What Happens If I Build Without Planning Permission?

Do I always need planning permission?

Not always. Many small projects fall under Permitted Development (PD) – a national grant of permission with strict size, height and location limits. Start with our plain-English explainer:
What is the GPDO (Permitted Development)?

Useful primers for common home projects:

• Do you need planning permission for an extension?
• Side return extension — PD or permission?
• Maximum garden room size without planning permission
• Loft conversion — do you need planning permission?

Key point: PD only protects you if every relevant rule is met. If you exceed a limit, sometimes by centimetres, you need permission.

The most common ways homeowners get caught out

1. Assuming it’s PD without measuring properly. Typical slips: exceeding 50% garden coverage, breaching eaves/overall height near a boundary, oversizing a dormer.
2. Forgetting PD can be restricted or removed. In conservation areas, AONBs, or where there’s an Article 4 Direction, PD is limited. Read:
   Planning permission in a conservation area – a simple guide.
3. Flats/maisonettes ≠ houses. Most householder PD rights don’t apply to flats or homes created by change of use.
4. Confusing planning with building regulations. They’re separate regimes with different criteria. See:
   Planning permission vs building regulations.

Listed buildings: a special warning

Works (external and internal) that affect a listed building’s special interest generally need Listed Building Consent (LBC). Unauthorised works can be a criminal offence. Retrospective LBC may still be required and doesn’t erase liability. If there’s any chance your home is listed or within the curtilage of one, stop and get conservation-experienced advice immediately.

What actually happens if you build without permission?

1) Investigation

A neighbour complains or an officer notices works. You might receive a Planning Contravention Notice asking what’s been built and when. A site visit may follow to check PD compliance, conditions on past permissions, etc.

2) Possible outcomes

A) No further action. If the officer confirms it is lawful (e.g., within PD), the case may close. Consider a Lawful Development Certificate (LDC) to create a paper trail for future buyers and lenders.

B) Retrospective planning application invited. Councils must assess retrospective applications on their merits, just like a normal application. Expect validation checks, neighbour consultation and a target decision period. For timelines and smart preparation, see:
How long does a planning application take? and
What do I need for planning permission?.
To avoid common pitfalls, read:
How do I avoid planning permission refusal? 7 common mistakes.

C) Enforcement action. If permission seems unlikely, or you don’t engage, the council can serve an Enforcement Notice requiring alteration or removal within a set period. You can appeal, but strategy and evidence matter. They can also use (Temporary) Stop Notices to pause works, or Breach of Condition Notices if you had approval but didn’t follow a condition.

D) Building Control (separate). Even if planning is resolved, you may need to regularise the work with Building Control (open up works, test, or upgrade). Planning and building regs are independent.

“We thought it was Permitted Development” – typical fixes

• Side return too tall at the boundary or too long: tweak height/roof form to meet PD, or apply with a daylight/amenity case:
  Do you need planning permission for a side return extension?
• Garden room within 2m of a boundary over 2.5m high: lower the design, change roof, move location, or seek permission with justification:
  Maximum garden room size without planning permission
• Loft dormer oversize/forward of a highway roof plane: reduce volume or re-site; otherwise apply:
  Loft conversion — planning rules
• Rear extension slightly beyond PD limits: a well-prepared householder application may be your best option here.
  Do you need planning permission for an extension?

Time limits (“immunity”)

There are statutory time limits for taking enforcement action in England. The details depend on the type of breach and when it occurred. Don’t assume immunity without tailored advice, especially if you’re considering a Certificate of Lawfulness (Existing). Strong evidence (dated photos, invoices, sworn statements) is essential.

Will this affect selling or remortgaging?

Yes. Conveyancers and lenders typically ask for:

• Planning permission or permitted development evidence (ideally an certificate of lawful development)
• Building Control approval/completion certificates

Missing paperwork can stall a sale. If the works are otherwise acceptable, secure the right certificate or retrospective permission early.

What to do next (quick action plan)

1. Pause works if they’re ongoing. Avoid escalating the breach.
2. Measure and document: drawings, dates, photos, invoices.
3. Check designations: conservation area, Article 4, listed status. See:
   Conservation area – simple guide.
4. Choose the right route with a professional: retrospective householder application, LDC (Proposed/Existing), or redesign.
5. Submit a complete, policy-led package to speed validation and decision:
   What do I need for planning permission?
6. Plan the timeline and avoid common hold-ups:
   How long does a planning application take?
7. Get professional help early. A good architect can spot PD-friendly tweaks, prepare persuasive drawings/statements, and navigate consultations. To reduce risk, involve them before contacting the council formally.

Why involve an architect?

• Diagnosis: is the built scheme salvageable within PD or policy?
• Design tweaks: small dimensional changes can flip a refusal to an approval.
• Compliance & quality: accurate, to-scale drawings and a clear planning statement reduce objections and delays.
• Process handling: validation queries, conditions and officer liaison.

Ready to regularise works or start fresh? Post your brief on Design for Me to be matched with reviewed residential architects who know your local authority.