Tall buildings and policy D9: location, design, impact

London Plan policy D9 on tall buildings has three limbs and applicants lose on the first one more often than on the other two combined. The policy asks boroughs to define what counts as a tall building in their area, to identify locations where tall buildings may be appropriate in their development plans, and then to assess proposals in those locations against a long list of design and impact criteria. A tall building outside an identified location starts from a position of policy conflict, whatever its architectural quality.

So the first question on any site is not how tall can we go. It is whether the borough's plan says tall buildings belong here at all.

How a tall building is defined

There is no London-wide height threshold. Policy D9 requires boroughs to determine what constitutes a tall building for different parts of their area, with the definition expressed in the development plan, and it sets a floor by stating that the definition should not be less than six storeys or 18 metres measured from ground to the floor level of the uppermost storey.

That floor matters for two reasons beyond policy. Eighteen metres is also the threshold at which the higher-risk building regime under the Building Safety Act 2022 engages, and it is the trigger for the fire statement requirement under article 9A of the Development Management Procedure Order 2015 for relevant buildings.

So a scheme at the bottom of the tall buildings definition is simultaneously entering the Planning Gateway One process. Check the borough's own definition first, then check whether your building crosses 18 metres or seven storeys on the Building Safety Act test, because the two measurements are taken differently.

The location limb

Policy D9 part B is the gatekeeper. Tall buildings should only be permitted in locations identified as suitable in the development plan, and boroughs are expected to identify those locations through plan-making rather than through development management.

In practice that means looking for a tall buildings policy, a tall buildings strategy or an area action plan that identifies suitable locations, often in opportunity areas, town centres or around transport interchanges. Some boroughs have mapped locations precisely. Others have policy criteria without a map, and a few have neither, which leaves the development plan silent.

Where the plan is silent or the site is outside an identified location, you are arguing that the plan should be departed from. That is a legitimate argument, and it needs to be made on its terms: the age of the plan, the weight it carries, the characteristics of the site, the development plan taken as a whole and any material considerations that justify a different outcome. It is not won by asserting that the site is well connected.

Our note on opportunity areas covers what a strategic allocation does and does not deliver on this point.

The design limb

Part C of the policy runs through visual, functional, environmental and cumulative impacts. Treating it as a checklist to be answered in sequence is the method that works, because a borough officer will read it that way.

The visual criteria cover the building's contribution to the skyline, its relationship to the existing and emerging context, the effect on views including protected vistas and strategic views, the legibility of the building at street level, and the quality of the top, middle and base as a composition. Architectural quality is assessed as a whole rather than at the level of the facade treatment.

Functional criteria cover entrance arrangements, the ground floor's contribution to the street, servicing and refuse, how the building copes with crowds, internal daylight and outlook, and the provision of amenity space at height.

Environmental criteria are where the technical reports live. Wind microclimate at ground level, daylight and sunlight to surrounding properties and to open spaces, overshadowing of public space, solar glare from glazed facades, noise from plant at roof level, and aviation safeguarding where relevant.

A wind microclimate assessment and a daylight and sunlight assessment are the two that most often change a design, because wind mitigation needs podium form and canopies rather than landscaping, and daylight results drive setbacks at upper levels. In dense inner London the comparative targets in the guidance matter more than the absolute ones, which our note on BRE 209 in dense London takes further.

Cumulative effects and clusters

Part C also requires cumulative impacts to be considered, which means your building plus the consented and emerging schemes around it. On a cluster site this is the hardest piece of work, because the baseline keeps moving.

Agree the cumulative scenarios with the borough and the Greater London Authority before the studies run. The usual approach is a consented baseline and a scenario including applications under consideration, with the wind and daylight studies run on both. Running only the current baseline produces results that will be rejected.

But cluster logic also cuts the other way. In a location where the plan identifies a cluster, a building that steps down away from the cluster's peak reinforces the strategy, while a building of equal height at the edge flattens it. Officers read massing diagrams for that reading before they read the elevations.

The evidence a tall building application carries

Beyond the standard documents, expect to need an accurate visual representation study prepared to an agreed methodology with agreed viewpoints, a townscape and visual impact assessment, a microclimate study, a daylight and sunlight assessment covering neighbouring properties and amenity space, a fire statement, an energy strategy addressing the net zero carbon target, and a whole life carbon assessment.

Viewpoint agreement is the step applicants skip. Verified views have to be taken from locations the borough and the Greater London Authority accept, including protected vistas where they apply, and a study using self-selected viewpoints invites the objection that the worst views were avoided. Agree the list in writing and keep the correspondence.

The carbon position is not a side issue on a tall building. Form factor works against you, embodied carbon rises steeply with height and structure, and the residual carbon drives the offset payment secured under section 106. A whole life carbon assessment run alongside the energy strategy is the only way to see the two together, and on a tall building the structural frame choice dominates the result.

Where schemes fail

Four failure patterns recur.

The site is not in an identified location and the application does not acknowledge it. An officer report that opens with a conflict with part B of policy D9 is very hard to recover from.

The building is tall for the plot rather than tall for the place, so the ground floor is dominated by cores and servicing and the street frontage is dead. Policy D9's functional criteria exist precisely to catch this.

The wind study arrives late and the mitigation is bolted on. Canopies, screens and planters added after planning committee rarely satisfy the Lawson criteria and never look designed.

Cumulative assessment is missing or built on a stale baseline, which leaves a gap an objector can exploit.

One honest uncertainty: borough definitions and identified locations are being revised through local plan reviews, so the policy position on a given site can change between a pre-application meeting and a submission. Check the plan's status and any emerging policy, and ask the borough directly whether a tall buildings policy review is underway.

Enter your postcode on PlanScope to see which of the 66 reports your site is likely to need, including the fire statement required at Planning Gateway One. A fire statement must be prepared by someone with the necessary fire-engineering competence, which is legally required for relevant buildings, so an AI-assisted draft is a starting point for that professional rather than a substitute.

This is general guidance, not legal advice. Check the position with your local planning authority or a qualified professional before relying on it. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.