I know there would be various factors involved, but just after a ball-park figure. Looking at a house but it is a bit restrictive in size and feels like it needs another living area.

It's a brick house and not sure of its foundations at this stage as we would have to get them checked out. Tile roof. Only looking at making it a rumpus style room at this stage. Not sure if it should go above the garage or main part of house.

Size of it would at least be 5x5m. Would probably look better if it went above main part of the house.