I declared the future tableViewHeader with this
UIView * ivHeaderContainer = [[UIView alloc]initWithFrame:CGRectMake(0,0,.01,.01)];
Instead of
UIView * ivHeaderContainer = [[UIView alloc]init];
Problem is magically solved. It follows solutions here: Why is there extra padding at the top of my UITableView with style UITableViewStyleGrouped in iOS7
Next question. Why?