Basement Extensions

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Our Services for Basement Extensions

Basement extensions are a great solution if extending out or upwards is not a feasible option. This is often the case in London where development regulations, or a lack of space, can prevent them. Or maybe you have already got a loft conversion London, single storey extension, or double storey extension but still need more room. A basement extension can create new rooms with unique qualities.

From an architectural perspective, undergroumd spaces may not be ideal for a kitchen or dining room because of the limited natural light and views but they are certainly useful for entertaining spaces such as cinema rooms, childrens playrooms or even swimming pools.

Basement extensions are fast becoming the most popular type of home extension in London and even if you don’t have a basement you can still have a basement extension by excavating down. At EA our Architects in London have extensive knowledge when it comes to making your house extension come to life. Take a look at our case studies below or get in touch with us for more information.

Frequently Asked Questions about Basement Extensions

What’s the cost of a Basement Extensions?

The cost of your basement extension will depend on various facotrs such as the building type, size, location, geology and whether or not it is in a conservation area. the Basement Waterproofing Association has provided the most recent costs involved when considering extending your basement:

  • Conversion of existing basement: £900 – £1,400 per square metre
  • Lowering the floor level of an existing basement: £1,500 – £2,000 per square metre
  • Digging a new basement space and underpinning: £2,500 – £3,000 per square metre
  • Digging a new basement: £1,500 – £2,000 per square metre
  • Creating a light well or external access: £5,000 – £7,500 per square metre
  • Planning application council fees (if required) : £206 (householder application), £462 (if new unit of accommodation is proposed)
  • Building Regulations application At least £750
  • Party Wall agreement (if required) At least £700 per neighbour
  • Additional tax if using VAT-registered contractors +20%

Do I need planning permission for Basement Extensions?

If you are planning to convert your existing basement wihtout having to excavate, or change the external appearance of the property then it is not likely that you will need planning permission. However, if you are planning to retrofit your existing basement, by adding light, ventilation or additional structural elements then you will need planning permission. This of course applies to creating a whole new basement all together, planning permission amoungs other mandatory SPD (Supplimentary Planning Documents) will be required. You should always check with your local planning authority to see what information they require, as there are a lot of surveys and assessments that need to be carried out to determine the viability of basment construction, so it is always best to be prepared.

Will a Basement Extension add property value?

A basement extension can increase the value of your home by up to 30%, for example in areas like Hammersmith and Fulham, where space is few and far between, converting a basment if the most popular type of extension. However, there are a few things you need to check out which will give you an indication of how much your cellar conversion is likely to cost. (Remember, you are likely to need a surveyor or architect to help you with some of these investigations.

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