Converting an existing cellar or basement into living accommodation can be an option for those who want a larger home but without the cost of moving. Money is probably better put into actual bricks and mortar than it is into stamp duty, legal fees, estate agency and removal costs!!
A basement conversion can add significantly to the value of your home, and can often be created without the need for extensive building works. Older property can be particularly well suited to a basement conversion because of the use of ''suspended'' timber floors, which can be modified much more easily than modern concrete alternatives. And most of the work can be undertaken without disturbing you in the main body of the house.
Unless you are in a conservation area, you have a listed property, you are enlarging the footprint of the property, or you are simultaneously changing the use of the property, Planning Permission will not normally be required, although you will still have to comply with Building Regulations. These are primarily designed for health and safety reasons to ensure that you provide adequate fire escape routes, damp proofing, ventilation, electrical and water supply and drainage access.
If you intend doing work to a terraced, or end of terrace house, you will probably also need to consider next door's interests and establish a Party Wall Agreement so that any changes to next door's walls are accounted for.
Damp is the obvious issue in converting a cellar and tanking (waterproofing) a room can be expensive. Bear in mind that changes in humidity can sometimes affect other parts of the house, especially the ground floor timbers, which could shrink or expand. Adequate permanent ventilation is vital. Air bricks may be sufficient for this purpose, but extractor fans may be necessary in some cases. Good heating obviously helps, and it may be that your existing boiler is powerful enough to cope with additional radiators downstairs.
And if you are thinking of excavating a cellar that does not already exist-DON'T!