Having a new roof put on a building is sometimes necessary to help keep the interior of the structure protected from the weather. Failing to get it done properly and in a timely fashion can mean that the inside of the building suffers damage. This can be costly.
Building contractors have a lot of responsibility to the people who hire them. They need to make sure that they understand the project, have the skills to do the work and can get the proper supplies for the job. Most of the time, they do what they have to do and the client is satisfied upon completion of the project. In the other cases, if some facet of the project didn't go as it should, there can be disagreements about how to resolve the matter.