The process of building a basement

Initial consultation

You will sit down with your basement specialist or architect and discuss your needs for the proposed project. You will then be given an indication of the costs involved and offered a quotation for the structural and fit-out aspects of the work.

Design and planning

A full survey of the property is carried out and a design for the proposed basement is created. Once a design has been agreed, the planning permission application is submitted (which should take approximately eight weeks).

While waiting for planning approval, your basement specialist or architect will appoint a party wall surveyor to serve notice on the neighbouring properties and obtain the party wall award. Once the Party Wall award and planning permission has been obtained, you will then receive an idea from your specialist on the timeframe for each phase of the project, along with the final time for completion.

Building

Work on the basement is started by digging and removing any soil, with any underpinning works carried out, and reinforced concrete and timber or steel beams erected as required to support the structure of the existing house, following the guidance of a structural engineer. The basement excavation will involve supporting the existing foundations, the internal loadbearing walls, floors and any concrete pads that may be supporting an existing extension.

This will then be followed by waterproofing the structure and reconfiguring drain runs and existing manholes, to ensure that you are left with a waterproof shell that’s ready for the next stage of fitting the basement out.

Fit-out

The fit-out starts with the insulated, screed-covered floor, which then takes carpet, wood flooring or tiles. After that come the electrics, the plumbing, and the first and second fix items such as joinery, doors and painted finishes, all of which have to comply with Building Regulations. Then the lighting scheme, and finally the furniture.

With every square foot of living space at a premium in London, digging down is often the only direction left. NU Projects excavates, converts and builds basements under occupied London houses, and coordinates the planning, the party wall process and the structural design in the same contract.

Before you appoint anybody, read the ten checks worth making. To talk about a specific property, tell us about it, and to price the work use the cost calculator.