Structural & Groundworks
Foundations, excavation, drainage, underpinning and structural alterations, matched to a groundwork contractor near you.
Basement Conversions In London, Dug, Tanked And Signed Off
Cellar conversions, full dig outs, underpinning and waterproofing. Send the property detail and we route it to a basement specialist.
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Basement Conversions In London
A basement is the most technically demanding way to add space to a London house and the most heavily engineered. It involves taking load off the existing foundations, lowering the ground beneath them in a controlled sequence, and then keeping water out of a room that sits below the water table.
There is a real difference between converting a dry cellar that already exists and excavating new space under a house. Tell us which you have. The structural side runs with groundwork and underpinning, and on a project this size quantity surveying earns its fee.
Cellar Conversion Or Full Dig Out
These are two different projects that get given the same name. The first is a refurbishment; the second is a major structural operation.
- Converting an existing cellar with adequate height
- Lowering the floor level within existing walls
- Full excavation beneath the footprint
- Extending the basement beyond the house under the garden
Underpinning And Structure
The house has to stay up while the ground under it is removed. That is done in short engineered bays to a sequence the engineer sets, and it is not an area for improvisation.
- Sequenced underpinning in numbered bays
- Reinforced retaining walls and a structural slab
- Temporary propping throughout the works
- Party wall awards with every adjoining owner
Waterproofing And Natural Light
Below ground, waterproofing is a designed system rather than a product, and it is normally specified by a specialist and guaranteed by them.
- Cavity drain membranes with sump and pump
- Backup pumps and power for the drainage system
- Lightwells and a compliant means of escape
- Drainage, tanking and damp protection throughout
How A Basement Conversions Enquiry Runs
Tell Us What Is Down There
Whether there is an existing cellar, roughly what head height it has, and the property type. Photographs of the space if you can get them.
We Match A Specialist
Basement work is specialist and it is insured differently. The enquiry goes to a contractor who does it, not a general builder.
They Assess Feasibility
They look at the structure, the ground and the neighbours before pricing, because on this job feasibility comes before cost.
Find Out If A Basement Is Feasible
Send the property detail and what is under it now, and a basement specialist will come back to you.
The Kind Of Work That Comes Through
Surveying, structure, extensions and finishing across London property.
Where We Work
RCRO Building works across London and the towns and villages within 20 miles.
Towns And Villages
- London
- City of Westminster
- Islington
- Chelsea
- Battersea
- Holloway
- Brixton
- Peckham
- Fulham
- Archway
- Shepherds Bush
- Canary Wharf
- Stamford Hill
- Willesden
- Cricklewood
- Putney
- Streatham
- Stratford
- Chiswick
- Catford
- Canning Town
- Acton
- Wimbledon
- Tottenham
- Finchley
- Leytonstone
- Walthamstow
- Mitcham
- Wembley
- Beckenham
- Brent
- Morden
- Edmonton
- Eltham
- Croydon
- Barking
- Ilford
- Carshalton
- Enfield Town
- Chingford
- Greenford
- Harrow
- South Croydon
- Hounslow
- Welling
- Southall
- Thamesmead
- Heston
- Surbiton
- Sutton
- Becontree
- Purley
- Borehamwood
- Ewell
- Bexley
- Hayes
- Dagenham
- Feltham
- Banstead
- Ruislip
- Epsom
- Cheshunt
- Esher
- Romford
- Dartford
- Watford
- Uxbridge
- North Watford
- Staines
- Leatherhead
- Hatfield
- Hoddesdon
- Redhill
- St Albans
- Grays
Basement Conversions Questions
What is the difference between a cellar conversion and a full dig out?
A cellar conversion uses a void that already exists: tank it, light it, finish it. A full dig out excavates new space beneath the house, which means underpinning the existing foundations and building a new retaining structure. The second is several times the work of the first.
Do I need planning permission for a basement conversion?
Converting an existing cellar often does not, but excavating a new basement usually does, and many London boroughs have specific basement policies with their own limits and required reports. Check your own borough's policy early, because they differ considerably.
Will underpinning damage my neighbours' property?
Done to a proper engineered sequence by a specialist, it should not, which is exactly why the sequence is designed rather than improvised. The Party Wall Act applies: notices are served, neighbours can appoint their own surveyor at your cost, and a condition survey records their property beforehand.
How is a basement waterproofed properly?
Current practice is a designed system rather than a coating, most commonly a cavity drain membrane that collects water behind the wall and takes it to a sump and pump. Backup power and a maintenance regime are part of the design, not optional extras.
What ceiling height can I realistically achieve?
It depends how far you can go down, which is governed by the foundations, the ground and the water table rather than by preference. The specialist will tell you what is achievable on your property after looking at it.
How long does the work take from survey to completion?
Longer than almost any other domestic project. The surveys, engineering, planning and party wall awards all happen before excavation starts, and the underpinning itself proceeds bay by bay by design.
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Quantity Surveying
Cost planning, procurement and commercial management on London projects, from feasibility through to the final account.
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