London’s Leading Basement Conversion Specialist

Basement conversions in London

In the last few years, London’s homeowners have been looking to dig down in order to create basement paradises. With space becoming a rare commodity and property prices in central London rising to be some of the most expensive in the world, it’s not surprising that the capital’s residents are looking to improve not move.

While mega and iceberg basements have been stealing the headlines, most basement conversions are not billionaire wonderlands, but practical areas used by families wanting more space. One of the driving factors behind London’s basement boom is the fact that many of the capital’s most sort after postcodes are protected heritage areas. This means homeowners cannot extend up or out – but they can extend down.

Since the basement craze took off in around 2011, the rules surrounding basement conversions have changed. Read our guide below to find out what you need to do to get your London basement conversion underway in 2017.

Planning permission for a London Basement conversion

Planning permission differs from borough-to-borough, however, in some of London’s swishest neighbourhoods the council are clamping down on large-scale basement excavations. The Royal Borough of Kensington and Chelsea and Westminster, amongst others, have changed their planning laws after a slew of complaints from residents and businesses.

Almost all London basement conversions need planning permission, however, there are rare circumstances where it may fall under permitted development. Typically you will need some or all of the following permissions:

  • Planning permission
  • Building control
  • Listed building consent
  • Party Wall Agreement
  • Highway licence
  • Skip licence
  • Parking suspension
  • Streetworks licence
  • Freeholder consent (if you live in a flat or leasehold house)

Your basement project may be refused planning permission because of ‘over-development.’ What this actually means can be wide ranging. The London Borough of Richmond-upon-Thames describes it as ‘Just as overly large extensions above ground level can dominate a building, an extension below ground can be of an inappropriate scale.’

Other things you may need to think about are:

  • Tree and root protection: if you damage street trees or ones on adjoining sites some boroughs may refuse your application.
  • Drainage and rainwater: A basement development may have to provide an appropriate proportion of planted material to allow for rainwater to be absorbed.
  • Basements being used as living accommodation: if you plan on using your basements to house living accommodation, such as family or staff bedrooms you may need to ensure the rooms have sufficient daylight, outlook and privacy.

For a more detailed look at planning for a London basement conversion take a look at our planning permission page.

The Triple conversion

Simply Basement is the sister company of Simply Extend and Simply Loft. This mean the Simply Construction Group are well placed to take on a triple conversion, which includes loft, extension and basement conversions. We are an end-to-end provider and will guide you through the planning, design and build process.

Cellar conversions

Many historical properties in London already have cellars. This offers the home owner the option of converting what used to be a storage space into a liveable space. Depending on what you plan to use the space for you may not have to ask for planning permission, however, if you wish to turn your cellar into a basement flat, this will require planning permission.

What are the steps to getting a basement conversion in London?

There are three main steps to basement conversions. These include

  • Design and planning process
  • Structural phase
  • Fit-out

Design and Planning process

The first part of this process is the site survey. A surveyor from Simply Basement will come and visit the property and will be able to advise if a basement conversion is feasible for your home. If the project is feasible, the surveyor will give advice on what can be achieved and will take measurements for a quotation.

Once this is done, a quote and specification will be supplied and a contract drawn up. Simply Basement quotas are divided into two parts, one is for the design and planning process and the second is for the fit out. Once the contract is signed, the design and planning process can then take place.

If your property has a wall connected to another property or it’s detached and the basement conversion comes within 3m of their property, a Party Wall Agreement will need to be sorted. At Simply Basement, one of our certified party wall surveyors will help you through this process.

Once the planning permission and Party Wall Agreements are in place, the construction phase can begin. On average it can take between 6-10 months to complete a basement conversion.

Structural phase

This part of the process involves the following:

  • Securing the site with hoarding
  • Weatherproofing
  • Ensuring it passes all health and safety requirements
  • Securing the Underpinning
  • Digging out the soil and disposing of it correctly

Once all the above have been completed, it is time to waterproof the basement. This is usually done with sump and pump drainage systems and at Simply Basement, we also add a delta membrane system. If your specification includes any lightwells or windows, it is in this phase that they will be installed.

Basement Fit out  

When the structural phase is complete – it’s time for Simply’s fit out team to take over. This means transforming the shell into liveable space. What will be done and how long this will take is dependent on your specifications, but as a rough guide, here is what will be completed:

  • Utilities such as gas, electric and plumbing will be installed
  • The flooring will be finished, including any underfloor heating
  • Any bespoke carpentry and joinery are carried out
  • Pool, bathroom or kitchen installation
  • Any other specifications that need to be added

At the end of this phase, one of our Simply Basement representatives will meet with you to give you your completion pack. This includes details of all guarantees, your gas and electrical safety certificates and building control sign-off.

If you want more basement inspiration then please visit our blog. If you are thinking of converting your basement then contact us for a free site survey.


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