Having work done in the construction industry can be a complex undertaking. You have to find a contractor who can get the project done, and you have to find terms that are negotiable to both sides. In most cases, there are going to be adjustments to the terms of the contract when you are working through the project. These alterations are usually relayed through change orders.
A change order is an addition or omission from the original contract. Both parties have to agree on the terms of the order. There are many reasons why this might be necessary. Something as simple as adding a window to a home's plans or deciding that you want a different type of flooring would require a change order.
More serious change orders can come when the final completion date needs to be extended or part of the original plans can't be completed as stated. They are also needed when the price of the job is going to change considerably. For example, if the owner makes changes to the project so they can save money, a change order is necessary.
Most contracts have a cardinal change doctrine that prevents either party from overreaching the changes that can be made. This is typically included as a protection for the contractor so that they aren't forced to deal with massive changes to a project. For example, a contractor who is supposed to add a bathroom onto an existing home wouldn't be expected to add an entire story to the home instead.
People who are hiring contractors should be sure they fully understand the contract they are signing. This ensures they know what they need to do and what the contractor is responsible for doing.