Basement/Cellar Conversions

Converting a cellar or basement into a living area can be a cost efficient way to add more space into your home; it can be a viable alternative if you aren’t able to expand into the loft or build a new extension onto your property. Converting an existing basement or cellar is usually quicker and often cheaper.

Is planning permission required?

This really depends on the scale of changes you are going to make. You are unlikely to need planning permission for converting an existing cellar into a liveable area, but if the changes you make reflect the exterior of your property, planning permission might be mandatory. But be sure to check with your local authority first before starting any work. If you want to know more about Planning Permission and the process, check out our recent blog covering it.

How much will it cost?

According to figures touted by Real Homes magazine, an estimated price of converting an existing basement or cellar space into a liveable area can cost between £720 – £,1800 (per sq. metre), yet for an entirely new basement or cellar space between £1,920 - £2,640 (per sq. metre).

The prices above are rough estimates, as it will depend on how big your space is and your plans for it; installing a new gym will probably cost more than a play room.

Building regulations

When converting an existing basement or cellar, you’ll be required to meet various building regulations for it to legally viable, including:

  • Implementing an emergency escape route
  • Implementing the correct structural supports: whatever structural work is carried out will need to be approved by a building inspector
  • Meeting the minimum levels of insulation

When calculating the budget for your conversion, don’t forget to include the cost of building regulation applications. How much it costs will depend on the work itself as well as what your local council will charge.


Another vital job that must be carried out when converting a basement or cellar is the waterproofing of it. Underground spaces such as these are damp areas, so you need to ensure this doesn’t become an issue.

Are you considering giving your basement or cellar a makeover? Let us know on Twitter @haart_uk!