Two-storey extension drawings for St Denys homes — bedroom above, living space below, drawn against the 3-metre projection and 7-metre boundary rules and to Southampton City Council's design guidance, delivered in days and revised free until your decision.
Southampton City Council granted 92% of the householder planning decisions it made in its latest published year — 5 points above the 87% England-wide householder average. HMO concentration control keeps student conversions in check as the Portswood market pushes south, which is where a policy-literate drawing pack earns its keep. Its dominant Victorian (1837–1901) and Edwardian (1901–1910) 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 Denys carries at least one Article 4 direction, and conservation areas including Portswood Residents' Gardens and Itchen Valley remove those rights outright, so we confirm your exact address before a line is drawn. A validated householder application in St Denys is determined against an 8-week statutory target.
St Denys (Victorian terraces on the slope down to the tidal River Itchen), Adelaide Road (Edwardian terraces around the St Denys railway station), Priory Road (riverside terraces facing the Itchen and Riverside Park), Portswood border (student terraces shading up towards Portswood Broadway), Bitterne Park border (terraces near Cobden Bridge and the river crossing) and Kent Road (tightly packed Victorian terraced streets) — these are the St Denys pockets our drawings cover most. Heritage designations here include Portswood Residents' Gardens and Itchen Valley. Southampton City Council weighs each proposal against the Southampton City Local Plan / Core Strategy, where the tidal River Itchen and Riverside Park frontage bring flood-risk and green-setting tests into riverside schemes. Many St Denys terraces are split into flats or HMOs, so householder permitted-development rights rarely apply.. On roofs the borough is pitched slate roofs with rear slopes on the terraces and gabled roofs on the Edwardian rows, over Victorian and Edwardian bay-fronted terraces, converted terraced flats and HMOs and riverside housing along the tidal Itchen.
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. St Denys is largely Victorian and Edwardian bay-fronted terraces, converted terraced flats and HMOs and riverside housing along the tidal Itchen, and pitched slate roofs with rear slopes on the terraces and gabled roofs on the Edwardian rows 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.
HMO concentration control keeps student conversions in check as the Portswood market pushes south. St Denys is a compact riverside district next to Portswood, so the city-wide HMO Article 4 direction adopted in March 2012 applies and the right to convert a home to a small HMO has been removed to manage the spread of student housing from Portswood.
Some two-storey rear extensions are permitted development. You will need a full application to Southampton City 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 Southampton City Council checks first — then submit a validation-complete pack.
Below is Southampton City Council's real householder decision record, drawn from official planning statistics and refreshed as new data lands. Southampton approves around 92% of applications, and in St Denys the twin pressures of HMO concentration and the Itchen flood plain shape most schemes. 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 St Denys, Adelaide Road and Priory Road, 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 victorian and edwardian bay-fronted terraces, 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 tidal River Itchen and Riverside Park frontage bring flood-risk and green-setting tests into riverside schemes. 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 St Denys. A few of the areas where they come up most often:
Two storey extension drawings for St Denys — Victorian terraces on the slope down to the tidal River Itchen — dimensioned against the 3m and 7m limits and drawn to Southampton City Council's guidance.
Two storey extension drawings for Adelaide Road — Edwardian terraces around the St Denys railway station — dimensioned against the 3m and 7m limits and drawn to Southampton City Council's guidance.
Two storey extension drawings for Priory Road — riverside terraces facing the Itchen and Riverside Park — dimensioned against the 3m and 7m limits and drawn to Southampton City Council's guidance.
Two storey extension drawings for Portswood border — student terraces shading up towards Portswood Broadway — dimensioned against the 3m and 7m limits and drawn to Southampton City Council's guidance.
Two storey extension drawings for Bitterne Park border — terraces near Cobden Bridge and the river crossing — dimensioned against the 3m and 7m limits and drawn to Southampton City Council's guidance.
Two storey extension drawings for Kent Road — tightly packed Victorian terraced streets — dimensioned against the 3m and 7m limits and drawn to Southampton City 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 Southampton City 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 Southampton City Council validates and decides two-storey applications.
Send us your St Denys postcode and garden depth. We measure the 7-metre boundary rule against your plot, confirm designation status, and score your odds against live Southampton City 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 Southampton City 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 St Denys, the 7-metre rule is what most commonly forces a full application to Southampton City 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 St Denys gardens this is decisive, and we measure it on survey before any design work rather than discovering it at validation. Southampton City Council is the decision-maker.
Not under permitted development — two-storey side extensions always need a full application to Southampton City 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 St Denys 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 St Denys address specifically. Southampton City 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 Southampton City Council's planning decision, so we flag the notice period early and detail the junction on the drawings. This applies to your St Denys 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 St Denys address specifically. Southampton City Council is the decision-maker.
We quote each St Denys 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 Southampton City Council approves. Call 020 7864 7245 to start.
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