The minimum height from the top of the ceiling joist to the bottom of the ridge board should be 2.4m. This will allow you to extend your living area into your previously unused attic.
If the above height is available, you may have the choice of a number of different types of loft conversion and all depends on the structure of your house, planning permission, building regulations and restrictions in your area.
If your attic space is less than 2.4m high and you wish to maximise its utility area, it can be done. There will be less options available, but the transformation of your attic can still become reality.
Feel free to call Unbeatable Builders to discuss your preferred individual requirements.