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Projects Planning Permission Checker Party Wall Checker House Extension Cost Loft Conversion Cost HMO Conversion Cost Office Fit-Out Cost Areas We Cover Get a QuoteDo you need planning permission?
Answer a few quick questions about your property and the work you're planning — get an indicative answer in under two minutes, free.
The limits are stricter than they look
Many extensions, loft conversions and outbuildings don't need a full planning application — they fall under Permitted Development, a set of national rules that grant automatic permission within set limits. The catch: those limits are strict, and going a few centimetres over changes the outcome entirely.
Answer a handful of quick questions about your property and the project you're planning, and we'll check your answers against the national size, height and boundary limits — telling you exactly which rule your project is being measured against, not just a general yes or no.
Please read before you start: this checks your project against the main national Permitted Development limits for England. It can't see your actual property, its planning history, or any local restrictions that might apply — treat the result as a starting point, not a final answer. Confirm with your local planning authority or apply for a Lawful Development Certificate before starting work.
Step Through It
Six quick questions, then an indicative answer for your specific project.
What type of property is it?
Is the property a listed building?
Is the property in a conservation area, Article 4 direction, National Park, or AONB?
What are you planning to build?
The dimensions
"Original" means the house as first built (or as it stood on 1 July 1948) — not as it is now if it's already been extended.
Reference Guide
What's allowed under Permitted Development
Based on the Town and Country Planning (General Permitted Development) (England) Order 2015 — these rules have been broadly stable since 2015 and are unchanged as of 2026. Always confirm your specific case with a Lawful Development Certificate.
Single-storey rear extensions
Usually Allowed
- Up to 4m deep (detached) or 3m (semi-detached/terraced) under standard PD
- Up to 8m (detached) or 6m (semi-detached/terraced) under the Larger Home Extension Scheme, via Prior Approval
- Materials similar in appearance to the existing house
Usually Needs Full Planning
- Eaves height over 3m if within 2m of a boundary
- Extending beyond the Larger Home Extension Scheme limits
- Building forward of the principal elevation facing a road
Double-storey rear extensions
Usually Allowed
- Up to 3m deep — same limit for detached, semi-detached and terraced (no Larger Home Extension Scheme option)
- At least 7m from the rear boundary
- Ridge and eaves no higher than the existing house
Usually Needs Full Planning
- Depth over 3m — no larger-extension route exists for double-storey
- Within 7m of the rear boundary
- Upper-floor side windows that aren't obscure-glazed and non-opening below 1.7m
Side extensions
Usually Allowed
- Single storey only
- Max width: 50% of the original house's width
Usually Needs Full Planning
- Two-storey side extensions
- Any side extension in a conservation area — automatically excluded from PD regardless of size
- Width over 50% of the original house
Loft conversions
Usually Allowed
- Up to 40m³ additional roof volume (terraced houses)
- Up to 50m³ additional roof volume (semi-detached/detached)
- Materials similar in appearance to the existing roof
Usually Needs Full Planning
- Exceeding the existing roof ridge height
- Dormers facing a road, in most conservation areas
- Volume beyond the terraced/semi-detached limits above
Outbuildings & garden rooms
Usually Allowed
- Single storey, eaves height up to 2.5m
- Overall height up to 4m (dual-pitched roof) or 3m (any other roof)
- Total outbuilding coverage up to 50% of the garden
Usually Needs Full Planning
- Used for sleeping accommodation (a "garden office" with a bed is not PD)
- Coverage exceeding 50% of the garden combined with other extensions
- Positioned forward of the principal elevation
Always removed regardless of size or type: listed buildings (need planning + listed building consent), flats and maisonettes (no PD rights for extensions at all), and any property where an Article 4 direction has specifically removed these rights — common in around 30% of conservation areas.
Not Sure?
Get a definitive answer, not just an indicative one.
Book a free consultation and we'll assess your specific property and project — including checking for any Article 4 directions or conservation area restrictions that affect it.
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Areas We Cover
Based in Manchester, working across the wider North West on design & build, windows & doors, and networks & security projects.
- Manchester
- Salford
- Stockport
- Trafford
- Bolton
- Bury
- Oldham
- Rochdale
- Warrington
- Cheshire