A two storey extension adds additional space throughout a house, usually adding considerable value as well. The extension may be to the front, side or rear, perhaps taking the form of a gable addition or visually widening the dwelling.
Many houses have an attached garage, with the possibility of a room being constructed above, or an extension to the side that incorporates a garage, plus a room above. It is possible to construct a single storey extension with the aim of a further first floor extension above at later date.
A bungalow can be converted into a full two storey dwelling, or a one and a half storey, with the first floor being partially in the roof space.
Design consideration must also be given to the internal alterations that will be required to access the new spaces, as this is vitally important to maximise the usage and added value.