The UK Planning Knowledge Base
Straight answers from a chartered town planning practice — not a content agency, not a chatbot, not a law firm. Guides and FAQs organised by topic, covering the questions that decide most applications in England.
Planning permission & the decision process
How applications are decided, why they're refused, and what to do when the answer is no — from the Local Plan and material considerations through to enforcement and appeals.
How long does a planning application take in England?
Statutory timescales, why most applications run over, and the single most effective thing to do before submitting.
Is pre-application advice worth it?
What a pre-app actually buys, when it's worth every penny, when skipping it is the right call, and what it costs in 2026.
The cost of guessing: 5 fatal mistakes before submitting
Designing before the route is confirmed, paying for drawings before testing policy, and treating validation as a formality.
Do neighbour objections stop planning permission?
What counts as a material objection, why the number of letters decides nothing, and how AI-written objections are changing consultation.
What happens if you build without planning permission?
Enforcement notices, retrospective permission, the ten-year immunity rule, and how an unauthorised build blocks sale and remortgage.
What to do the moment your application is refused
How to read a decision notice, the three routes open to you, the two costly mistakes to avoid, and a calm plan for the first week.
How to beat a planning refusal notice
Appeal, amend or resubmit — how a householder appeal works, what makes one succeed, and when resubmission is the faster route.
Under s.38(6) PCPA 2004 applications must be determined in accordance with the development plan unless material considerations indicate otherwise. Common avoidable causes: not reading Local Plan policies before commissioning drawings; missing supporting documents; unaddressed environmental constraints — all checkable for free before submission.
Refusals are predictable, not random. Every application is assessed against five categories: policy compliance, design quality, amenity impact, highways, and environmental constraints. Miss any one and the officer has a well-founded reason to refuse.
1. No pre-submission neighbour engagement. Talk to neighbours, document it, address what you can, and include the engagement in your planning statement.
2. Design that doesn't fit its context. Scale, massing and materials must respect the surrounding area. The design and access statement must justify the design concept, not merely describe the proposal.
3. Unaddressed environmental constraints. Protected trees, flood zones, ecology and contamination are all checkable for free. They are not surprises — they are failures of preparation.
Under s.38(6) PCPA 2004 all applications must be decided in accordance with it. It sets out where development goes, density requirements, design standards, affordable housing percentages and environmental designations. Read it before commissioning drawings.
If a council's Local Plan is more than five years old without active review and cannot demonstrate a five-year housing land supply, the plan may be out of date — triggering the presumption in favour of sustainable development under NPPF Para.11.
Material: policy compliance, design quality, amenity impact including overlooking, overshadowing, loss of light and noise, highways, flood risk, ecology, heritage and public benefit.
Not material: effect on property values; personal disputes; competition concerns; moral objections; general opposition to change. A committee that refuses on non-material grounds exposes the council to a costs award at appeal.
The officer's response identifies whether the principle is acceptable, which policies apply, what documents are required, and what design changes would strengthen the application. A response on file is also a material consideration. Book it before the architect produces detailed drawings.
The council can serve a Planning Enforcement Notice requiring demolition within a compliance period. Non-compliance is a criminal offence with an unlimited fine under s.179 TCPA 1990.
Practice note: Immunity is not a planning strategy. Since 25 April 2024, s.115 of the Levelling-up and Regeneration Act 2023 applies a single ten-year time limit to breaches in England — replacing the old four-year rule for operational development and change of use to a single dwellinghouse. The four-year period survives only where a breach had already become immune before that date. Either way, immunity requires documentary evidence of continuous use that most homeowners do not have.
Permitted development rights
What can be built without a full application — and the situations where those automatic rights are restricted or removed.
What is permitted development and what are its limits?
Automatic PD rights versus prior approval, the limits in numbers, the "original dwellinghouse" trap, and a PD calculator.
What is an Article 4 Direction and how does it affect me?
How councils remove PD rights, where to check if one applies, and what happens if the work goes ahead anyway.
1 in 5 prior approvals are refused: the 5 most common mistakes
What the council can and can't assess under prior approval, the timescales, and what happens if they don't respond in time.
Change of use & the Use Classes Order
The current use classes, when permission is needed, the changes you can make without applying, and what it costs.
What a lawful development certificate actually proves
What a certificate proves and what it doesn't, the proposed-use and existing-use routes, and what it costs in 2026.
- Detached houses: up to 8m rear extension under prior approval; up to 4m without.
- Semi-detached and terraced: up to 6m under prior approval; up to 3m without.
PD rights do not apply if the property is listed, an Article 4 Direction applies (common in conservation areas), conditions on the original permission removed them, or previous extensions used the allowance. A Certificate of Lawful Development provides formal written confirmation and is strongly recommended even where PD rights clearly apply.
Green Belt & land designations
What the Green Belt actually is, the grey belt category under the December 2024 NPPF, and the designations that genuinely protect landscape and ecology.
Can you build in the Green Belt? Grey Belt & the NPPF 2026 reforms
Very special circumstances, the exceptions that already permit development, and what the draft 2026 reforms could change.
National Landscapes (AONBs): what the designation means
The law behind the designation, the stronger duty introduced in 2023, and what remains permitted development.
SSSIs and protected sites: what it means for homeowners
What an SSSI restricts, building near a protected site, where Biodiversity Net Gain fits, and the 2025 reforms.
England has 1.6 million hectares of Green Belt. A significant proportion is scrubland, degraded agricultural land, golf courses and car parks — receiving almost the same planning protection as a National Park despite a fraction of the ecological value. The designations that actually protect landscape and ecology are National Parks, National Landscapes (formerly AONBs) and SSSIs — separate designations with separate legislative bases.
The December 2024 NPPF introduced grey belt: lower-quality Green Belt land to be released before higher-quality land, under NPPF Para.152.
Heritage & conservation
Listed buildings, conservation areas and curtilage — the extra layer of control that applies to historic and protected properties.
Listed building consent: what you can and can't do
Whether the listing covers the interior, what always needs consent, and the grey areas — kitchens, windows, walls and doors.
Living in a conservation area: what changes
The PD rights you lose, when Article 4 applies, and the rules on demolition, trees and materials.
What counts as curtilage — and why it matters
How curtilage is decided, and why it determines whether an outbuilding or boundary falls under listing or PD control.
Project-type guides
Practical, project-by-project guides. Each one links up into the policy pillars above — because most real projects touch several at once.
Do I need planning permission for a rear extension?
PD size limits, the 42-day prior approval procedure, and a decision tree for detached, semi and terraced houses.
Do I need planning permission for a loft conversion?
Volume allowances, when a dormer needs full permission, and the rules for terraced houses and Article 4 areas.
Do I need planning permission for a garden room?
Height and area limits, using a garden room as an office or annexe, and when it stops being permitted development.
Do I need planning permission for a side extension?
The boundary rules most people miss, the width restriction, and where a side extension tips into full permission.
Do I need planning permission for a garage conversion?
What officers check first, when conversion is permitted development, and the parking and Article 4 traps.
Do I need planning permission for a two-storey extension?
How the harm test is applied, the 45° and 25° measuring tools, and how to design the harm out before submitting.
Do I need planning permission for a porch?
The three PD limits, when a porch needs full permission, building regulations, and what it costs to get wrong.
Barn conversions & Class Q
What Class Q permits, what changed in 2024, where it does not apply, and why conversion is not rebuild.
Do I need planning permission for a dormer?
The difference between a dormer built under PD and one that needs full permission, explained with the volume limits.
Not sure where your application stands?
Start with the free assessment — 15 questions, a personalised risk score, no sign-up required. Then go deeper with a Snapshot or a one-to-one session.
Note: General guidance for England under NPPF December 2024, updated 2026. Written and fact-checked by a chartered town planner. Does not constitute professional planning advice — always take tailored advice from a chartered town planner before submitting an application or commencing works. PlanWiser · Chartered Town Planning Consultancy · planwiser.uk