This is some info from a cl***:::
http://www.intlcodeconsultants.com/North%20Texas%20ICC%20Chapter%20Talk%20on%202009%20Ht.%20&%20Area%20v2.pdf
http://www.intlcodeconsultants.com/North%20Texas%20ICC%20Chapter%20Talk%20on%202009%20Ht.%20&%20Area%20v2.pdf