Why not add space in the roof?

If you are wanting to add space to your home an good solution is to convert your loft. 

Where the pitch and head height don't allow for a full conversion to create a useable extra bedroom or study for example the loft can be carefully transformed into useable storage space to free up valuable space in the rest of the house.

A head height of a minimum 2.2m is usable, dormers can be installed to increase the usable floor area and allow light into the new room.

You will need to strengthen the joists to take the weight of people and furniture and you will also need to think where and how you will get a staircase to climb up to the new loft room.

If the ceiling height in the room below is high you may be able to lower the ceiling height to give the loft conversion more head room.

The most expensive way to convert your loft is to completely redeisgn, remove and rebuild the roof structure and will require planning permission.