Some roof spaces are more easily converted than others and a full assessment requires professional help. But the untrained eye can often work out the basics.
The Minimum Ceiling Height
The size and shape of the existing roof space will determine whether it can be used for living accommodation.
A ceiling height of 2.3 metres is the preferred minimum for habitable rooms, i.e., rooms other than bathrooms and kitchens. This height need not be maintained over the whole floor area and the usable floor space of rooms can be based upon the height needed for standing and walking or accommodating furniture.
Lower room heights may be acceptable for bathrooms, corridors, kitchens or storage. A minimum ceiling height however is requires at the head of the stairs to comply to regulations/ standards.
What You Can Do?
Go up into your loft and take a look around. Is there enough headroom at the centre under the ridge? You ideally need 8ft (2.4m) clearance, although you may find that you can still get a useful room from as little as 7ft. A quick check with a tape measure will suffice.
Space For Access And Fire Escape
The conversion of a roof space into habitable accommodation must include provision for safe access and exit. This requires a fixed staircase which should comply with the requirements of the building regulations and standards in respect of its pitch, headroom, stair width and balustrading and for safe access, normally on emergency exit.