When arriving at a total project cost it is important to understand the difference between Construction Cost and Project Cost. Construction Cost is the amount paid to a contractor (typically a General Contractor) for construction of your project. Construction Cost includes the contractor’s overhead and profit (in Seattle and surrounding regions this typically is 12%-20%).
Project Cost includes Construction Cost plus sales tax, permit fees, and fees of design professionals. Typically, the above items add 20%-25% to your Construction Cost. When estimating total project cost, you may also want to include the cost of the land and utility connections (if applicable) and the cost of owner furnished items such as equipment, furnishings and any other items necessary for the project to be used for its intended purpose.
For more information on calculating construction and design costs, see our article on Construction and Design Cost Estimating.