File Permissions for multiple users

[psharp]

Hi!
I'm doing some volunteer IT work for a non-profit trying to gain some experience. For the most part things have gone well, however, someone came to me with a question I haven't been able to solve. we have a 21tb raid set up via thunderbolt to a mac mini server. There's about 10 users who have access to the server who typically work on projects together(video/audio team). The person in charge wanted it set up so all 10 users could write to the same drive, rather than partition it into individual blocks; a Pool type mechanic. I however have run into the problem that if a user creates a new directory permissions on that folder are such that said user has read/write assess, and the group "staff"(everyone in the office) has read only access.

At present I'm able to manually set directory permission for staff to have read/write and if I go to the root directory I can apply it to everyone, however once a new folder is created that process has to be repeated.

I would like so that any new directory is initialized with the permissions of the root folder. Is that possible. If so how/where could I find instructions to do it.
Thanks a bunch!