Professional, builder-ready drawing packages for extensions, lofts, porches, garages, garden rooms and more — designed to Permitted Development parameters and supplied as sold.
PERMITTED HOMEOWNER GUIDES
Our illustrated, practical guides help you understand the rules, explore design options and budget with confidence — before you commit to building work.
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Rules, design options, costs and next steps.
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Rules, design options, costs and next steps.
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Rules, design options, costs and next steps.
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Rules, design options, costs and next steps.
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Rules, design options, costs and next steps.
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Rules, design options, costs and next steps.
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Rules, design options, costs and next steps.
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Rules, design options, costs and next steps.
View guideBasement extensions usually need planning permission — but converting an existing cellar may not. Here’s when basement works require consent, what councils assess, and what they cost.
Converting an existing basement into habitable space (where no new excavation is involved and the external appearance is unchanged) may be permitted development. However, most basement extensions involve new excavation, creation of a lightwell, or changes to the external appearance — these require planning permission. In London, councils have adopted strict basement extension policies due to concerns about structural risk, flooding, and impact on neighbours.
| Type of Work | Planning Status |
|---|---|
| Converting existing cellar to habitable room | May be PD if no external changes. Building regs required. |
| Excavating new basement (no external changes) | Usually development requiring planning permission |
| Basement with new lightwell or external staircase | Planning permission required |
| Basement with separate access/entrance | Planning permission required |
| Basement beneath a new extension | Assessed as part of the extension application |
Many London councils limit basement extensions to one level below ground, restrict the footprint to 50% of the garden, require Basement Impact Assessments, and restrict basement extensions in flood zones.
All basement works need building regulations approval: Part A (structure/underpinning), Part C (waterproofing/tanking), Part F (ventilation), Part L (insulation), and Part M (access).
| Item | Approximate Cost |
|---|---|
| Basic cellar conversion (no excavation) | £20,000–40,000 |
| New single-level basement (inner London) | £80,000–150,000+ |
| New basement with lightwell and staircase | £100,000–200,000+ |
| Planning and structural fees | £10,000–30,000 additional |
| Party wall surveyor fees | £1,500–5,000 per affected neighbour |
This kind of project usually needs planning permission rather than permitted development. PERMITTED is part of YPDS Architectural Services, a Leeds architectural design practice that designs, prepares and manages planning applications.
Planning a project? Browse our permitted development drawing sets — fixed price, supplied exactly as sold and emailed to you as a PDF.
Each one is already drawn. You choose the material, roof and options we actually draw, and that is the package you receive.
A practical entrance area that adds space and improves the look of your home.
£350
A popular way to create a larger kitchen, dining or family area.
£900
Adds valuable space to the side of your home for a kitchen or utility.
£900
Turns unused loft space into a bedroom, office or additional living area.
£1,500
A flexible, detached space for work, leisure or extra living space.
£350
Secure parking or useful storage, single or double.
£350
Significantly more living space across both floors.
£1,400
A bright, glazed room connecting your home to the garden.
£900PERMITTED HOMEOWNER GUIDES
Our illustrated, practical guides help you understand the rules, explore design options and budget with confidence — before you commit to building work.
Explore all guidesRules, design options, costs and next steps.
View guideRules, design options, costs and next steps.
View guideRules, design options, costs and next steps.
View guideRules, design options, costs and next steps.
View guideRules, design options, costs and next steps.
View guideRules, design options, costs and next steps.
View guideRules, design options, costs and next steps.
View guideRules, design options, costs and next steps.
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Maximize your property’s footprint with precision and ease. Permitted provides complete design for Permitted Development Rights. Our packages are designed around the Permitted Development limits, so many projects can proceed without a full planning application.
PERMITTED is operated by Yorkshire Property Design Services Limited, registered in England and Wales under company number 12698267.
Registered office: Ground Floor, Techno Centre, Station Road, Horsforth, Leeds, LS18 5BJ
Business contact address: Wira House, Ground Floor, Suite 5, Ring Road, West Park, Leeds, LS16 6EB
