Tall buildings under policy D9: where and how assessed

Under London Plan policy D9, a tall building is acceptable in principle only where the site sits in a location that a development plan has identified as suitable for one. That is the gate, and it comes before any argument about architectural quality. The london plan tall buildings d9 assessment criteria then apply to the scheme itself, covering visual, functional, environmental and cumulative effects, each with an evidence base the borough and the Greater London Authority will test.

Applicants who lead with the design and treat the location question as arguable usually discover that it is not.

How boroughs define tall buildings locally

Policy D9 requires boroughs to define what counts as a tall building for particular localities in their development plans. The definition varies across London and within individual boroughs, reflecting prevailing context, but the policy sets a floor: the definition should not be less than six storeys or 18 metres, measured from ground to the floor level of the uppermost storey.

So a nine-storey building can be a tall building in one borough and unremarkable in another. Find the adopted definition for the specific locality before anything else, because it determines whether policy D9 is engaged at all and therefore what evidence the application needs.

Eighteen metres carries a second meaning. It is one of the height triggers for a higher-risk building under the Building Safety Act 2022 framework, so a scheme that crosses the tall building definition is often crossing the fire safety threshold at the same time.

Identifying appropriate locations in the development plan

Policy D9 part B asks boroughs to determine whether there are locations where tall buildings may be an appropriate form of development and to identify those locations on maps in their development plans. Tall buildings should be developed only in those identified locations.

That produces a straightforward first question for any site: is it inside a mapped tall building zone in the adopted local plan, an area action plan or an opportunity area planning framework. If it is not, the scheme is contrary to the development plan from the outset, and the case has to be made on material considerations strong enough to displace it under section 38(6) of the Planning and Compulsory Purchase Act 2004.

Some boroughs have adopted mapped locations. Others have definitions but no map, or a map inherited from a superseded plan. Where the plan is silent or out of date, the argument is available, but it is an argument about plan status rather than about design, and it needs to be made explicitly rather than assumed.

Visual impacts and the assessment expected

The visual criteria cover the effect on views, including the Mayor's designated strategic views and local views identified by the borough, the effect on the skyline both close up and at distance, the architectural quality of the building including its materials and detailing at street level, and the effect on heritage assets and their settings.

The evidence base is a Townscape and Visual Impact Assessment built on accurate visual representations. Viewpoints should be agreed with the borough and the Greater London Authority before the photography is commissioned, and the verified views need a documented methodology covering camera position, focal length, survey control and the rendering process. A set of attractive marketing images is not an assessment.

Where the scheme affects the setting of a designated heritage asset, the heritage assessment runs alongside rather than inside the townscape work, applying the statutory duties and national policy on harm and public benefits.

Functional, environmental and cumulative impacts

The functional criteria look inwards. Internal daylight and outlook for the homes being created, the arrangement of entrances, servicing and deliveries, the capacity of local infrastructure to take the additional demand, and fire safety, including the means of escape and the ability of the fire service to reach and use the building.

Fire is not a design afterthought at this scale. A Fire Statement is required for relevant buildings under Article 9A of the Development Management Procedure Order, and Planning Gateway One brings the Building Safety Regulator in as a statutory consultee. That document must be prepared by someone with the necessary fire engineering competence. It is not a report to draft and submit unreviewed.

The environmental criteria cover wind, daylight and sunlight to surrounding property and public space, light pollution from the building at night, air quality and microclimate, and interference with aviation, navigation and telecommunications where relevant.

Cumulative impact is the criterion people forget. The assessment has to consider the scheme alongside other consented and emerging tall buildings nearby, which means a cumulative townscape model, a cumulative wind case and a cumulative daylight case. On a site in an area with several live applications, agree the cumulative scenario with the borough early, because rerunning the models when the scenario changes is expensive.

Wind, daylight and microclimate evidence

Wind is assessed against pedestrian comfort and safety criteria, usually the Lawson criteria, and for anything of real height that means wind tunnel testing rather than computational modelling alone. The results drive canopies, podium form, screening and planting, which cost far less to design in than to bolt on. A Wind Microclimate Assessment should be commissioned at massing stage.

Daylight and sunlight to neighbouring property is assessed against the BRE guidance on site layout planning for daylight and sunlight, with the borough often setting expectations for how the targets are applied in a dense urban context. Sunlight to surrounding amenity space and public spaces matters as much as daylight to windows on a tall building scheme, and the overshadowing analysis should cover the equinox and the two solstices. Commission the Daylight and Sunlight Assessment early enough to influence the massing.

Public access and the top of the building

Policy D9 asks that free to enter publicly accessible areas be incorporated where appropriate, typically at the upper levels, with the aspiration that the public benefit of a tall building includes access to the view it takes.

Treat this as a real requirement rather than a gesture. A viewing level that is only reachable through a private lobby, only open by booking, or closed at the operator's discretion will be tested at committee. If public access is offered, the section 106 agreement needs to secure the hours, the route, the management arrangements and the absence of a charge.

Assembling a proportionate evidence base

Sequence beats volume. Establish the location position, then run the early massing against wind, daylight and cumulative townscape before the design is fixed, then build the full assessment around the resolved scheme.

Schemes over the referral thresholds go to the Mayor, which adds a stage and a set of expectations that the borough cannot waive. Build that into the programme. And expect the evidence base for a tall building to be an order of magnitude larger than for a mid-rise scheme on the same site, which is a cost that belongs in the appraisal at acquisition rather than at planning.

Browse the 66 PlanScope report types to scope the evidence base, and get the specialist reports reviewed by qualified professionals before submission.

This is general guidance, not legal advice. Fire safety documents require professional input with the necessary fire engineering competence, and for other specialist technical reports qualified professional input may be required. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.