Converting an existing cellar into a liveable area can be a cost effective way to add space to your home; especially if you are unable to expand into the loft or build an extension. Building a whole new basement can be an expensive and disruptive endeavour and you will be required to have planning permission. While converting an existing cellar may not require planning permission, usually takes less time and can be cheaper. 

How much does it cost of covert an existing cellar?

According to Real Homes Magazine, a ballpark price of turning existing basement space into a habitable space can cost between £720-£1,800 per square metre. A brand new basement can cost in the region of £1,920-£2,640 per square metre. Of course, these prices are not set in stone, as it depends on the size of your cellar and what you plan on using your basement for. For example, a swimming pool will cost much more than a play room.

Do you need planning permission to convert an existing cellar?

It is unlikely that you will require planning permission to convert an existing cellar into a liveable space. However, it is always advisable to check with your local authority before starting any work. At Simply Basement, we will help guide you through the planning permission process should you need it.

If you plan on converting your basement into a separate property then you will have to seek planning permission. Properties that are situated in conservation areas may need planning permission, especially if you are altering the façade of the house. Again, always check with your local authority.

Building regulations

If you are converting an existing cellar you will have to meet certain building regulations for it to be legally habitable. These regulations include:

  • Achieving sufficient levels of insulation
  • Creating an emergency escape route
  • Having a minimum ceiling height: many Victorian basements do not always meet this, which means you’ll have to lower the floor
  • Ensuring the right structural supports are in place: if any structural work is carried out it will have to be signed off by a building inspector

When budgeting for your cellar conversion you need to take into account the cost of building regulation applications. The cost will depend on the work and what your local council charges. More information on building regulation applications can be found here.

If you’re converting an existing cellar will you need to get a party wall agreement?

If you live in a detached house you may not have to get a party wall agreement. However, if you share a wall with your neighbour(s) then you will have to get each of your neighbour’s consent in writing before work commences. The Party Wall etc. Act 1996, lays out in law a framework for resolving or preventing disputes in relation to a party, boundary wall or excavations near neighbouring buildings.

To make sure you keep the neighbours onside, speak to them about your plans and listen to their concerns. To ensure minimal complications the correct notices will need to be sent and consent obtained in writing. Click for more information on keeping good relationships with your neighbours.

Waterproofing your cellar

One of the most important jobs that need to be carried out when you are converting an existing cellar space is the waterproofing or tanking of your basement. Basements are naturally damp places, so ensuring damp does not become a problem, some form of waterproofing needs to take place. Tanking is the most common way of waterproofing a subterranean space. The practice can include coating the interior wall with a form of watertight membrane, render or sealant. At Simply Basement, we can advise on the best way of keeping your basement damp free depending on your situation.

Want to gain more space in your London home by converting your existing cellar space? Then contact Simply Basement for a free site survey.


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