The space in a loft or attic can be typically 30% of the total floor area of your home. In almost all cases it is wasted space that can be turned into living space. If the attic is used for storage there is no need to lose all of this storage space as some attic space can be retained.
Loft conversion or roof conversion is often cheaper than extending your home outwards and potentially increase the value of your property by 10% to 20%. In addition you often do not need planning permission for a loft conversion or basement conversion. It may be possible to complete the work without removing the existing roof covering or making any major structural alterations.