Hello,
Directadmin is designed so that it restarts (or reloads) apache, every time when a new domain is added as well as on some other actions. If in your case apache is not restarted, then you should either investigate the issue and find reasons of such a behavior, or hire somebody to do that for you (I'm as well as others available for this kind of a job).
Did you check directadmin logs? How do you restart apache: in directadmin or in a shell?