How to Determine the Square Footage of a Home

“Hey Carl... I'm soon to start on my house and have researched your books and they are great! My question is do framing subs go by heated square foot or under roof square foot?

Hi Ryan,
Framing carpenters “go by” (framed) area under roof.

On “Cost Estimating Explained”, as well as in Chapter 3 of my book, you can read the following:
“The best way to contract for this job is by the square foot with the square footage agreed to before you start. Five people will arrive at five different square footage totals, using the same set of plans. Some will vary by 300 square feet or more. Sounds incredible, doesn’t it? But I swear that it’s true.

In determining the square footage, houses are measured from outside wall to outside wall, not from roof overhangs. If the house is not easily divided into rectangles for simplifying square footage determination and you can’t figure it out, have the designer do it for you. Ready-made plans generally come with the square footage broken down for you. Use those figures.”
Carl Heldmann,