Breaching one condition and losing the whole right

Permitted development is an all or nothing permission. Article 3(1) of the General Permitted Development Order 2015 grants planning permission for the classes of development in Schedule 2 subject to any relevant exception, limitation or condition specified there, and if a condition is not met, the permission does not apply. The extension is then unauthorised development, not a permitted development with a minor defect, and that is a far worse position than most householders realise when they ask the builder to use a different brick.

The practical version: build a rear extension to 4 metres on a sloping plot and exceed the height by 100 millimetres, and the whole extension needs planning permission. Fit a clear-glazed opening window at first floor in the side elevation of a loft conversion, and the whole loft conversion needs planning permission. There is no partial lawfulness and no officer discretion to overlook it.

Why conditions are not advisory

The Order reads as a grant of permission with strings attached, and the strings are part of the grant rather than guidance alongside it. A condition in Schedule 2 operates as a qualification on the permission: satisfy it and you have permission, fail it and you never had permission for that development at all.

That is different from a condition on a planning permission issued by a council. Breaching a condition on a decision notice is a breach of condition, enforceable by a breach of condition notice, and the underlying permission survives. Breaching a condition in the Order means the development was never permitted, so what you have is development without planning permission.

The consequence shows up in the enforcement route the authority chooses, and in what you have to do to fix it.

Limitations against conditions in the Order

Each class in Schedule 2 has the same three-part structure, and the distinction between the parts matters less than people think, because the outcome is the same.

Exceed a limitation and the works are simply not within the class. Breach a condition and the permission granted by the Order does not apply. Either way you are looking at unauthorised development, and the practical difference is only in how the officer writes the report.

The curtilage coverage test is the limitation that catches most householders, and it has its own body of practice set out in the note on the 50 per cent curtilage rule for garden outbuildings.

What happens the moment a limit is exceeded

The breach crystallises when the works are carried out, not when the authority finds out. From that point:

• The development is a breach of planning control under section 171A of the Town and Country Planning Act 1990
• The authority may serve an enforcement notice requiring removal or alteration
• The works are unlawful for the purposes of a sale, and a buyer's solicitor will raise it
• Indemnity insurance may be available for an old, unchallenged breach, but it is not available once the authority has been notified
• A lender may decline to lend, or require regularisation before completion

Nobody rebuilds a whole extension over 100 millimetres in practice. What usually happens is an application that regularises the development, or an alteration that brings it within the class, or a long wait for the time limits to run.

Materials conditions and the similar appearance test

The materials condition in Class A requires the materials used in any exterior work to be of a similar appearance to those used in the construction of the exterior of the existing house. Similar, not identical, and appearance rather than specification.

In practice officers look at colour, texture and module. A modern wirecut brick next to a handmade stock reads differently even at the same colour, and a profiled concrete tile beside a clay plain tile does not match. Render over blockwork beside a brick house usually fails, which is the most common materials breach on rear extensions.

The condition does not apply to a conservatory or to certain rear extension situations in the same way, so read the condition in the class you are using rather than assuming. Where materials are marginal, the safe route is to agree them with the council in writing before ordering, or to apply for planning permission so the materials are approved by condition.

Front garden surfacing has its own class and its own condition about permeability, covered in the note on front garden paving, permeable surfaces and Class F.

Correcting a breach after the build

Four routes, in rough order of cost.

1. Alter the works to comply. Replacing a clear window with obscure glazing that is non-opening below 1.7 metres, or cutting a roof down by 150 millimetres, can bring the development back inside the class. Take advice first, because the question of whether retrospective compliance cures the original breach is not straightforward.
2. Apply for planning permission retrospectively under section 73A. The application is judged on its planning merits, and a well-built extension that misses a permitted development limit by a small margin is usually acceptable.
3. Apply for a lawful development certificate for existing development under section 191, where the works may be immune because of the passage of time.
4. Remove the works.

Route two is the normal answer, and the application should be framed around the harm rather than the breach. A Planning Statement that compares the extension as built against what would have been permitted, and shows the difference in impact, gives the officer a reason to approve rather than a reason to enforce.

Illustrative example. A single storey rear extension built to 4.2 metres where 4 metres was permitted, on a plot falling 400 millimetres away from the house. The owner applied retrospectively. The officer report noted that the additional height was not visible from the street, that the neighbouring windows were unaffected on a 45 degree test, and recommended approval. The cost was an application fee and a set of as-built drawings. Figures are illustrative.

Enforcement exposure and the time limits

Immunity depends on time, and the time limits changed. For breaches in England occurring on or after 25 April 2024, the Levelling-up and Regeneration Act 2023 extended the period for taking enforcement action against operational development and most changes of use to ten years. Breaches before that date remain subject to the previous four year period for operational development and change of use to a single dwellinghouse, with ten years for other uses and for breaches of condition.

Two practical points. A breach discovered in year three now has seven more years of exposure rather than one, which changes the calculation for anyone hoping to wait it out. And an authority can serve a planning contravention notice at any time to establish the facts, which starts a paper trail that makes later indemnity cover unavailable.

Concealed breaches have their own rule, and a planning enforcement order can be sought where development was deliberately concealed, which effectively removes the time limit.

Using a certificate to confirm the position

Where the works do fall within the class and the dispute is about measurement, a lawful development certificate settles it. For proposed works it is a section 192 application, and for completed works a section 191 application, and the certificate binds the authority.

The application needs evidence rather than assertion: a measured survey with levels tied to a datum, the original dwellinghouse established from historic mapping or council records, a schedule of previous enlargements, and the arithmetic against each limit. Supply all of it, because the burden of proof is on the applicant and an officer who cannot verify the figures will refuse.

And apply before building where anything is marginal. A section 192 certificate costs a fraction of what a retrospective application and a rebuilt roof cost together.

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 are lawful. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.