PD vs full planning: which route for your extension?

Last reviewed: 2026-07-01

The quick answer

Permitted Development (PD) lets many house extensions proceed without a full planning application, provided you stay within strict national limits on size, height, materials and position. Full planning is required when you exceed those limits, when PD rights are removed, or when you want a design PD cannot allow.

The right route depends on your property — not your preference. Flats, listed buildings and many conservation-area sites cannot use standard PD. Even on a normal semi, a deep rear extension or side wrap may need prior approval or full planning. Use the PD Quick Check for a first steer, then confirm with drawings and (where appropriate) a Lawful Development Certificate.

Official reference: GOV.UK permitted development rights for householders.

When is Permitted Development enough?

PD works well when:

• The property is a house (not a flat or maisonette).
• PD rights have not been removed by condition or Article 4 direction.
• Your scheme fits volume, height and projection limits measured from the original house.
• Materials are similar in appearance where required.
• You are not proposing banned features (balconies, verandas, raised platforms facing the highway, etc.).

Single-storey rear extensions within depth limits, modest side infills, many loft conversions (with volume caps), and some outbuildings commonly qualify. Our PD hub explains the detail in plain English.

PD does not replace building regulations. You still need structural design and building control approval regardless of planning route.

When should you choose full planning?

Full planning is the safer or only option when:

• You want a two-storey side extension or form outside PD envelopes.
• The property is listed or in a conservation area with restricted rights.
• You need non-compliant materials or elevational changes PD forbids.
• Previous permissions removed PD rights (common on new estates).
• Neighbour overlooking or amenity issues need a negotiated design — planning can condition solutions PD cannot.

Full planning costs an application fee and typically 8–13 weeks minimum in England (statutory periods vary). Refusal or conditions may require redesign. That sounds heavy, but building something that fails compliance is worse — enforcement, retrospective applications and resale blocks.

See a full-planning example on our Woolwich project.

Where does prior approval fit?

Larger home extension prior approval covers certain deeper single-storey rear extensions beyond standard PD depth but within an extended allowance. You notify the council; they assess neighbour impact — not full design merit.

Prior approval is not “full planning lite”. You must still meet PD conditions, and the council can refuse on impact grounds. Drawings must be accurate. We cover the process in our prior approval guide.

If prior approval is refused, you cannot build that scheme under PD — you would need to reduce depth or apply for full planning.

PD vs planning — practical comparison

| Factor | Permitted Development | Full planning | |--------|----------------------|---------------| | Application | Often none (or prior approval notice) | Required | | Decision basis | Compliance with rules | Policy, design, neighbour impact | | Typical pre-build time | Weeks | Months | | Flexibility | Low — must fit rules | Higher — negotiable within policy | | Resale proof | LDC recommended | Permission + compliance | | Risk if wrong | Enforcement, difficult resale | Refusal before spend |

Neither route guarantees build cost savings — see rear extension costs. The saving is usually time and certainty, not cheaper construction.

The role of an LDC

A Lawful Development Certificate is a council certificate confirming the work is lawful — either because PD applies or because planning permission exists. It is optional but valuable:

• Resale — buyers’ solicitors ask how the extension was authorised.
• Neighbour disputes — evidence the scheme was compliant when built.
• Insurance and mortgage — fewer questions when documentation is clear.

Read what is an LDC and GOV.UK LDC guidance.

Common mistakes that force a route change

• Measuring from the current house instead of the original as built.
• Ignoring Article 4 or estate conditions removing PD.
• Assuming conservation area only affects front elevations — side and rear rights can be restricted too.
• Loft dormers projecting beyond the roof plane facing the highway.
• Wraparound extensions combining rear and side without checking both rule sets.

Fix the route before detailed design. Redrawing after tender destroys budgets — a theme in build-only vs design & build.

How to decide in order

1. Property checks — listed? conservation? flat? PD removed? (Local authority property search helps.)
2. Concept size — will it fit PD or prior approval envelopes?
3. Quick tool — PD Quick Check.
4. Measured survey — accurate plans, not sketch dimensions.
5. Professional confirmation — book a consultation or commission an LDC pack.
6. Programme — map weeks in the timeline planner.

Next steps

• Run the PD Quick Check.
• Read Permitted Development basics on our hub.
• Compare delivered routes on projects.
• Book a consultation for a yes/no on your exact property and evidence list.