Designations on the national planning data service

The national planning data service publishes designation datasets collected from local planning authorities in a consistent format, and it is now the fastest way to screen a site before you spend money on it. Conservation areas, article 4 directions, tree preservation orders, listed buildings, green belt, brownfield land registers and local plan boundaries are all there, in one place, downloadable and mapped.

It is also incomplete, and the gaps are not random. Understanding where the data comes from tells you which answers you can rely on and which need confirming with the council before you act.

What the service publishes and where it comes from

The datasets are assembled rather than created. Local planning authorities publish their own data, the service collects it, standardises the fields and republishes it under consistent names.

That is the source of both its usefulness and its limits. The geometry and attributes for a conservation area boundary originate with the authority that designated it, and the service reproduces what was supplied. Some datasets come from national bodies instead, which makes them more consistent: listed building entries derive from the national heritage list rather than from individual councils.

Each dataset carries an entry date and a source, and reading those fields is part of using the service properly. A conservation area boundary supplied three years ago does not reflect a designation made last month.

Coverage gaps by authority

Coverage varies by dataset and by authority, and the pattern is uneven. Some authorities have published article 4 direction boundaries in full. Others have published none. Tree preservation order coverage is patchy almost everywhere, because many orders predate digital mapping and have never been digitised.

That produces a specific and dangerous failure mode: a search returns nothing, and the reader concludes there is no designation. Absence of a record in a dataset with partial coverage is not evidence of absence on the ground.

The safe reading is asymmetric. A positive result is usually reliable, because the authority published it. A negative result tells you only that nothing has been published, and it has to be confirmed with the authority for any designation that would change your decision.

The datasets most useful for early screening

For an initial appraisal, a handful of layers do most of the work.

• Conservation area boundaries, which change the permitted development position and trigger demolition control.
• Article 4 directions, which remove permitted development rights and are the single most commonly missed constraint.
• Listed building entries, derived from the national list and reliable.
• Green belt boundaries, where published.
• Tree preservation orders, useful where present and never to be relied on where absent.
• Local plan boundaries and site allocations, which tell you what the plan intends for the land.
• Brownfield land registers, which indicate land the authority considers suitable for housing.

Two things the service does not replace. Flood risk comes from the Environment Agency's own published maps, and the natural environment designations sit on the government's magic mapping service. Use the right source for each rather than assuming one service covers everything.

What the service will not tell you

Three categories sit outside it entirely, and forgetting them is how an appraisal looks thorough and is not.

Private rights are absent. Restrictive covenants, rights of way in private ownership, ransom strips and easements appear in title documents rather than in planning data, and none of them are planning designations at all.

Consultation triggers are largely absent. Safeguarding directions for transport routes, consultation zones around hazardous installations and aerodrome safeguarding surfaces are held by the authority and by the relevant promoter or operator, and most are not published as an open dataset.

And the authority's own policy is only partly there. Site allocations and plan boundaries appear, but the text of the policy that applies to your site does not, and the supplementary planning documents that control design, parking standards and householder extensions are on the council's website rather than in the data.

Why the local register remains authoritative

The legally authoritative record of most designations is held by the local authority, and for many of them it is the local land charges register that a conveyancing search interrogates.

That matters in two situations. When you are relying on the absence of a constraint to make an offer, and when you are relying on the precise position of a boundary. Conservation area boundaries in particular are often drawn to follow historic property lines, and a site can be half in and half out with the line running through a building.

The practical rule is that the data service tells you what to investigate, and the authority tells you what is true. That sequence is the same one that applies to every other item worth checking a site for constraints before you make an offer.

Using the data for a site appraisal

The workflow that produces a defensible appraisal is straightforward.

1. Draw the site boundary accurately, because a sketched boundary produces false results at the edges.
2. Query the datasets relevant to the site type and the proposal, not every dataset available.
3. Record every result, including the nil results, with the dataset name and the date checked.
4. Buffer the search: designations near the site matter as much as designations on it, particularly listed buildings and their setting.
5. Take the positive results to the authority for confirmation and the significant nil results for verification.
6. Write the findings into the appraisal with the source and date against each item.

Step four is where most appraisals are thin. A listed building forty metres away does not appear in a query of the site outline, and its setting is still a material consideration.

Recording the date and source of a check

This sounds like housekeeping and is actually risk management. Data changes, designations are made and revoked, and an appraisal written eighteen months ago may be wrong now.

Record for each check the dataset name, the date you ran it, the boundary you used and the result. Keep a copy of the extract rather than a link, because published datasets are updated in place and the version you saw may not be retrievable later.

Where the appraisal supports a purchase or an option, that record is the evidence of what was known when the decision was made. Where it supports an application, it is what allows the Planning Statement to state the constraint position with a date attached rather than as an undated assertion.

Common misreadings

Four recur often enough to be worth naming.

Treating an empty result as a confirmed absence, which is the error discussed above and comfortably the most expensive.

Reading a boundary at the wrong zoom. Published geometry has a mapping tolerance, and a boundary that appears to run just outside your site at one scale can run through it at another. Where the answer turns on a few metres, ask the authority for the definitive plan.

Assuming currency. The dataset shows what was published, not what was decided last week. New article 4 directions and new conservation area designations are exactly the things that appear late.

And confusing adopted with emerging. A local plan boundary dataset may reflect an adopted plan, a submitted plan or something in between, and the weight attaching to each is entirely different.

Used with those cautions, the service is the most efficient screening tool available, and it has largely replaced the afternoon spent emailing four different departments to find out what a site is subject to. Use it to build the question list, then get the answers from the authority.

This is general guidance, not legal advice. Check the position with your local planning authority or a qualified professional before relying on it.

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