A contractor or residential designer helps you coordinate your job and determine who will be needed to perform specific duties. A contractor looks at the total job; determines labor, material and time needs; draws up a cost estimate; and hires the workers. A contractor can take the hassle out of a large job for you since he is the one with whom you'll be dealing directly. Without a contractor, you'll have to hire individual specialty workers - like carpenters, electricians, cement masons or plumbers - to complete each part of the project. A contractor often has a degree in a construction management field. Many have extensive experience working in the construction field and after years on the job have moved into general contracting. Some will perform double duty by planning the job, but then also performing some of the work. Contractors and cost estimators often have certification from a professional organization. Contractors have to be knowledgeable in the full range of construction specialties, as well as community zoning and permit