Basement Conversions

Basement Conversion London
Converting a Basement

Converting or extending the basement to a home provides valuable extra living space without transforming the house’s exterior. The basement is close to the main living areas and has a more flexible range of uses. There is no right or wrong way to set up space. You have to focus on what you want and decide what your highest priority is. Start by listing the functions of the new space and what size area you will need to accommodate it. Will there be a kitchen? Will the room be a bedroom, an office, a family room, or a home theatre? Is there going to be a bathroom? Will it be a home gym? Do you need separate rooms for all those purposes? All of these types of rooms have specific dimensions and requirements. List those out in a short “program.”

Bacement - copy
Garden - copy
Dining - copy
Cinema Room - copy
Kinchen_3 - copy
previous arrow
next arrow
Bacement - copy
Garden - copy
Dining - copy
Cinema Room - copy
Kinchen_3 - copy
previous arrow
next arrow

Typical process of basement conversion:

Initial Consultation

You will meet up and discuss your needs with a basement specialist or architect. You may find it easier to make a list of questions beforehand, which you can refer to and make notes on, indicating the costs involved.

Design and Planning

A complete survey of the property is carried out, and a design for the proposed basement is created.

Good quality design is an integral fundamental part of sustainable development. As a matter of fact, a good design responds in a practical, creative way to the function and identity of the place. Once the design has been agreed upon, the planning permission application is submitted.

You must tell your neighbours if you want to conduct any building work near or on your shared property boundary. Basement specialists or architects will arrange a Party Wall surveyor to contact neighbouring properties to achieve a Party Wall award. The Party Wall Act provides a legal framework for preventing and resolving disputes in relation to boundary walls, party walls and excavations near neighbouring buildings.


Work on the basement starts by digging and removing soil. Underpinning and reinforced concrete works are being carried out, and steel beams are erected as required to support the house’s existing structure. Basement conversions are not a DIY job because of the risk of undermining the foundations, leading to instability or even the collapse of the supporting walls.

Basement excavation and structural works will be followed by waterproofing the structure reconfiguring drain runs and existing utility holes. There are several ways to waterproof the structural walls of a basement. The specific method used will depend on the ground conditions and the type of construction. It is likely to be tanking, using some form of a membrane, such as bonded sheet or cavity drain membranes.

Basements are naturally well insulated by the earth surrounding them but still will require additional insulation to meet Building Regulations requirements.


The key considerations for the first stage of the fitting-out process are space, comfort and light. Basement fit-out will involve everything from the insulated screed or polished concrete covered floors, electrics, plumbing, first and second fix items such as joinery, doors and painted finishes, organising the lighting scheme, and finally adding the furniture.

How much does a basement conversion cost, and how long will it take?

Inarguably, project price depends on the size of the property, the amount of excavation and building work required and its complexity. In fact, significant factors that add costs to the project are needs to divert drains, challenging or poor ground conditions, access to the site etc. Also, the price of fitting a basement reflects on the quality of the work undertaken.

Here’s a rough estimate of the costs involved:

  • Conversion of existing basement – £2,000 – 2,500 per m²
  • Lowering floor level and underpinning an existing basement – £2,000 – 2,500 per m²
  • Digging new basement space and underpinning – 2,500 – 3,500 per m²
  • New basement space beneath the garden – £2,500 – 3,500 per m²
  • Creating a light-well / external access – £8,000 – 15,000
  • Engineers fees – £1,500 – 2,000
  • Planning application – £172
  • Building Regulations application – £750 + according to the value of works
  • Party Wall surveys – £700 per neighbour
  • VAT – 20% added by a VAT-registered contractor

A high price is not necessarily a sign of quality in a building firm. But, more than that, it is essential to resist the obvious temptations of a low price. If one firm comes back with a quote for your work significantly lower than the other tender prices, you need to be suspicious.
Although projects must meet their cost, time and quality targets, project success can be defined in many ways, but investing in professional project management and controls can yield some very substantial benefits.

Should you require any further help or assistance, please do not hesitate to contact us.

Leave a Reply

Your email address will not be published.