Addition and alterations works refer to changes made to an existing building structure or design. These changes may include the extension of a room, modification of a floor plan, or even a complete overhaul of the building's design. These works are performed to improve the functionality, aesthetic, or value of a building. A professional contractor will carry out a thorough assessment of the existing building structure before proceeding with the alterations to ensure that the changes are safe and conform to building codes and regulations.