Expand the size of your home by converting your basement into a living space - here's our basement conversion and cellar conversion cost guide.
How much does a Basement Conversion cost?
Average cost in UK: £1216
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The average cost for a basement conversion is £1216. You are likely to spend between £750 and £10000 total. Exact price may vary depending on your area and project details.
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Cost Summary for Basement & Cellar Conversions

Price Range = £750 to £10,000+

Average Cost = £1,216.00

Cheapest Price = £750

If you have additional, unused space in the form of a basement or cellar, or simply fancy extending your new home but have no option but to start digging below the current floor level, then you may want to look into a basement or cellar conversion as a way of adding value to your property and improving your standard of living.

A basement could make a great extra living room, or even a games room, home cinema or kids play area if you fancy something a little more exciting. But if you do need the extra space, it could also make a great storage area or utilities room too. If you have a lot of work to be getting on with your basement could even be converted into a home office. Or,  if you want to start thinking about expanding your family it would also make a great below-stairs bedroom for one of your loved ones (or a guest-bedroom for visitors, perhaps?)

Cost of Basement Conversion

The cost of a basement conversion (or cellar conversion cost) will vary depending on the size of your property and your exact plans for the chosen area, but to help you budget carefully and get an idea of your average cost of cellar conversions, we have sourced a number of prices for the various stages of work involved in a basement conversion:

  • The main conversion, including digging, plastering and structural renovation will cost between £750 and £1,400 per m²
  • Lower floor level & underpinning  for a basement  will cost between £1,500 and £2,000 per m²
  • Digging new basement space and underpinning a basement will cost between  £2,000 and £3,000 per m²
  • Digging new basement space beneath the garden will cost between  £1,500 and £2,000 per m²
  • Creating light-well/stairwell/remote access entry will cost between £500 and £7,500 per m²
  • Engineer fees will cost between £1,000 and £1,500 per day

In some basement or cellar conversions you may also have to account for the following administrative basement conversion costs too, although planning permission is rarely required if you are only making modest refurbishments or alterations to an existing space. The different costs, which will vary depending on your local council, generally average as the following:

  • A Building Regulations Application will cost on average  £750.00
  • A Planning Permission Application will cost on average  £165.00
  • Party Wall Agreements will cost on average £70.00 per neighbour
  • VAT – if it isn’t already included in the labour fees or contractors/product price guide, you will need to add 20% compulsory taxation to all charges at the end of the bill.

Remember, the first set of basement conversion cost prices are just averages, and for the most specific and up-to-date information you should always compare quotes from a number of different local basement conversion contractors to make sure you get the best deal possible. You should also take into account any additional jobs that may need paying for as a direct result of your upcoming basement conversion – will drains need diverting, for instance, or the house draught-proofing? Will you need additional central heating and lighting installed? Or even a new boiler?

All these things will need to be included in your budget if necessary. Finally, check administrative costs with your local council too, and be 100% certain your project is allowed to proceed before getting started. After all, you don’t want to end up with a half-dug basement conversion spoiling your property, especially during the winter! As long as you plan carefully and take all these factors into consideration, your new basement or cellar conversion should be a smooth and cost-effective investment that’ll be ready in a matter of weeks.

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