Rear dormer drawings for Cornwall roofs — the box across the back slope that turns a low attic into a full-height room, drawn to Cornwall Council's guidance and the volume limits, delivered in days and revised free until your decision, with a free approval-odds check first.
Cornwall Council granted 97% of the householder planning decisions it made in its latest published year — 10 points above the 87% England-wide householder average. Cornwall contains BERRY TOWER, BODMIN, BODMIN, BOJEWYAN conservation areas (BERRY TOWER, BODMIN designated 1994), so materials, fenestration and roof form are assessed against the appraisal, which is where a policy-literate drawing pack earns its keep. Its dominant Victorian (1837–1901) 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 Cornwall Council needs a full application. In conservation areas such as BERRY TOWER, BODMIN, BODMIN and BOJEWYAN those rights are removed, so we confirm your exact address before a line is drawn. A validated householder application in Cornwall is determined against an 8-week statutory target.
BERRY TOWER, BODMIN (conservation area designated in 1994), BODMIN (conservation area designated in 1991), BOJEWYAN (conservation area designated in 2002), BOSCASTLE (conservation area designated in 1974), BOSCASWELL (conservation area designated in 2002), BOTALLACK & TRUTHWALL (conservation area designated in 2002), BUDE (conservation area designated in 1988), CADGWITH (conservation area designated in 1978), Bodmin St Petroc's (ward of Cornwall), Bude (ward of Cornwall), Camborne Trelowarren (ward of Cornwall), Camelford & Boscastle (ward of Cornwall), Falmouth Arwenack (ward of Cornwall), Feock & Kea (ward of Cornwall), Hayle West (ward of Cornwall) and Land's End (ward of Cornwall) — these are the Cornwall pockets our drawings cover most. Heritage designations here include BERRY TOWER, BODMIN, BODMIN, BOJEWYAN, BOSCASTLE, BOSCASWELL, BOTALLACK & TRUTHWALL, BUDE and CADGWITH. Cornwall Council weighs each proposal against Cornwall Council's development plan and the design policies it applies to householder applications, where the 83,150 homes here are 28% pre-1900, 7% 1965-1972, 6% 1973-1982, which is what sets the realistic roof and rear-projection options. On roofs the borough is steeply pitched slate roofs, valley gutters and party parapets typical of pre-1900 building and shallow-pitched roofs and integral garages typical of that period's building, over Victorian and earlier houses (28% of 83,150 homes), late-1960s and early-1970s houses (7%) and 1970s and early-1980s houses (6%).
Heritage designation is the single biggest variable in Cornwall, and it is address-specific: BERRY TOWER, BODMIN (conservation area designated in 1994), BODMIN (conservation area designated in 1991), BOJEWYAN (conservation area designated in 2002), BOSCASTLE (conservation area designated in 1974), BOSCASWELL (conservation area designated in 2002), BOTALLACK & TRUTHWALL (conservation area designated in 2002), BUDE (conservation area designated in 1988) and CADGWITH (conservation area designated in 1978). Inside those boundaries permitted development is curtailed and Cornwall 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, Cornwall takes in Bodmin St Petroc's, Bude, Camborne Trelowarren, Camelford & Boscastle, Falmouth Arwenack, Feock & Kea, Hayle West and Land's End. No Article 4 direction is recorded for Cornwall Council, but the district's 8 conservation areas still limit permitted development on those streets.
On stock, Cornwall is Victorian and earlier houses (28% of 83,150 homes), late-1960s and early-1970s houses (7%) and 1970s and early-1980s houses (6%) — which is why steeply pitched slate roofs, valley gutters and party parapets typical of pre-1900 building and shallow-pitched roofs and integral garages typical of that period's building govern what a loft or rear projection can realistically be. Cornwall Council decided 1,863 householder applications in the latest published year and granted 97%, with 76% issued inside the eight-week target. We work from the council's own published record.
The full build-period split for Cornwall runs pre-1900 3% (190 homes), 1900-1918 0% (30 homes), 1919-1929 0% (10 homes), 1930-1939 6% (350 homes), 1945-1954 3% (170 homes), 1955-1964 30% (1,850 homes), 1965-1972 33% (1,990 homes), 1973-1982 4% (260 homes), 1983-1992 5% (310 homes), 1993-1999 4% (220 homes) and 2000-2008 3% (170 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.
Cornwall Council also decides for Bodmin St Petroc's, Bude, Camborne Trelowarren, Camelford & Boscastle, Falmouth Arwenack, Feock & Kea, Hayle West and Land's End, so a decision in Cornwall 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 Cornwall and Cornwall Council. These are the numbers that decide what is realistic on your street, so we work from them rather than from national averages.
| Measure | Cornwall |
|---|---|
| Dwellings recorded | 83,150 |
| Built pre-1900 | 190 (3%) |
| Built 1900-1918 | 30 (0%) |
| Built 1919-1929 | 10 (0%) |
| Built 1930-1939 | 350 (6%) |
| Built 1945-1954 | 170 (3%) |
| Built 1955-1964 | 1,850 (30%) |
| Built 1965-1972 | 1,990 (33%) |
| Built 1973-1982 | 260 (4%) |
| Built 1983-1992 | 310 (5%) |
| Built 1993-1999 | 220 (4%) |
| Built 2000-2008 | 170 (3%) |
| Built before 1919 | 30% |
| Built 1919–1939 | 7% |
| Built 1945–2008 | 49% |
| Conservation areas in Cornwall | 8 (BERRY TOWER, BODMIN, BODMIN…) |
| Conservation areas district-wide | 145 |
| Article 4 directions recorded | 0 |
| Householder applications decided | 1,863 |
| Householder applications granted | 97% |
| Decided within 8 weeks | 76% |
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 Cornwall Council's own, from MHCLG live table PS2 for the year to 31 March 2026.
The box dormer is the workhorse loft, and most of Cornwall is built for it — the borough runs to Victorian and earlier houses (28% of 83,150 homes), late-1960s and early-1970s houses (7%) and 1970s and early-1980s houses (6%) under steeply pitched slate roofs, valley gutters and party parapets typical of pre-1900 building and shallow-pitched roofs and integral garages typical of that period's building, and a flat-roofed box across the rear slope is the cheapest cubic metre of full-height space those roofs give up. Cornwall Council tests the dormer against Cornwall Council's development plan and the design policies it applies to householder applications, and because permitted development turns on a number, the volume you propose against the volume you have left is the first thing an officer or a certificate checks.
That is why the arithmetic goes on the drawings. We calculate the box against the 40- or 50-cubic-metre allowance, count any earlier roof enlargement into the total, hold the flat roof below the ridge and set the face back off the eaves so the dormer reads as subordinate. Cornwall contains BERRY TOWER, BODMIN, BODMIN, BOJEWYAN conservation areas (BERRY TOWER, BODMIN designated 1994), so materials, fenestration and roof form are assessed against the appraisal, so the cheeks, the window line and the material are drawn to answer it rather than invite a query.
Where Cornwall's streets are protected — BERRY TOWER, BODMIN, BODMIN, BOJEWYAN, BOSCASTLE, BOSCASWELL, BOTALLACK & TRUTHWALL, BUDE and CADGWITH among them — the Class B dormer right is switched off and even a modest rear box needs consent. No Article 4 direction is recorded for Cornwall Council, but the district's 8 conservation areas still limit permitted development on those streets. We confirm the designation before the box is sized.
Many rear dormers in Cornwall are permitted development, but the volume and position decide it. You will normally need a full application to Cornwall Council if any of these apply:
We draw the box within its volume allowance, the flat roof below the ridge and the face set back off the eaves — the three things a dormer stands or falls on — and submit a validation-complete pack, whether that is a lawful development certificate or a full householder application.
Below is Cornwall Council's real householder decision record, drawn from official planning statistics and refreshed as new data lands. Cornwall Council granted 97% of 1,863 householder decisions in the year to 31 March 2026, 76% of them inside eight weeks. A dormer is decided on volume and set-back, so a pack that shows the calculation and the eaves detail is cleared 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 BERRY TOWER, BODMIN, BODMIN and BOJEWYAN, the dormer that goes through is the subordinate rear box: flat roof kept low, cheeks clad to recede, side windows obscure-glazed against overlooking, and the whole thing set back so the original eaves line still reads from the garden. On steeply pitched slate roofs, valley gutters and party parapets typical of pre-1900 building, this returns a full-height double and en-suite from what was standing-room-only, usually inside the permitted-development volume.
The 83,150 homes here are 28% pre-1900, 7% 1965-1972, 6% 1973-1982, which is what sets the realistic roof and rear-projection options. We keep the box off the ridge, match the cheek material to the roof, and where the volume is already spent — or the street is designated — draw the dormer as a householder application composed to Cornwall Council's roof-alteration guidance rather than push a certificate that would be refused.
We draw rear dormers on the terraced and semi-detached streets across the borough. A few of the neighbourhoods where Cornwall dormers come up most often:
Dormer loft drawings for BERRY TOWER, BODMIN's conservation area designated in 1994 — volume-checked, set-back-detailed and drawn to Cornwall Council's guidance.
Dormer loft drawings for BODMIN's conservation area designated in 1991 — volume-checked, set-back-detailed and drawn to Cornwall Council's guidance.
Dormer loft drawings for BOJEWYAN's conservation area designated in 2002 — volume-checked, set-back-detailed and drawn to Cornwall Council's guidance.
Dormer loft drawings for BOSCASTLE's conservation area designated in 1974 — volume-checked, set-back-detailed and drawn to Cornwall Council's guidance.
Dormer loft drawings for BOSCASWELL's conservation area designated in 2002 — volume-checked, set-back-detailed and drawn to Cornwall Council's guidance.
Dormer loft drawings for BOTALLACK & TRUTHWALL's conservation area designated in 2002 — volume-checked, set-back-detailed and drawn to Cornwall Council's guidance.
Whether a dormer in Cornwall needs permission comes down to where it sits and how big the box is. This is how the cases compare.
| Dormer type | Permitted development? | What it gains | What Cornwall Council checks |
|---|---|---|---|
| Rear box, within volume | Usually yes | Full-height room across the back | Volume total, 20cm eaves set-back |
| Rear box, over volume limit | No — full application | A larger room | How far over the allowance, bulk |
| Front or side dormer | No — full application | Light to the front rooms | Visibility from the street, character |
| Dormer in a conservation area | No — full application | Same space, extra scrutiny | Roof form and street appearance |
In conservation areas such as BERRY TOWER, BODMIN and BODMIN, Class B dormer rights are removed and every dormer needs a full application.
A fixed process built around how Cornwall Council validates and decides dormer applications — most drawings are submission-ready within seven days of survey.
Send us your Cornwall postcode and roof type. We confirm your conservation and Article 4 status, work out how much permitted-development volume you have left, and score your odds against live Cornwall Council decisions.
We measure ridge and eaves heights, roof pitch and the existing loft floor — the numbers the volume calculation, the set-back and the head heights depend on.
Chartered designers develop the box to your brief, drawn inside the Class B volume limits or, where those are exhausted or removed, to Cornwall Council's roof-alteration guidance.
We submit the certificate or application, manage validation and case-officer queries, and revise the drawings free until Cornwall Council issues its decision.
Often not. A rear box dormer within 40 cubic metres on a terrace, or 50 on a semi or detached house, set back at least 20 centimetres from the eaves and kept below the ridge, is usually permitted development. In Cornwall you will need a full application to Cornwall Council for a front or side dormer, a box that exceeds the volume, and any dormer in a conservation area such as BERRY TOWER, BODMIN and BODMIN, where those rights are removed.
The permitted-development limit is a volume, not a footprint: 40 cubic metres of added roof space on a terraced house and 50 on a semi-detached or detached one, and any earlier loft enlargement counts against that total. In Cornwall the box must also sit below the ridge and back from the eaves. We measure your roof and calculate the exact volume you have left before drawing. Cornwall Council is the decision-maker.
Not under permitted development. A dormer on the front roof slope, or one facing a highway, always needs a full application to Cornwall Council, because it changes how the house reads from the street. Rear box dormers are far more likely to be approved — or to be permitted development outright — which is why almost every Cornwall dormer we draw sits on the back slope.
Often, on a terrace or semi. If the dormer or the loft steelwork meets the party wall with your neighbour, the Party Wall etc. Act applies and notice must be served before work starts — separately from Cornwall Council's planning decision. We flag the party-wall junction on the drawings so a surveyor can be appointed early and the build is not held up.
If your dormer is permitted development, a lawful development certificate from Cornwall Council is council-stamped proof of it — worth holding, because a buyer's solicitor will ask for it when you sell. We prepare and submit the certificate with the same measured drawing pack that shows the box within its volume allowance.
We price each Cornwall dormer individually, because the roof pitch and the volume left vary house to house, and send a fixed, no-obligation quote within one working day. It covers the full drawing pack with free revisions until Cornwall Council approves, and we confirm at the outset whether your box is permitted development or needs an application. Call 020 7864 7245 to start.
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