Full planning permission vs prior approval: what's the difference?

What is full planning permission?

Full planning permission is the standard route for obtaining consent to carry out development. You submit a formal application to your local planning authority (your London borough council), which assesses the proposal against the borough's Local Plan policies, the London Plan, and the National Planning Policy Framework (NPPF). The council has broad discretion to approve, approve with conditions, or refuse your application.

A householder planning application -- the type used for extensions, loft conversions, and other alterations to a single dwelling -- costs £258 in council fees (2026 rate). The statutory determination period is 8 weeks, though many London boroughs regularly take longer.

The key feature of full planning is that the council assesses your proposal holistically. They consider design quality, impact on neighbours (daylight, privacy, outlook), the character of the streetscape, parking and transport, trees, ecology, flood risk, and any other material planning considerations. Neighbours are formally notified and given 21 days to comment. The case officer weighs all of these factors in reaching a recommendation.

Full planning permission, once granted, is valid for three years. You can start work at any point within that period. If you do not start within three years, the permission lapses and you must reapply.

What is prior approval?

Prior approval is a different animal entirely. It is a lighter-touch process that applies to specific types of development that are already permitted in principle by the General Permitted Development Order (GPDO). The development itself does not need planning permission -- it has automatic PD rights. But the GPDO requires you to notify the council and give them the opportunity to assess the proposal against a limited set of criteria before you start.

The critical distinction is scope. In a prior approval process, the council cannot assess your proposal against general planning policies. They can only consider the specific criteria listed in the relevant class of the GPDO. If your proposal meets those criteria, the council must approve it -- they have no discretion to refuse on design, character, or policy grounds.

If the council fails to respond within the statutory determination period, prior approval is deemed to be granted. This automatic approval mechanism does not exist for full planning applications, where failure to determine within time simply gives you the right to appeal for non-determination.

The Larger Home Extension scheme (Class A, Part 1)

The most common prior approval route for London homeowners is the Larger Home Extension scheme, introduced in 2013 and made permanent in 2019. It allows single-storey rear extensions up to 6 metres from the original rear wall (8 metres for detached houses) to be built under Permitted Development, subject to prior approval from the council.

The only assessment criterion is the impact of the extension on the amenity of any adjoining premises. The council notifies neighbours, considers any objections relating to amenity impact, and makes a decision within 42 days. They cannot consider design, materials, overlooking from upper-floor windows, or policy compliance -- only whether the extension would unacceptably harm the amenity of adjoining occupiers.

Commercial-to-residential conversions (Class MA)

Class MA of the GPDO permits the change of use from commercial, business, and service uses (Use Class E) to residential (Use Class C3). This covers offices, shops, restaurants, and light industrial premises being converted to homes. The prior approval criteria are more extensive than for the Larger Home Extension scheme and include transport, contamination, flooding, noise, natural light, fire safety, provision of adequate bin storage, and the impact on the character and sustainability of the local area.

The fee is £120 per dwellinghouse being created, and the determination period is 56 days. Article 4 Directions can remove Class MA rights -- several central London boroughs have done this to protect commercial space in prime locations.

Side-by-side comparison

Costs compared in detail

The fee difference between the two routes is modest but real. Here is what you pay in total for each route on a typical London project:

The drawing requirements are similar for both routes. You still need accurate existing and proposed floor plans, elevations, and a site/block plan. For full planning, you may also need a Design and Access Statement (included in our Complete package). For prior approval, the drawings can be simpler -- but they must still clearly show the dimensions and relationship to boundaries and neighbouring properties.

Timelines compared

Prior approval is faster on paper and often faster in practice:

The 42-day prior approval period is a hard deadline. If the council does not issue a decision by day 42, the prior approval is deemed granted. This creates a powerful incentive for councils to respond promptly. In practice, most London boroughs issue prior approval decisions within 30–35 days.

Full planning has no equivalent automatic approval mechanism. If the council does not decide within 8 weeks, you can appeal to the Planning Inspectorate for non-determination, but this adds months to the process. Many London boroughs ask applicants to agree extensions of time, which can push householder decisions to 10–12 weeks.

Neighbour consultation

Both routes involve neighbour notification, but the scope of what neighbours can usefully object to differs significantly.

Full planning

Neighbours can object on any material planning ground: loss of light, loss of privacy, overbearing impact, design quality, noise, traffic, character of the area, and anything else they consider relevant. The case officer must consider these objections in their assessment, though they are not bound to agree with them.

Prior approval

Neighbours are notified and can submit comments, but the council can only consider objections that relate to the specified criteria. For the Larger Home Extension scheme, this means only the impact on amenity of adjoining premises. Objections about design, property values, loss of views, or character of the area are irrelevant and cannot be used as grounds for refusal.

This is a significant advantage of the prior approval route if you anticipate neighbour resistance. A neighbour who would strongly object to your extension on design grounds has no effective mechanism to block a prior approval application -- provided your extension meets the dimensional criteria and does not demonstrably harm their amenity.

Which projects qualify for each route?

Prior approval is available for:

• Single-storey rear extensions between 4m and 6m (terraced/semi) or 4m and 8m (detached) from the original rear wall -- the Larger Home Extension scheme
• Commercial-to-residential conversions under Class MA (Use Class E to C3)
• Agricultural-to-residential conversions under Class Q
• Demolition and rebuilding of certain buildings under Class ZA
• Upward extensions to create new homes on certain buildings under Classes AA and AD

Full planning is required for:

• Any extension exceeding PD limits that does not qualify for prior approval
• Two-storey extensions (no prior approval route)
• Side extensions (no prior approval route for larger side extensions)
• Mansard roof extensions -- always need planning permission
• Extensions to flats -- no PD rights, no prior approval
• New dwellings (garden infill, new build)
• Change of use not covered by a GPDO class
• Work in conservation areas where PD rights are restricted
• Work subject to Article 4 Directions removing the relevant PD class

When to choose full planning even if prior approval is available

There are several scenarios where applying for full planning permission is the better strategy, even when prior approval is technically available:

• Complex or unusual design. If your extension involves non-standard materials, unusual geometry, or a design you want formally approved and documented, full planning gives you a decision notice that endorses the specific design shown on your drawings. Prior approval does not assess design.
• You plan to sell before building. A full planning permission on the property title is a more recognisable and reassuring asset to buyers and their solicitors than a prior approval notice. Some buyers may not understand what prior approval is.
• The Larger Home Extension completion requirement. Under the Larger Home Extension scheme, the extension must be completed within 3 years. With full planning, you only need to start within 3 years -- you can then take as long as you need to finish. This gives more flexibility on phasing.
• Future flexibility. If you might want to modify the design during construction, a full planning permission with conditions is easier to vary (via a Section 73 application) than a prior approval.
• Pre-application advice suggests full planning. If your borough's planning team has recommended full planning during a pre-app consultation, follow their advice. They may have identified issues that make prior approval risky.

Appeal routes

Both full planning refusals and prior approval refusals can be appealed to the Planning Inspectorate. However, the appeal for a prior approval refusal is limited to the same criteria that the council was allowed to consider. The inspector cannot introduce new grounds.

For the Larger Home Extension scheme, if the council refuses prior approval on amenity grounds, the inspector will assess whether the extension genuinely harms the amenity of adjoining premises. If the council's decision was unreasonable, the inspector will overturn it and grant prior approval.

Full planning appeals are broader in scope. The inspector conducts a fresh assessment of the entire proposal against all relevant planning policies. This can work in your favour (the inspector may take a different view of the merits) or against you (the inspector may identify issues the council missed).

Householder appeals are typically decided within 8–12 weeks. Prior approval appeals tend to be slightly faster because the scope of assessment is narrower.

Our drawing service covers both routes

At Architectural Drawings London, we prepare drawings for both full planning applications and prior approval applications. The quality standard is the same -- accurate, scaled, professionally presented drawings that give the council everything they need to make a decision. Our fees start from £840 for either route.

We also advise on which route is best for your specific project. In many cases, the choice is clear-cut. In others -- particularly for rear extensions between 4m and 6m on terraced or semi-detached houses -- both routes are viable and the right choice depends on your specific circumstances, your neighbours, and your borough's planning policies.

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