NPPF S5 helps self-build home win Horsham countryside appeal

A self-build home outside a defined settlement boundary has been allowed on appeal after the Inspector applied the new NPPF S5 provision for limited infilling within a group of houses.

The proposal conflicted with Horsham’s development-plan spatial strategy. However, the August 2026 national policy changed the planning balance.

The appeal, 6009593, concerns land east of Spring Gardens, Washington, RH20 3BP. Inspector Jane Smith issued the decision on 10th September 2026.

A countryside site between existing homes

The application, DC/26/0035, proposed a two-storey detached self-build dwelling, landscaping and relocation of an existing stable.

The site lay outside the defined built-up area. The Inspector found conflict with the spatial strategy in Policies 2, 4 and 26 of the Horsham District Planning Framework.

But this was not a proposal to place an entirely isolated house in an open field. The plot lay between 1 Spring Gardens and The Orchard, fronting the same road and forming part of a cohesive group of houses.

That relationship became important when the Inspector assessed the policy introduced in the NPPF published on 17th August 2026. Both main parties were given an opportunity to comment on the new Framework.

What NPPF S5 changed

Policy S5 identifies forms of development which can be supported outside settlements. Its limited-infill route is at S5(1)(e): “Limited infilling within groups of houses”.

The Inspector found that the proposed home would sit naturally within the existing group. It would occupy a gap between dwellings, front the same road and have a broadly comparable relationship to neighbouring plots.

On those facts, the scheme qualified as limited infilling. National policy therefore provided an important material consideration despite the development-plan conflict.

Our guidance on the presumption in favour of sustainable development explains how national policy is considered alongside the development plan. The new policy does not mean settlement boundaries have disappeared.

Do not merge the separate S5 routes

The most useful point in the decision is how the Inspector kept the policy’s different routes separate.

S5(1)(j) addresses evidenced unmet need and includes a requirement for the relevant development to be physically well-related to an existing settlement. The Inspector did not find that route satisfied here: the nearest defined settlements were too distant.

However, that did not dispose of the separate limited-infill route in S5(1)(e). The Inspector found no basis for importing the settlement-relationship requirement from another limb into the limited-infill provision.

A group of houses can therefore be relevant to S5(1)(e) without itself qualifying as a settlement for S5(1)(j). The distinction is particularly useful when considering building outside a settlement boundary.

This is not a reason to ignore the rest of S5 or other applicable policies. It is a reason to identify the actual route relied upon and apply its wording, rather than combining several different tests into one.

The stable did not make the whole plot brownfield

The site included an existing stable and hardstanding. The Inspector accepted that part of it could be treated as previously developed land.

But the proposed house also extended onto paddock land. The previously-developed-land route was therefore not a complete answer to the scheme as a whole.

The appeal succeeded through the limited-infill assessment, rather than by treating every part of the land as brownfield simply because a stable stood nearby.

The planning balance still mattered

Qualifying as infill was not the end of the assessment. The Inspector considered the proposal’s effect on the character of the area, access to services and the benefits of providing a home.

There were some facilities within walking distance and bus services nearby, but future residents would still depend on a car for many day-to-day needs. The Inspector gave that harm moderate weight rather than overlooking it.

The housing contribution was modest because only one home was proposed. Nevertheless, the decision gave weight to meeting housing needs, self-build provision and support for the vitality of the locality.

The Inspector concluded that the benefits were not substantially outweighed by the adverse effects under S5. The new national policy justified approval notwithstanding conflict with the development plan taken as a whole.

This was therefore not an isolated-home permission based on an exceptional design or rural-worker need. The relationship to the existing group of homes was fundamental.

A self-build label did not settle the BNG question

The appeal also raised a separate issue about the statutory self-build exemption from biodiversity net gain.

An initial unilateral undertaking, dated 31st July 2026, did not adequately deal with what would happen if the development ultimately failed to qualify for the exemption. In particular, a first occupier without the required input into the design could fall outside the relevant self-build definition.

A later bilateral Section 106 agreement dated 2nd September 2026 provided a mechanism requiring BNG if the exemption did not apply, together with associated monitoring and dispute-resolution arrangements.

The Inspector accepted that agreement as addressing the concern. This description follows the decision’s assessment of the agreement; it should not be mistaken for a quotation from the executed deed.

The practical lesson is simple: where an exemption depends on what is actually delivered, an application’s description is not enough. The permission and obligation need to deal properly with the relevant circumstances.

An important date qualification for new applications

This appeal must not be read as confirmation that every new self-build proposal still benefits from the former self-build BNG exemption.

Current government guidance states that the specific exemption no longer applies to new applications made on or after 6th August 2026, subject to the relevant transitional arrangements for earlier applications.

The appeal concerned an application already in the system before that change. Regulation 4(2) of the 2026 amending Regulations preserves the older exemption for applications made before 6th August 2026. The decision needs to be understood in that context.

A new self-build proposal may still qualify under a different exemption. For example, the new exemption for sites no larger than 0.2 hectares requires that the development does not impact an onsite priority habitat, and has its own application-date restrictions. Losing the specific self-build exemption does not mean every self-build project must provide mandatory BNG.

Our self-build planning guide and the government’s current guidance on BNG exemptions should be checked before assuming that the same position applies to another proposal.

Planning Geek analysis: start with the right policy limb

A plot outside a settlement boundary can raise several different policy questions. This decision shows why they should be considered separately.

It matters whether the proposal is redevelopment of previously developed land, limited infilling within a group of houses, or development addressing an unmet need under another limb. Failure under one route does not necessarily answer the others.

For potential infill sites, the relationship to existing houses should be demonstrated clearly: the extent of the group, the road frontage, the gap being filled and the arrangement of neighbouring plots. Calling a scheme infill does not establish those facts.

Read the appeal decision

Download the Spring Gardens appeal decision and conditions: 6009593. The application is DC/26/0035, and the decision date is 10th September 2026.

This article reports the Inspector’s findings and distinguishes them from Planning Geek’s practical analysis. It does not establish that all gaps between countryside houses should be approved.

Report prepared: 11th September 2026