Tall buildings: the plan location test before design

London Plan policy D9 asks one question before it asks anything about design: is the site in a location the development plan identifies as suitable for tall buildings. Part B of the policy states that tall buildings should only be developed in locations identified as suitable in development plans. The visual, functional, environmental and cumulative tests in Part C follow that, and they do not cure a failure on location. An architect who reaches stage 3 with a tower on an unidentified site has designed a departure application.

So the first drawing on a tall building project is not a drawing at all. It is a map of the borough's identified locations with the site plotted on it.

Why location comes before design quality

The sequence is deliberate. Policy D9 treats tall buildings as a form of development whose suitability is a plan-making judgement about townscape, infrastructure and character, made at borough level through a tall buildings strategy or a character study, rather than a question to be settled application by application.

That has a consequence worth stating plainly to clients. A beautifully resolved tower on a site the plan does not identify is in conflict with the development plan, and section 38(6) of the Planning and Compulsory Purchase Act 2004 requires the determination to be made in accordance with the plan unless material considerations indicate otherwise. Design quality is a material consideration. It is not a substitute for plan compliance.

Boroughs vary in how far they have taken this. Some have mapped specific sites and areas with maximum heights. Some identify broad areas without heights. A few have done little, which changes the argument but does not remove the policy.

How boroughs define a tall building

The definition is local, and it matters because it determines whether policy D9 applies at all. Policy D9 asks boroughs to define what constitutes a tall building for specific localities, and provides a default where they have not: buildings of six storeys or 18 m measured from ground to the floor level of the uppermost storey.

Check three documents in order:

• The adopted local plan policy on tall buildings and its definition for the area in question
• Any tall buildings strategy, character study or supplementary planning document
• Any site allocation covering the land, which may set its own height parameter

Read the default measurement carefully. Measuring to the floor level of the uppermost storey rather than to the roof or the parapet changes where a scheme sits relative to the threshold, and a plant enclosure above that level is treated differently from an additional occupied storey.

Note the overlap with the Building Safety Act 2022 regime, which uses 18 m or seven storeys to define higher-risk buildings. The numbers are similar and the purposes are different, so do not use one to answer the other.

Locations identified in the development plan

An identified location is one the plan says is suitable, which usually means it appears on a policies map, in a tall buildings strategy adopted as part of the plan, or in an allocation with a height parameter.

What does not count is a location where tall buildings already exist. Nor does an area the borough has described as having capacity for intensification without identifying it for tall buildings specifically. Nor does an opportunity area designation by itself, although it is a material consideration and our note on what a London allocation changes sets out how those designations work in practice.

Where a plan identifies a location but not a height, the design-led approach to capacity applies instead, and optimising site capacity under London Plan policy D3 is the relevant discipline.

Proposals outside an identified location

They do get consented, and the route is a reasoned departure rather than an argument that D9 does not apply.

1. Establish precisely what the plan says and how old it is, because a plan that predates the current London Plan may be out of date on this specific point
2. Identify whether the borough has in fact identified locations at all, since the policy bites differently where no exercise has been carried out
3. Build the case on the development plan as a whole, including housing delivery, allocation status and any area-based regeneration policy
4. Address every Part C test fully, because a departure with weak environmental evidence fails twice
5. Engage the Greater London Authority early, since most tall building applications are referable to the Mayor under the Town and Country Planning (Mayor of London) Order 2008 and the Mayor's view will shape the borough's handling

The referral thresholds include height-based categories, so check the current Order against the proposal rather than assuming a scheme is below them.

Visual, functional and environmental tests

Part C is where the technical evidence base lives, and the three headings each generate documents.

The townscape and visual impact assessment needs its viewpoints agreed with the borough and the Greater London Authority before the verified views are produced, because reshooting a view set late is expensive and delays the submission.

Wind is the test most often left until the design is fixed. A wind microclimate assessment that finds a problem at the base of a tower leads to podium changes, canopies and planting that alter the ground floor plan, so commission the desk study at concept stage rather than the wind tunnel test at the end.

Fire safety now sits inside the planning conversation. A fire statement for a relevant building must be prepared by someone with the necessary fire engineering competence, and the planning gateway process means the fire strategy influences core layout, stair provision and evacuation design from the first plan.

Cumulative effect of nearby consents

Cumulative impact means the effect of the proposal together with other tall buildings that are built, consented or allocated. It is assessed on the same three headings, and it is the test that most often produces a refusal for the second or third tower in a cluster.

Assemble the commitments list early and keep it current. Include schemes consented but unbuilt, schemes at appeal and allocations with height parameters, and state the date the list was compiled. A verified view showing only the proposal in an otherwise unchanged skyline invites the officer to produce the cumulative version themselves.

Microclimate effects accumulate too. Wind acceleration between towers, overshadowing of a shared public space and the combined effect on a protected vista are all cumulative questions that a single-site assessment misses.

Evidence that supports a departure

Where the case is a departure, the evidence has to be stronger than for an identified site rather than the same.

Expect to need the full Part C suite, a design and access statement that explains the height as a response to context rather than to viability, a housing delivery argument grounded in the borough's position, and an honest cumulative assessment. Add early pre-application engagement with both the borough and the Greater London Authority, minuted.

One honest caveat: a scheme that fails the location test and relies on design quality alone has a poor record, and a client is better served by hearing that at the feasibility stage than after a year of design fees. If the location is not identified, the plan position is the project risk.

Browse the report types to see which of the Part C documents a tall building proposal is likely to need before you commit to a massing.

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. For specialist technical reports, qualified professional input may be required, and a fire statement legally requires an author with the necessary competence.