 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. Rear extensions turn most often on neighbour daylight and depth, so a drawing pack that proves those tests 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 St Albans city centre, Harpenden and Marshalswick, the approved rear extension is typically a single-storey glazed box within the depth limit, roofed either flat with a lantern or in a shallow mono-pitch, and finished in brick or render to match the host wall. On the borough's medieval, georgian and victorian stock in the historic city core, keeping the projection to the permitted-development figure often avoids an application entirely; where owners want the full 6 metres, the larger-home route succeeds when the neighbour-consultation period passes without a sustained objection.
The historic city core carries dense conservation coverage layered over the scheduled Roman remains at Verulamium. We keep the extension inside the daylight splays, set any glazed roof below the first-floor cill, and retain the garden depth St Albans City & District Council expects — so the back elevation answers the amenity case before a neighbour can lodge one. Two-storey rear extensions we draw with the 7-metre boundary gap and privacy screening resolved on the plan.
We draw rear extensions on every street in the borough. A few of the neighbourhoods where St Albans back-of-house projects come up most often:
Rear extension drawings for St Albans city centre's the medieval and Georgian historic core around the cathedral and Fishpool Street — depth-checked, daylight-tested and drawn to St Albans City & District Council's guidance.
Rear extension drawings for Harpenden's affluent commuter town of Edwardian and interwar semis and detached houses — depth-checked, daylight-tested and drawn to St Albans City & District Council's guidance.
Rear extension drawings for Marshalswick's interwar and postwar St Albans suburb of detached houses and semis — depth-checked, daylight-tested and drawn to St Albans City & District Council's guidance.
Rear extension drawings for Redbourn's historic village with a large common, period cottages and modern infill — depth-checked, daylight-tested and drawn to St Albans City & District Council's guidance.
Rear extension drawings for Wheathampstead's historic village between St Albans and Harpenden — depth-checked, daylight-tested and drawn to St Albans City & District Council's guidance.
Rear extension drawings for London Colney's large village with mixed twentieth-century estate housing — depth-checked, daylight-tested and drawn to St Albans City & District Council's guidance.
How far you can extend at the back in St Albans depends on your house type and the route you take. This is how the options compare.
| Route | Depth allowed | Consent needed | What St Albans City & District Council checks |
|---|---|---|---|
| Standard permitted development | 3m terrace/semi · 4m detached | Lawful development certificate (optional) | Depth, 4m height, materials |
| Larger-home prior approval | 6m terrace/semi · 8m detached | Prior-approval notice + neighbour consultation | Neighbour objections on amenity |
| Full householder application | Beyond the above, or two-storey | Full planning permission | Daylight (45°/25°), bulk, garden retained |
| Conservation area | Case by case | Full planning permission | Character, roof form, boundary treatment |
The larger-home route is switched off on designated land — conservation areas such as St Albans city centre and Fishpool Street and Article 4 streets need a full application.
A fixed process built around how St Albans City & District Council validates and decides rear-extension applications — most drawings are submission-ready within seven days of survey.
Send us your St Albans postcode and house type. We confirm your conservation and Article 4 status, how much rear-extension depth you have under permitted development, and score your odds against live St Albans City & District Council decisions.
We measure the original rear wall, floor and eaves levels, side and rear boundary distances and the neighbours' window positions — the numbers the depth limit and daylight splays depend on.
Chartered designers develop the single or two-storey rear extension to your brief, drawn inside the permitted-development limits or to St Albans City & District Council's extension design guidance, with the daylight angles shown.
We submit the certificate, prior-approval notice or application, handle validation and case-officer queries, and revise the drawings free until St Albans City & District Council issues its decision.
Often not. 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 involve St Albans City & District Council for anything deeper via the larger-home route, for two-storey rear extensions, and for any rear extension in a conservation area such as St Albans city centre and Fishpool Street, where those permitted-development rights fall away.
The larger-home extension scheme lets a single-storey rear extension reach 6 metres on a terrace or semi, or 8 metres on a detached house — double the standard allowance. It is not automatic: you submit a prior-approval notification to St Albans City & District Council, neighbours are consulted, and if one objects on amenity grounds the council rules on it. It also does not apply on designated land such as St Albans's conservation areas.
It is the daylight test St Albans City & District Council applies to protect neighbours. Drawn on plan, a line at 45 degrees from the midpoint of the neighbour's nearest ground-floor window should not be crossed by your extension; a companion 25-degree line is checked in section. If the projection breaches it, the extension is likely to be shortened or refused, so we test and prove it on the drawings before submission.
A two-storey rear extension almost always needs a full householder application to St Albans City & District Council, as it sits outside permitted development on most homes. The council checks that it stays at least 7 metres from the rear boundary, does not overbear the neighbours and avoids new overlooking. We resolve the boundary gap, privacy and daylight on the plans so the application is decided on its merits.
Frequently, yes. If the rear extension involves work to a shared wall, building up to the boundary, or excavating foundations near a neighbour's structure, the Party Wall etc. Act applies and you must serve notice — this is separate from St Albans City & District Council's planning decision. We flag it early and can prepare the drawings a party-wall surveyor needs alongside the planning set.
We price each St Albans rear extension on its own footprint and send a fixed, no-obligation quote within one working day. It covers the full drawing pack with free revisions until St Albans City & District Council approves, and we confirm at the outset whether your extension is permitted development, needs prior approval, or a full application. Call 020 7864 7245 to begin.
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.