Document bundle for a rear dormer in a conservation area

A rear dormer on a house in a conservation area needs planning permission. The permitted development right for roof enlargements is withdrawn on article 2(3) land, so there is no way to build one without applying. The bundle is a householder application with a specific drawing set: existing and proposed roof plans, rear and side elevations, a section through the dormer, a contextual elevation showing the neighbouring roofs, a materials and window schedule, and a short heritage statement explaining the effect on the character of the area.

A design and access statement is usually not required for work of this size, which surprises people. The requirement in conservation areas applies to development creating one or more dwellings or a building with 100 square metres or more of floorspace, and a dormer is neither.

Why permitted development is unavailable here

Class B of Part 1 of Schedule 2 to the General Permitted Development Order 2015 permits the enlargement of a house consisting of an addition or alteration to its roof, which is the class a dormer would normally rely on. Class B is not permitted on article 2(3) land.

Article 2(3) land covers conservation areas, National Landscapes, National Parks, the Broads and World Heritage Sites. So in a conservation area the question is not whether your dormer fits the Class B limits. It is a planning application either way.

For context, had the house been outside a conservation area, Class B would have allowed a dormer within a volume allowance, set back at least 20 centimetres from the original eaves, no higher than the highest part of the existing roof, and not extending beyond the plane of the roof slope forming the principal elevation where that fronts a highway. Those parameters are still worth knowing, because a design that would have satisfied Class B is a sensible starting point for a scheme the council can accept.

Article 4 directions can withdraw further rights in a conservation area, so check the authority's register for the address before assuming anything else is permitted either.

The application type and the forms

This is a householder application, submitted with the standard forms, a fee set by the national fee regulations and indexed annually, so check the current schedule. The ownership certificate has to be completed, and the agricultural holdings declaration signed.

The site location plan should be at a recognised scale with the application site edged red and any other land in the applicant's ownership edged blue. A block plan showing the house and its boundaries is normally required by local lists even where the national requirements do not demand one.

Check the local validation list. It is where the extra requirements live, and for conservation area work those commonly include photographs of the host building and the street, a roof plan, and a materials schedule. Our note on conservation area application documents covers the general pattern across application types.

Drawings including roof plans and street elevations

The drawing set is the application. An officer assessing a dormer is assessing proportion, position and detail, and all three are read from the drawings.

What to include:

1. Existing and proposed roof plans, showing the dormer position relative to the ridge, eaves, party walls and any chimney.
2. Existing and proposed rear elevation at a consistent scale, with dimensions for the dormer width, height and set-backs.
3. Existing and proposed side elevations, which show how the dormer reads from an angle.
4. A section through the dormer showing the internal head height and the relationship to the roof pitch.
5. A contextual rear elevation showing at least the two houses either side, so the officer can see whether the dormer follows an established pattern.
6. Detail drawings of the window head, cill and cheek construction at a larger scale.

The contextual elevation is the drawing most often omitted and the one that most often wins the application. Where neighbouring roofs already carry dormers of similar proportion, showing that on a single drawing answers the character question more effectively than two paragraphs of text.

Set-backs matter. A dormer set down from the ridge and in from the party walls reads as subordinate to the roof. One that runs the full width and touches the ridge reads as an extra storey, and that is the usual reason for refusal.

Heritage evidence proportionate to a small scheme

A Heritage Statement for a dormer should be short. Two or three pages, covering the conservation area and its character, the contribution the host building and its roofscape make, the effect of the dormer, and why the design responds.

Use the authority's conservation area appraisal where one exists. It will describe the character of the area and often identifies roofscape, materials or uniformity as features of interest, and quoting the appraisal's own words is more persuasive than your assessment of the same thing.

The statutory duty is the one in the listed buildings and conservation areas legislation: to pay special attention to the desirability of preserving or enhancing the character or appearance of the conservation area. Address that test in terms, because the officer has to.

Where the house is listed as well as in a conservation area, the position changes entirely: listed building consent is needed in addition to planning permission, and the drawing and heritage requirements step up considerably.

Amenity evidence for the neighbours

A new rear dormer usually adds a window at a level that looks into neighbouring gardens and, on a tight terrace, into neighbouring rear windows.

Deal with it on the drawings rather than waiting for an objection. Show the window position and the distance to the nearest boundary and the nearest facing window. Where overlooking is close, consider a higher cill, obscure glazing to part of the opening, or a narrower window placed away from the boundary.

Where loss of light to a neighbour could be in issue, which is less common for a rear dormer than for a ground-floor extension, say so and explain why the dormer does not cause it. A short paragraph on the geometry is usually enough, and it heads off a request for a daylight assessment.

Do not forget the roof terrace question. A dormer with a flat roof invites the thought of access onto it, and an officer may ask for a condition preventing use as a terrace. Offering that condition yourself removes the issue.

Materials information the officer will ask for

Specific is better than "to match". A schedule naming each element, its material, finish and colour, cross-referenced to the elevations, prevents a request for further information.

Cover the dormer cheeks and front face, the roof covering over the dormer, the window frame material and opening type, the glazing, the flashings and the rainwater goods. In most conservation areas the acceptable palette is narrow: lead or zinc cheeks rather than tile, slate or tile to match the main roof, timber or slim metal frames rather than thick plastic sections, and windows set back in a reveal rather than flush with the face.

Offer samples where the authority's own guidance asks for them, and be prepared for a condition requiring approval of samples before the relevant work starts.

Items local validation lists add

The additions vary, and the list is published, so read it. Common extras for this kind of application:

• photographs of the host building, the rear elevation and the wider street
• a roof plan, which is not always a national requirement
• a materials schedule or sample panel commitment
• a tree survey where protected trees stand close to the works, which our page on a Tree Survey describes
• a bat assessment where the roof is being opened up, since roof voids are common roost locations

That last one catches people. Where a roof is being stripped or a void opened, a precautionary assessment by a suitably licensed ecologist may be needed, and survey seasons for bats run from May to September. Finding that out in October costs a year.

This is general guidance, not legal advice; check the position with your local planning authority or a qualified professional before relying on it. Enter your postcode on PlanScope to see which of the 66 reports your project is likely to need. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.