What is a basement conversion?
A basement conversion turns an existing cellar into living space, or excavates a new basement under the house or garden. Waterproofing, structural support and daylight are the main design challenges.
How much does a basement conversion cost in Enfield?
In Enfield, a basement conversion typically costs £2,450–£4,150 per m² for converting an existing cellar, including VAT at 20% (standard rate). For a typical 30 m² project that is roughly £73,500–£124,500. The guide for Enfield reflects typical costs in London, roughly 30% above the UK-wide figure. Design, structural calculations and council fees are extra.
| Size or type | Guide range |
|---|---|
| Smaller project (21 m²) | £51,500–£87,000 |
| Typical project (30 m²) | £73,500–£124,500 |
| Larger project (42 m²) | £103,000–£174,500 |
| Rate per m² | £2,450–£4,150 |
The main things that change the cost:
- Existing cellar or new excavation
- Floor lowering and underpinning
- Party wall surveyor fees
- Lightwells
For a figure based on your own measurements, try the guide price tool, then book a free home visit for a fixed quote.
Do you need planning permission for a basement conversion in Enfield?
Before anything is built in Enfield, we confirm which approvals apply in England. In England converting an existing cellar with no external change usually does not need planning permission. New excavation, lightwells and changes to the front often do, and some councils, particularly in London, have specific basement policies.
Building regulations approval comes from the council’s building control service or a registered building control approver. The work is inspected at key stages, such as foundations, drainage and insulation, and a completion certificate is issued at the end.
Our first visit includes a check of your planning history, so you know the route before paying for drawings.
What we handle
From survey to sign-off, the job normally involves:
- Lightwells and windows
- Waterproofing design (tanking or cavity drain membrane)
- Insulation, ventilation and drainage pumps
- Building control sign-off
- Electrics, heating and plastering
- Underpinning or new structure where needed
How long does it take?
Allow 8 to 16 weeks for a cellar conversion; longer for new excavation. Before that, surveys, drawings and approvals usually take 3 to 5 months, longer if the council asks for changes.
Building in Enfield
Victorian and Edwardian terraces dominate many London streets, which is why side return, wraparound and mansard projects are so common here.
Projects in Enfield (EN1 and EN2) are surveyed in person before we quote, so the price reflects your actual property.
How it works
- 01
Free visit
We look at the property, talk through what you want and measure up. There is no charge and no obligation.
- 02
Design and fixed quote
Drawings, structural calculations and an itemised, fixed price for the agreed specification.
- 03
Approvals in place
We handle planning, building control and neighbour notices before work starts.
- 04
Build and handover
Work follows the agreed programme, with inspections along the way and a completion certificate at the end.
Questions about basement conversions in Enfield
How long does it take?
A cellar conversion takes around 8 to 16 weeks; new basements take longer.
Do I need party wall agreements?
In England and Wales, excavating near a neighbour’s foundations usually triggers the Party Wall etc. Act 1996.
Do you build basement conversions in Enfield?
Yes. We build basement conversions across Enfield, including postcodes EN1 and EN2. Every project starts with a free home visit.
How much does a basement conversion cost in Enfield?
In Enfield, a basement conversion typically costs £2,450–£4,150 per m² for converting an existing cellar, including VAT at 20% (standard rate). A typical 30 m² project comes to roughly £73,500–£124,500. Your fixed price depends on the survey and drawings.
Does a basement conversion need planning permission?
Converting an existing cellar without changing the outside usually does not. New excavation, lightwells and changes visible from outside usually do.