Cost to Build a Home-Square Foot Estimates

Hi Carl. Thanks for you book and for the great website. I've had the book for a while but just got to the website.I have a couple of questions about square footage cost...maybe you can help. In your book you talk about adding up the heated space to come up with your square footage. So just to be clear, when I see a plan for say, 2000sq ft on the internet, the cost of the garage is just