I am planning on pouring a 14' by 24' concrete patio at the level of the walkout basement sliding door. The original grading of the house sloped from part way up the poured concrete foundation wall down about 22" to the small 2' by 6' patio at the door. After excavating this area I found the footing of the house about 3" below the level of the doorway. The county inspector suggested that part of the footing might not be a 'frost' footing as it was expected to be underground and might only go down 8". He suggested that I use insulation under the concrete patio to prevent frost heave. A contractor suggested that the footer should go down 24" and that I should not worry about it. This is scary - any thoughts about what I should do?

Find out what the frost line is where you live, the contractors will fudge a little if we fill its not that big of a deal, inspectors will just tell you the code,
If you were to pour a 24" footing I can't imagine that going anywhere.