Doing a loft conversion is the best solution when the area around your home is small and you do not want to do a house extension at the cost of reducing hthe garden. Loft conversion is also better from an economic point of view. If the walls are solid and in good condition, loft conversion is usually quite simple, and its cost can be contained in the cost of a roof renovation. When the roof needs repair, maybe a better solution is to build a new floor rather than just doing a roof renovation. Because loft conversion also means more space in your home.
Doing a loft conversion is also usually cheaper as we avoid costly ground works. We do not need to change the foundations, we do not violate the insulation in the ground and we also do not need to disturb the garden. However, a loft conversion requires the construction of stairs.
Adding new stairs in to an old house is associated with functional and structural changes. You will have to order a project from an architect. You will then have to knock a hole in the floor above the ground floor.