Daylight baselines where a consented neighbour is unbuilt

Where a neighbouring site holds a planning permission that has not been built, a daylight assessment should report both baselines: the existing situation on the ground and the situation as it would be with the consented scheme in place. Choosing one and omitting the other is the single most common reason these assessments get challenged, because the choice usually flatters whoever made it.

The existing situation is the primary baseline, because it is the amenity people currently enjoy. The consented scheme is a material consideration whose weight depends on how likely it is to be built. Both belong in the report, labelled, with the difference explained.

Why the baseline choice changes the answer

Take a site with a two-storey workshop next door and a permission for a six-storey block on the same plot. Your scheme is assessed for its effect on windows across the street.

Against the existing situation, those windows currently see a lot of sky over the workshop roof, so your proposal produces a large percentage reduction in vertical sky component and a clear breach of the benchmark. Against the consented scheme, the windows already lose most of that sky to the approved six storeys, so your additional effect is marginal and the percentages look comfortable.

Same building, same windows, two completely different conclusions. And the reductions are not additive in a simple way, because a window that has already dropped below the benchmark in the baseline cannot drop below it again, so the relative test behaves differently in each scenario.

That is why objectors go straight to the baseline. If the assessment reports only the consented scenario, the obvious criticism is that the applicant has taken credit for harm that has not happened yet and may never happen.

The existing situation as the primary baseline

Start here and present it first.

The reason is practical rather than doctrinal. Planning protects the living conditions of real people in real buildings, and the occupier of a flat opposite does not experience a consented scheme as a loss already suffered. If the consent lapses, the existing situation is the only situation there will ever have been.

The BRE guidance supports that reading. Its benchmarks are expressed as changes relative to the existing condition at the affected window, and the standard approach is to measure from what is there. The 2022 revision is more explicit than its predecessor about also considering committed development, and about the cumulative picture where several schemes are in play, but it does not displace the existing situation as the starting point.

So the structure that works is: existing situation results in full, consented scheme results in full, then a short comparison explaining the difference and what the applicant says follows from it.

Assessing against a consented but unbuilt scheme

The consented scenario is worth doing properly rather than as a footnote, because in many urban situations it is the realistic future and the officer knows it.

Model the consent as approved, not as the applicant hopes to amend it. That means the approved drawings, the approved heights and the approved massing, including any element the developer next door has been grumbling about. Where the consent has been varied under section 73, model the current operative permission and say which decision you used.

State the consent's details so a reader can check them: the application reference, the decision date, the date by which development must begin, whether development has lawfully begun, and whether pre-commencement conditions have been discharged. Those five facts are what the weight argument turns on, and they are all on the council's public register.

Where more than one neighbouring consent exists, model the cumulative scenario as well. Three unbuilt consents around a courtyard produce a future condition that no single one of them describes.

How much weight an extant consent carries

This is a planning judgement rather than a technical one, and the factors are reasonably settled.

A permission that has been lawfully implemented is in a different category altogether. Once development has begun in accordance with the permission, the permission does not lapse, so the consented scheme becomes close to a certainty and the argument for using it as the realistic baseline is strong.

A permission with nine months left, nothing discharged and the site advertised for sale deserves little weight, and an assessment resting on it will be treated accordingly.

Protecting the windows of a scheme not yet built

The question also runs the other way, and it is less often handled well. Does your scheme have to protect the daylight of windows in a neighbouring building that has been consented but not built?

In practice councils do give weight to the amenity of a consented scheme's future occupiers, particularly where the consent is recent, implementation looks likely and the two sites are in a plan-led area where both allocations were intended to come forward. Ignoring those windows entirely invites an objection from the neighbouring developer, who will notice at once.

The pragmatic approach is to assess them as a separate scenario, clearly labelled, and to be clear about the asymmetry: a consented scheme cannot claim the protection of an existing occupier, because nobody lives there, and it can reasonably ask that its approved windows not be rendered unusable by a later application.

Where both sites are allocated and expected to be developed together, the better answer is to design against the neighbouring consent from the outset, which takes less effort than arguing about it. The daylight performance of the proposed units themselves, assessed in the same model, is the subject of internal daylight assessment for proposed dwellings.

How inspectors have approached it

Appeal decisions are indicative of how inspectors handle the question rather than binding precedent, and the pattern that emerges is consistent.

Inspectors generally take the existing situation as the primary comparator, because that is the condition occupiers experience. They do take account of a consented scheme where the evidence shows implementation is likely, and they give it less weight where it is speculative. They are notably unimpressed by assessments that present only the flattering scenario, and that criticism tends to colour the rest of the evidence. And where both scenarios are presented honestly, the decision usually turns on the planning balance rather than on a dispute about method.

One honest uncertainty. There is no national guidance that resolves how to weigh an unbuilt consent in a daylight assessment, and different authorities and different inspectors have reached different conclusions on similar facts. Anybody who tells you the answer is settled is overstating it.

Wording the assessment

Name the scenarios plainly and use the same names throughout the report, the drawings and the summary tables. Something like existing situation, consented scheme scenario and cumulative scenario, with no abbreviations that a committee member has to decode.

Then in the methodology section, set out the consent details listed above, state which scenario you treat as primary and why, and say explicitly that the results are reported for both rather than averaged or combined. In the results, keep the two sets of figures on facing pages or in adjacent columns, never in separate appendices.

In the conclusion, answer the question an officer actually has to decide. Not which baseline is correct, but whether the effect on living conditions is acceptable, and how that answer changes between the scenarios. Where it is acceptable under both, say so in one sentence and the issue disappears. Where it is acceptable only against the consented scheme, say that too, because the officer will work it out and would rather read it than find it.

The daylight and sunlight assessment is the place for all of this, and the summary should be readable without the appendices. Amenity space and garden sunlight follow the same baseline logic and belong in an overshadowing study using the same labelled scenarios. Where a neighbour objects on the basis of the figures, the approach to answering is set out in answering a neighbour's daylight objection.

This is general guidance, not legal advice. Daylight and sunlight assessment should be carried out by a suitably qualified consultant, and councils usually expect a named author for this work.

To see which daylight and amenity documents a scheme is likely to need, enter your postcode on PlanScope and work through the guided questions. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.