A new outrigger dormer appeal in Harwich, Essex, has failed after a Planning Inspector decided that the proposed enlargement was not simply a roof conversion. Although the drawings called it an L-shaped dormer, significant work above the house’s lower rear wing was instead assessed as a house extension under Class A of permitted development.
Inspector R Bartlett dismissed the certificate of lawfulness appeal on 29 October 2026 at Talbot Street, following Tendring District Council’s refusal in November 2024. The scheme involved a three-storey end-of-terrace house with a much lower, two-storey rear outrigger and proposed building work at second-floor level.
The outrigger dormer appeal matters beyond one property because homeowners often assume that joining a dormer to a rear wing automatically brings all the work within Class B. I would start by identifying which existing roof is being altered, what the new structure actually does and where its usable accommodation sits, rather than relying on the label used on the drawings.
An outrigger dormer appeal with two different operations
The application sought a certificate under section 192 of the Town and Country Planning Act 1990 for a proposed loft conversion with an L-shaped dormer. A certificate asks whether the works would have been lawful at the application date, not whether an Inspector finds the appearance or wider planning merits acceptable.
The main dwelling already had upper-floor rooms partly within its shallow roof. The proposed rear dormer on that main roof would not, on the drawings, create additional usable accommodation within the existing main-roof space. Access would remain through a loft hatch, while the existing trusses were shown as retained.
The original rear outrigger was substantially lower than the main house and shared a pitched roof with the neighbouring property. Above it, the proposal would add accommodation at the level of the main house’s second floor, entered through a new opening in the rear wall rather than through the existing outrigger roof.
That factual difference was central. The Inspector concluded that the higher rear-wing element was better understood as a separate enlargement of the dwelling. Describing the combined outline as an L-shaped dormer did not establish that every component was roof development.
Why the Inspector separated Class A and Class B
Class B of Part 1 of Schedule 2 to the General Permitted Development Order allows qualifying enlargements consisting of additions or alterations to the roof of a dwellinghouse. Class A concerns qualifying enlargements, improvements and other alterations to the dwellinghouse itself. They are separate routes with different tests and limitations.
In this outrigger dormer appeal, the rear-wing proposal would add effectively another storey while using very little of the roof space already there. Its flat roof would sit substantially above the existing rear-wing eaves and ridge, as well as above the main house’s eaves.
Inspector Bartlett said that this goes well beyond an enlargement consisting solely of an addition or alteration to a roof
. The quotation comes from paragraph 8 of the official Planning Inspectorate decision, reproduced under the Open Government Licence v3.0.
The main-roof dormer and the upward extension over the outrigger were physically connected, but the Inspector found they were at materially different heights, on different floors and without an internal connection between the two parts. The result was not one continuous enlargement joining two usable roof spaces.
Why the proposed work was not permitted development
The extension above the outrigger failed several Class A limitations. These included the eaves-height requirements, the special limit where enlarged eaves would be within two metres of the curtilage boundary, and the prohibition on altering the roof of the dwellinghouse through Class A.
The Inspector also concluded that the dormer on the main roof, linking through the eaves and beyond the rear wall to the upper rear-wing extension, failed the relevant Class B requirements. The decision does not mean that all L-shaped dormers are prohibited, only that these particular drawings did not satisfy the applicable permitted development classes.
The outrigger dormer appeal was therefore dismissed. Tendring’s refusal of the proposed certificate, application 24/01555/LUPROP, was upheld. The Inspector did not decide an application for planning permission for the same design, and there was no assessment of whether a revised scheme might secure permission.
For householders and designers, it is important not to treat a successful roof-volume calculation as the whole answer. The geometry and construction of the proposed works, including wall openings, new floors, original rooflines and the relationship between the rear wing and main roof, may determine which permitted development class must be applied.
Other dormer decisions do not create an automatic rule
The appellant supplied three earlier appeal decisions, but the Inspector considered them materially different. Those proposals involved single joined extensions or alterations with comparable floor and roof levels. One earlier appeal, APP/K3605/X/23/3316515, was cited as supporting the distinction where works amounted to an additional storey over an outrigger.
Planning Geek’s existing outrigger dormer permitted development guide examines decisions where Inspectors have accepted roof enlargements under Class B, alongside cases in which the scheme was properly treated as a separate Class A extension. Some connected dormers can qualify; others cannot.
This outrigger dormer appeal adds a useful new factual example rather than announcing a universal prohibition. The essential question is whether the rear-wing work is a genuine roof enlargement, a separate upward extension to the house, or a combination of operations that must independently meet different legal limits.
What to check before submitting a lawful development certificate
An accurate existing-and-proposed section is as important as the elevation drawings. Mark the original eaves, ridge, internal floor heights and the proposed access route. Where an outrigger is lower than the main roof, explain whether the design enlarges existing roof space or creates an additional storey above the rear wing.
The Class B roof enlargement guide explains the dormer limitations, including volume and the position of additions relative to the existing roof. The Class A tests should also be assessed wherever the project changes the walls or overall height of a rear projection rather than simply enlarging its roof.
Before committing to work, a proposed certificate of lawfulness can confirm a carefully specified design. But the plans must show the operations that will actually be built, and the burden remains on the applicant to demonstrate lawfulness on the relevant date.
The lesson from the outrigger dormer appeal is practical. A label such as ‘loft conversion’ does not convert a new upper storey into permitted roof development. If the proposal crosses from one class into another, a more careful redesign or an ordinary planning application may be required.
Decision details and original sources
The decision was issued by Inspector R Bartlett on 29 October 2026 for APP/P1560/X/25/3364647, Talbot Street, Harwich. Read the official Planning Inspectorate appeal case. The original decision also discusses three earlier Inspector appeals; these are planning appeal decisions, not court judgments.
The appeal decision is also available on AppealBase. For this outrigger dormer appeal, the critical outcome was a refusal to certify lawfulness because the particular upward rear-wing enlargement and associated dormer failed the permitted development requirements.
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