Land west of Underlane, Carnkie, Wendron (mushroom growing building)

Decision

dismissed, 2 October 2026

Decided by

Planning Inspector: S Harrington

Authority

Cornwall (South West)

Appeal reference

6008292

Application reference

PA25/06342

Procedure

written representations

Development

Agricultural building for growing and storing mushrooms, with hardstanding and access already laid (part retrospective)

Site context

open countryside

Green Belt

No

Framework applied

August 2026 NPPF

Determinative policies

N2(1)(a), BNG (Sch 7A TCPA), s38(6)

Development plan policies

Cornwall Local Plan Strategic Policies 2010-2030 Policies 1, 2, 5, 12, 23, Climate Emergency DPD 2023 C1, G2

Main issues

character and appearance; biodiversity net gain

Summary

A stand-alone building for growing mushrooms in open countryside near Carnkie was dismissed. The inspector found significant harm to the landscape from an isolated, eye-catching building, and could not be sure the biodiversity net gain baseline was accurate because it left out hardstanding laid in 2024. Agricultural development is supported by S5(1)(a) and domestic food production attracts substantial weight, but the benefits were thinly evidenced and "likely to be modest". The appeal was decided on the development plan, whose policies were given substantial weight as consistent with the Framework.

Issues and findings

• Transition. The parties had the opportunity to comment on the revised Framework (DL ¶3).
• Landscape, N2: CONFLICT. "the scale of the building would be a visually intrusive and incongruous feature resulting in significant harm to the landscape value of the area" (DL ¶13). "the proposal would be contrary to the provisions of Framework Policy N2, which seeks to improve the natural environment" (DL ¶25).
• Biodiversity net gain: NOT SHOWN. "I cannot be sure that the BNG documentation before me provides an accurate baseline" (DL ¶18).
• Need for this location. "I have insufficient evidence to demonstrate there is an overriding locational and business need for the proposal to be in the location of the appeal site" (DL ¶21).
• S5(1)(a). "Framework Policy S5 supports development outside of settlements for agriculture horticulture or forestry, unless the benefits of doing so would be substantially outweighed by any adverse effects." (DL ¶22).
• Food production, E2 and E4. "in giving substantial weight to the benefits for domestic food production, I find such benefits are likely to be modest" (DL ¶24).
• Plan weight. "given the relevant policies consistency with the Framework and the level of harm identified, I afford substantial weight" (DL ¶25).

Planning balance

Plan-led. The S5(1) test is stated (DL ¶22) but the letter never concludes on it. Instead the modest benefits are set against the N2 conflict and the development plan conflict at substantial weight, and the appeal is dismissed under section 38(6) (DL ¶25, ¶27).

What made the difference

An isolated building in an exposed landscape, with no farmstead to group with and no evidence that the business needed this site. The biodiversity gain failure was self-inflicted: the hardstanding was laid before the baseline was taken. Siting beside existing buildings, a business case with contracts and income, and a baseline that accounted for the earlier works would each have been needed.

Transferable points

• S5(1)(a) support for agricultural development does not prevent refusal where landscape harm is significant and the development plan, consistent with the Framework, points the other way (DL ¶22, ¶25).
• E2 substantial weight for domestic food production attaches to benefits that are demonstrated; unevidenced benefits were "likely to be modest" (DL ¶24).
• Works carried out before the biodiversity baseline is measured require degradation information; without it the baseline cannot be relied on (DL ¶16-18).
• A local policy test of overriding locational and business need is not met by cost savings from using land already owned (DL ¶20-21).
• Planting that takes time to mature and leaves winter and access views does not substantially lessen landscape harm (DL ¶13).

Policy findings

Policy codes are those of the National Planning Policy Framework (August 2026) unless a development plan is named.

Key facts

• Open countryside in the Carnmenellis landscape character area (CCA10), an open undulating plateau of small anciently enclosed fields (DL 11)
• Building of steel roof and timber cladding, separate from any farmstead, close to and visible from the highway and a public footpath (DL 12)
• Proposed orchard and hedge planting would not substantially lessen the harm, with views through the access and in winter (DL 13)
• Ecology reason for refusal overcome by an appraisal submitted at appeal; biodiversity gain documents also first submitted at appeal (DL 4-6)
• No evidence of contracts, projected income or that the location is operationally essential (DL 20-21)
• Absence of highway, noise or odour harm treated as neutral (DL 26)
• Parties had the opportunity to comment on the revised Framework (DL 3)

Sources

• Appeal on the Planning Inspectorate appeals service
• Decision letter (Planning Inspectorate)

This note is one of the decisions behind the NPPF 2026 Navigator, which shows how each Framework test has been applied across all the decisions in the database. Also available as Markdown.