Checking whether a development is built as approved

Start with the decision notice, not the building. Every full permission carries a condition listing the approved drawings by number and revision, and that list is the legal definition of what was allowed. Working out whether a development is not built as approved is a matter of comparing the structure in front of you against those specific drawings, then deciding whether the difference is something the council can act on.

Most of the work is reading, not measuring.

Obtaining the approved drawings

Search the council's online planning register by address. The application record holds the drawings, the officer report, the consultation responses and the decision notice, and in most authorities everything from roughly the last 15 years is scanned and public.

Older permissions are patchier. Where the drawings are not online, ask the council for them. Planning information is environmental information under the Environmental Information Regulations 2004, so a council should supply it on request, normally without charge for inspection, and you do not need to explain why you want it.

Download the drawings rather than viewing them in the browser. You need the scale bar, the drawing number and the revision letter legible, and browser viewers often crop the title block, which is where all three live.

Reading the decision notice and the plan references

Four things on the notice matter.

The description of development, which defines what was applied for. A description reading two storey rear extension does not authorise a three storey one, however the drawings were later amended.

The approved plans condition, usually the second or third condition, listing each drawing by number and revision. The revision letter is the part people skip. Drawing 102 Rev C and Drawing 102 Rev E can show quite different buildings, and only one of them is approved.

The other conditions, which carry obligations that are easy to check from outside: materials to be approved, obscure glazing to a named window, boundary treatment, landscaping, removal of permitted development rights, hours of construction.

The date, which starts the clock on the time limit for implementation, normally three years.

There is more on how the notice is structured in reading a decision notice as a neighbour, and it pays to read the whole thing before measuring anything.

Measuring what has been built

Measure from land you have a right to be on. A public footpath, the street, your own garden. Trespass undermines the complaint and can make the evidence unusable.

Useful references that need no equipment:

1. Brick courses. A standard brick course with its mortar joint runs at 75 millimetres, so counting courses from a damp proof course to an eaves line gives a height to within a few centimetres.
2. A standard external door at just over two metres, which calibrates a photograph taken square on.
3. Window and door openings on the approved elevation, which have dimensions you can scale and which appear in any photograph of the facade.
4. A fence or wall of known height in your own ownership, used as a scale in frame.

Photograph square on to each elevation, from a fixed position you can return to, with something of known size in the frame. Then overlay or compare against the approved elevation at the same scale. A difference of 150 millimetres in ridge height is hard to prove from a photograph. A whole extra storey, a roof form changed from hipped to gabled, a window where the approved drawing shows none, or a building 1.5 metres closer to the boundary: those show up clearly.

Note the things that are absent as well as the things that are different. Landscaping not planted, a bin store not built, an obscure glazed panel fitted as clear glass.

Minor deviations and material changes

There is no statutory definition of a minor deviation, and no tolerance written into the legislation. Every departure from the approved drawings is, strictly, development without permission.

In practice councils apply a judgement about materiality, and the authority usually treated as settled is that a permission for the construction of a building is a permission for the whole building, so a building must be completed in accordance with that permission to be lawful. On that reading, a developer who departs substantially from the approved drawings has not built the permitted development at all, rather than having built it with a small unauthorised addition.

What tends to be treated as material: changes to height, footprint, position relative to a boundary, roof form, the number of units, the position of windows facing a neighbour, and anything that would have changed the amenity assessment. What tends to be treated as immaterial: minor changes to internal layout, a different but visually similar brick, a rainwater pipe moved.

The honest answer to the question people most want answered is that the distinction is a judgement for the council, and two authorities can reach different views on the same facts.

Non-material amendments and how they appear

Before assuming a breach, check whether the change has been approved since the original permission. Three mechanisms, and they look different on the register.

A non-material amendment under section 96A of the Town and Country Planning Act 1990 requires no publicity and no consultation, so neighbours are not told. It appears as a separate application record, often with a suffix on the reference, and it issues an approval listing superseded and replacement drawings. These are the changes neighbours discover late.

A section 73 application to vary a condition, including the approved plans condition, is a planning application and is publicised. If a scheme was varied this way and you were not consulted, that is a separate question, covered in are neighbours reconsulted on amended plans.

A fresh application for a revised scheme runs in the normal way, and the original permission usually remains extant alongside it.

So search the register for every application at the address, not just the one you remember, and sort by date.

Raising a concern with the authority

Report it to the planning enforcement team, in writing, with five things: the address, the application reference, the drawing number and revision that shows what was approved, a plain description of what differs, and dated photographs.

Two expectations to set. Enforcement is discretionary: a council must decide whether action is expedient in the public interest, and it is not obliged to act on every breach, particularly where the harm is slight. And there are time limits after which a breach becomes immune from enforcement. The Levelling-up and Regeneration Act 2023 extended the immunity period for breaches in England, where previously a four-year period applied to building works and to change of use to a single dwelling with ten years for most other breaches. Which period applies depends on when the breach occurred, so ask the council to confirm rather than assuming.

A council that decides not to take formal action may still negotiate a revised scheme or invite a retrospective application. That is a normal outcome, not a failure, and it often produces the change you wanted faster than a notice would.

Keeping track of a case afterwards is its own exercise, set out in how to get an update on a planning enforcement case. Breaches of condition specifically have a dedicated and quicker route, described in breach of condition notices and what they achieve.

Evidence that helps an investigation

Enforcement officers work from evidence, and the complaints that progress are the ones that arrive with it.

• A dated log of what you observed and when, started as early as possible, including dates work began and stopped.
• Photographs from the same fixed position over time, which show sequence and are far more useful than a single image.
• The approved elevation annotated with what differs, which saves the officer an hour.
• Evidence of use where the breach is a change of use rather than building work: vehicle movements, signage, deliveries, opening hours, with dates and times.
• Where a section 106 obligation is involved, such as affordable units or a contribution, the agreement itself is public and checkable, as described in how to check what a section 106 agreement delivered.

Avoid two things. Do not photograph into private rooms, and do not fly a drone over the site, which has its own rules and will do more damage to your credibility than the images are worth.

This is general guidance, not legal advice; check the position with your local planning authority or a qualified professional before relying on it. A Lawful Development Certificate is the only formal way to confirm that works or a use are lawful.