The Roby Mill extension appeal has succeeded after a Planning Inspector decided that an objection from a parish council did not trigger the neighbour-amenity prior approval procedure. The decision, issued on 11 November 2026, concerns an eight-metre single-storey rear extension at a house in Up Holland, West Lancashire.
West Lancashire Borough Council had refused the application on several grounds. It questioned whether the plans genuinely showed a single-storey extension, whether an external stepped path breached the Class A limits and whether the excavation was substantial enough to need its own planning permission. Up Holland Parish Council had also objected to the proposal.
The Roby Mill extension decision matters beyond this one house because it separates two questions that are often confused: whether an extension qualifies as permitted development at all, and whether a qualifying larger rear extension needs an additional assessment of its effect on adjoining neighbours. The Inspector found in favour of the homeowner on both questions.
Why the Roby Mill extension counted as one storey
The proposal was for a rear addition extending eight metres beyond the original house, with a height of three metres. It followed the larger home extension procedure under Part 1, Class A, paragraph A.4 of the Town and Country Planning (General Permitted Development) (England) Order 2015. Our guide to larger home extensions explains the depth limits and the separate notification procedure in England.
The dispute arose because the garden slopes away from the original dwelling. The submitted drawings included a staircase and placed the proposed extension at a lower level than the main house. The Council argued that this meant the proposal amounted to a two-storey extension and fell outside the relevant permitted development limitations.
Inspector R Major disagreed. The stairs, which would connect the extension to the original house, would sit predominantly within the original dwelling’s footprint, and the accommodation inside the proposed extension would all be on one level. The fact that a new room would sit lower than the original floor level did not make the addition two storeys. The Roby Mill extension therefore satisfied the disputed single-storey requirements in paragraphs A.1(g) and A.1(h).
That finding was specific to the layout shown. A staircase is not automatically irrelevant to the number of storeys in an extension, and applicants still need to demonstrate what forms part of the enlarged house. The proper assessment is of the actual building and the proposed works, rather than the presence of stairs on a drawing by itself.
Separate steps and the Class A side-extension limits
The plans also showed an external stepped path beside the extension. The Council treated it as part of the proposed enlargement and argued that the scheme consequently extended beyond a side wall of the original house and exceeded the permissible width limits under paragraphs A.1(j) and A.1(ja).
The appellant said the path had only been included on the plans for clarity. Inspector Major agreed that the external steps, outside both the proposed extension and the original dwelling, were separate from the enlargement being considered. On that basis, the extension did not breach those particular restrictions.
It is important not to turn this into a general ruling that all paths and steps benefit from Class A. Their planning status can require a separate assessment. What the Inspector decided was that these steps were not themselves an enlargement of the dwellinghouse and did not enlarge the proposal under this particular prior approval application.
Excavation and the Eatherley judgment
A further issue was excavation. The Council relied on R (on the application of Michael Eatherley) v London Borough of Camden and James Ireland [2016] EWHC 3108 (Admin), a High Court decision about the difference between building works authorised by Class A and engineering operations capable of amounting to a separate activity of substance.
That judgment does not mean every excavation associated with an extension must be the subject of a separate planning application. Whether excavation is a distinct operation of substance requires a judgment on the actual works. A basement involving substantial excavation and structural supports is not necessarily comparable to ordinary foundation or ground works for a rear extension.
The Inspector considered the excavation needed for the Roby Mill extension to be a normal part of constructing a single-storey addition of this size. It was not a separate activity of substance on these facts. Consequently, the proposed addition could be assessed as a single operation falling within the permitted development right.
That is a useful distinction for sloping sites, although the amount and character of engineering work still matter. Applicants should not assume the conclusion would be identical for a deep excavation, major retaining structures or a materially different scheme. Planning Geek’s basement planning guidance sets out why the engineering-operation question is often decisive.
Why the parish council objection did not trigger prior approval
The second principal question was procedural. Under paragraph A.4(7), where an owner or occupier of adjoining premises objects, the local planning authority must consider the impact on the amenity of those adjoining premises. The wording does not give every person or public body who comments the same statutory position.
Up Holland Parish Council was the only objector. West Lancashire told the Inspector that the parish council leased a play area across the road, but no plan had been provided showing its extent. The parish council subsequently confirmed that it did not own adjoining land. The Inspector did not have sufficient evidence that it was an owner or occupier of any adjoining premises.
The Inspector said there was no substantive evidence before me
establishing that status. Although the Council suggested the parish council had spoken for concerned residents, the objection itself did not identify qualifying adjoining owners or occupiers, and no other objections had been submitted.
Accordingly, the objection did not engage paragraph A.4(7), so prior approval of the impact on adjoining amenity was not required. The Roby Mill extension appeal is a reminder that a parish council can make representations and raise legitimate concerns, but it cannot necessarily trigger the particular neighbour-amenity test reserved by the legislation for adjoining owners or occupiers.
For an authority handling these notifications, the practical question is not simply whether an objection has arrived. It is who has objected, what premises they own or occupy, and whether those premises are adjoining in the circumstances. Our prior approval guide explains why the statutory matters that can be considered vary between permitted development classes.
Another extension was already being built
There is an important factual qualification. At the Inspector’s site visit on 2 November, construction of a rear extension was under way. The appellant confirmed that this was a different, later approved scheme, identified in the appeal decision as application 2026/0343/PNH. The Inspector accepted that the eight-metre proposal under appeal had not commenced.
The allowed appeal must therefore not be described as retrospective permission for the works already under construction. The decision was about the earlier application 2026/0122/PNH and the eight-metre design on its submitted drawings. It does not prove that the separately authorised scheme has been built correctly or that every future amendment is permitted development.
What the Roby Mill extension decision means
The outcome was an allowed appeal with a finding that the submitted scheme met the relevant Class A limitations and did not need neighbour-amenity prior approval. Standard requirements under paragraphs A.3 and A.4 continued to apply. The Inspector did not grant an unrestricted planning permission or decide the merits of some different extension design.
The Roby Mill extension decision offers three practical lessons. Assess the actual storeys created rather than treating every internal step as a second storey; distinguish ordinary construction excavations from separate engineering operations; and check that an objection is made by a qualifying adjoining owner or occupier before invoking the neighbour-amenity process.
Appeal 6011238 was decided on 11 November 2026 by Inspector R Major, following a site visit. The brief quotation above is from the Planning Inspectorate’s decision under the Open Government Licence.
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