In a new construction, the builder laid the cement floor as one piece. Later, for reasons unknown, he dug up the half of the finished floor from the center of the garage to the garage door. Laid new cement with an expansion joint from the original cement to the door. Now there is a down slope on the new cement towards the door and a noticeably 1/2 inch step up to the original cement. I would like to have some argument point to present my case to re-do the whole over as one piece before a final walk through of the home. thank you
Sorry for being so slow!
I cannot find anything in the International Residential Code. However, in Texas our warranty standards say the 1/2" difference you have would be unacceptable as 1/4" is the max. The only other number is a 3/8" drop over a 32" horizontal distance is allowed.
In addition, I think it would be a good idea to hire an independent home inspector that specializes in new construction to inspect your house.