How to Calculate the Cost of a Room Addition

Call your city's building or zoning department to inquire about costs of building permits, including any fees and application costs.

Measure how big your addition will be. The cost of your addition will vary according to how many square feet you are adding. An easy way to figure your dimensions is to use spray paint or chalk to outline where your addition will go. This will help you to visualize any obstacles, like a tree, that you may have to work around. This information will also be necessary when you ask for quotes from a contractor.

Call contractors and ask about typical labor rates. This will give you a rough idea of what the contractor would charge for the labor portion of this job. Call plumbers, electricians and any other type of contractor you may need to complete the addition.

Create an itemized list of everything you will need for your addition. This includes, but is not limited to, a foundation if you need one, drywall, wood for framing, carpet and any appliances that you want in your addition.

Calculate the total of all the expenses together to determine what your total cost will be. It would be very prudent to add an additional 10 to 15 percent for unforeseen costs.