The most common method for compensating the contractor, allowing for changes to the scope of work during the construction period, is called:

Lump sum contract.

Explanation:

A contractor can be defined as an individual who is saddled with the responsibility of overseeing, supervising, monitoring, controlling and analyzing the construction process of a project or property.

A contract can be defined as an agreement between two or more parties (group of people) which gives rise to a mutual legal obligation or enforceable by law. There are various types of contracts used in field of construction and one of such is a lump-sum contract.

A lump sum contract is also known as stipulated sum and it refers to a type of contract in which a contractor states a predetermined amount of money (single price) that would be used to execute and complete a particular project.

Hence, the most common method for compensating the contractor, allowing for changes to the scope of work during the construction period, is called lump sum contract.