Basement Conversions in Marylebone, W1
Cellar and basement conversions in Marylebone: dry, habitable rooms below ground with designed waterproofing, natural light and building control approval.
Covered under one contract
- Structural design and calculations
- Planning or lawful development certificate
- New staircase, dormer and roof windows
- Insulation, fire safety and building control
- En-suite designed and fitted
- Waterproofing with guarantee for basements
Basement Conversions in Marylebone.
Where a house cannot grow outwards or upwards, it can grow downwards. Many of the older houses in Marylebone already have a cellar or vaults, and converting them into a usable floor is a well-established route to a utility room, guest suite, study or cinema room.
The two things that decide whether a basement works are waterproofing and light. We use a designed system, normally a cavity drainage membrane with a sump and pump, which carries a guarantee, and we bring light in through a lightwell or a rear opening where the site allows. Ceiling height, drainage and structure are all surveyed at the outset.
Converting an existing cellar without changing the exterior of the house does not usually need planning permission. Lightwells, listed buildings and new excavation do, and the central London boroughs have their own basement policies with impact assessments. All basements need building regulations approval and most involve party wall notices, which we prepare and serve.
- Area
- Marylebone, W1 · NW1
- Council
- City of Westminster
- Housing
- Georgian and early Victorian terraces, mews houses, mansion blocks and converted flats
- Transport
- Baker Street, Marylebone, Bond Street
- Basement, existing cellar
- 10 to 16 weeks
- Consent
- Often permitted development for lofts
- Waterproofing
- Guaranteed system, designed for the site
Marylebone: the houses and the planning rules.
Marylebone is where Space Cucina started, as a kitchen company on Seymour Place. The district is a grid of Georgian and early Victorian streets laid out by the Portman and Howard de Walden estates: flat-fronted brick terraces, stucco around the squares, mews houses behind, and the great mansion blocks of Marylebone Road and Baker Street.
Most of the housing is now flats, from mansion-block apartments to lateral conversions across two houses, which makes refurbishment here as much about approvals and logistics as about design: licences to alter, estate consent, parking suspensions and lift access all shape the programme. We have refurbished bathrooms on Marylebone Road and fitted kitchens for clients across the district.
The Portman Estate, Harley Street and Dorset Square conservation areas cover almost all of it.
Westminster City Council
Applications go to Westminster. Almost the whole district is within conservation areas, and many terraces are Grade II listed, so internal changes to listed houses need listed building consent.
Estate consent
On the Portman and Howard de Walden estates, the freeholder's own approval is needed in addition to planning, with their own design guidance for windows, roofs and rear elevations.
Mansion flats
Block rules govern working hours, deliveries and noise. We plan the programme around them and coordinate with the managing agent.
Approvals for basement conversions in Marylebone.
Converting an existing cellar without altering the exterior does not usually need planning permission; lightwells, listed buildings and new excavation do. Every basement needs building regulations approval and a designed waterproofing system, and most involve party wall notices.
Applications go to Westminster. Almost the whole district is within conservation areas, and many terraces are Grade II listed, so internal changes to listed houses need listed building consent.
What basement conversions in Marylebone includes.
- Structural design and calculations
- Planning or lawful development certificate
- New staircase, dormer and roof windows
- Insulation, fire safety and building control
- En-suite designed and fitted
- Waterproofing with guarantee for basements
From site visit to handover.
- 01
Site visit & consultation
We visit, listen and measure. Brief, budget and constraints understood before any advice is given.
- 02
Design & itemised quote
Our architects and engineers draw the scheme, and from that we provide a transparent, itemised quotation for your approval.
- 03
Planning & approvals
Planning applications, building control and party wall matters handled for you.
- 04
Build, managed weekly
Our own trades, sequenced by a site manager. Progress reported every week.
- 05
Handover & aftercare
Joint snagging walk-through, documentation, and a guarantee on our workmanship.
Basement Conversions in Marylebone: your questions.
Can I convert a cellar in Marylebone?
Usually. Converting an existing cellar without changing the outside of the house does not normally need planning permission. Lightwells, listed buildings and new excavation do, and every basement needs building regulations approval.
How do you keep a converted basement dry?
With a designed waterproofing system, typically a cavity drainage membrane with a sump and pump, or tanking where appropriate. It carries a guarantee and is designed for the ground conditions found on site.
Which parts of Marylebone do you cover?
All of Marylebone and W1 · NW1, including Seymour Place, Marylebone High Street, Montagu Square, Dorset Square, Harley Street, Baker Street, and the neighbouring districts. We are based in London and our teams work across central, north, north-west, west and south-west London.
Our work near Marylebone.
Other services in Marylebone.
House Refurbishment in Marylebone
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Flat Refurbishment in Marylebone
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House Extensions in Marylebone
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Structural Alterations in Marylebone
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Loft Conversions in Marylebone
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Kitchen Renovation in Marylebone
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Bathroom Renovation in Marylebone
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Bespoke Joinery & Fitted Furniture in Marylebone
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Architectural & Interior Design in Marylebone
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Planning Permission & Building Regulations in Marylebone
Read moreBasement Conversions across London.
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We will visit, listen and explain what is possible for your property and how it would be approved. No pressure, no sales pitch.