Larger rear extension refused at prior approval: next steps

A refusal of prior approval for a larger home extension is not a refusal of planning permission, and that distinction matters because it shapes what you do next. Under Class A of Schedule 2 Part 1 to the GPDO 2015, a rear extension deeper than the basic allowance can be built if the neighbour consultation scheme is followed and the authority gives prior approval. Where a neighbour objects, the authority must consider the impact on the amenity of adjoining premises, and if it concludes the impact is unacceptable it refuses. The scheme then falls outside the class entirely.

Three routes remain: reduce the depth to the basic allowance and build without any approval, apply for full planning permission, or appeal the refusal. Which one is right depends on what the refusal actually said.

What the prior approval decision can consider

The neighbour consultation scheme is narrow by design. Where an adjoining owner or occupier objects within the 21-day period, the authority must consider the impact of the proposed development on the amenity of all adjoining premises, and that is the whole of its remit.

What that excludes is as important as what it includes. The authority cannot refuse because it dislikes the design, because the materials are not matching in its view, because parking is tight or because the scheme would set a precedent. It cannot impose conditions beyond those in the Order. And it cannot consider the impact on premises that are not adjoining, so an objection from three doors away carries no weight in the assessment even if it is logged.

So the refusal notice should state an amenity effect on an adjoining property. If it states something else, that is the ground on which an appeal is most likely to succeed.

Why neighbour objections trigger an assessment

Without an objection there is no assessment. The authority notifies the adjoining owners and occupiers, and if none objects within 21 days the authority must grant prior approval, or the development may proceed once the 42-day determination period expires without a decision.

One objection changes the position entirely, and it does not need to be well reasoned. The statutory trigger is the receipt of an objection from an adjoining owner or occupier, not the merit of it. The authority then forms its own view on amenity impact, and it can grant approval despite the objection, which it frequently does.

The 42-day point is worth watching. Where the authority has failed to determine within the period, the development may proceed, and keeping a dated record of the notification and the acknowledgement is what lets you rely on it.

The amenity grounds officers rely on

In practice, refusals cite one or more of a short list, and knowing them tells you what to change.

Loss of light to a habitable room window, usually a rear-facing kitchen or living room, assessed by eye or by a 45-degree test taken from the centre of the neighbour's nearest window at ground floor level. Overbearing effect, where a 3m high flank wall runs 6m along a boundary close to a neighbour's patio doors. Enclosure of a small garden or light well. And loss of outlook, where the extension occupies most of the view from a ground-floor window.

Terraced and small semi-detached houses are where these arguments have force, because the separation distances are short and rear windows face each other across narrow gardens. A 6m extension on a detached house with a 3m side gap is rarely refused on amenity grounds. The same 6m on a mid-terrace with a neighbour's single-storey kitchen on the boundary frequently is.

Read the refusal closely. If it refers to a 45-degree assessment, you can test the figures yourself from the drawings, and a reduction in depth or an eaves height reduction along the boundary often brings the scheme within the threshold.

Reducing the depth to the basic allowance

The simplest route is to drop back to the depth that needs no approval at all. Under Class A the basic allowance for a single-storey rear extension is 3m beyond the rear wall of the original dwellinghouse for a terraced or semi-detached house and 4m for a detached house, subject to all the other Class A limits and conditions.

That route has real advantages. It requires no application and no further decision, there is no fee, and the neighbour has no further say. It also removes the risk of the authority looking at other aspects of the scheme.

Check every other Class A limit before relying on it, because a prior approval refusal sometimes reveals that the scheme had other problems. In particular the height limits, the 50 per cent coverage test under A.1(b), the restriction on development forward of the principal elevation and the additional restrictions on designated land. Our note on the 50 per cent curtilage test on a subdivided plot covers the test that most often bites after a plot has changed shape.

Where the lost depth matters, consider whether the space can be recovered elsewhere. A side infill within the Class A limits, or a modest reduction in depth combined with a wider opening to the existing rear room, sometimes delivers the same internal arrangement.

Applying for full permission instead

A full householder application is assessed on the development plan and all material considerations, which cuts both ways. The authority can consider design and the street scene, which it could not before. But it can also impose conditions, accept mitigation and grant permission for a scheme the Order would not permit, and it must weigh the benefits as well as the harm.

A householder application is usually the right route where you want more than the prior approval scheme offered, where the site has a constraint that puts it outside Class A anyway, or where the amenity harm can be mitigated by design rather than by depth. Mitigation that works:

• setting the extension in from the shared boundary by 500mm to 1m
• reducing the eaves height along the boundary and pitching the roof away from the neighbour
• using a flat roof with a parapet rather than a mono-pitch rising towards the boundary
• obscure glazing and no openings in the flank elevation
• a rooflight arrangement that keeps the mass down

Support it with a short planning statement that addresses the council's householder design guide, gives the 45-degree assessment result and separation distances, and explains what has changed since the prior approval refusal. An application that ignores the earlier refusal reads badly.

Appealing a prior approval refusal

A refusal of prior approval can be appealed to the Planning Inspectorate. For householder development the householder appeal service applies, with a 12-week deadline from the date of the decision notice and a short written procedure.

Appeal where the refusal is legally wrong rather than where you merely disagree with the amenity judgement. The strong grounds:

1. The refusal cites matters outside the authority's remit, such as design, materials, parking or precedent.
2. The objection came from premises that are not adjoining.
3. No valid objection was received within the 21-day period.
4. The authority failed to follow the notification procedure in the Order.
5. The amenity assessment is unsupported, for example a loss of light conclusion with no assessment behind it.

Appealing a straightforward amenity judgement on a mid-terrace, where the inspector is likely to reach the same view, usually costs twelve weeks for nothing. The honest position is that inspectors give weight to a reasoned local assessment of amenity, and overturning one needs more than an assertion that the neighbour is being unreasonable.

What to change before you resubmit

If the refusal is a sound amenity judgement, change the thing it objected to and resubmit rather than argue.

Work through this sequence. Identify the specific adjoining property and window named in the refusal. Measure the separation distance and run the 45-degree test from that window yourself. Reduce the depth, the height on the boundary, or both, until the test is passed, and show the calculation on the drawing. Add the set-in from the boundary if there is room. Then decide whether the revised scheme fits within the basic Class A allowance, in which case build it, or still needs prior approval, in which case notify again.

There is no limit on the number of prior approval applications you can make, and the fee is modest. A second notification with a 4m extension and a reduced boundary eaves height, after a 6m refusal, is often granted without objection, because the neighbour's actual concern has been met. Our notes on front garden paving and Class F and on garden offices and the separate planning unit problem cover the other householder rights worth checking while the drawings are open.

This is general guidance, not legal advice. Check the position with your local planning authority or a qualified professional before relying on it. A lawful development certificate is the only formal way to confirm that works are lawful.