How can I setup a shared directory so that files moved/copied into the directory inherit the directory's permissions?

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http://askubuntu.com – There have been several questions regarding the creation of a shared directory accessible to all users of a group (notably this one); however I have yet to find a satisfactory answer to this specific problem. I have a directory (/home/shared) which is owned by root:lab and has 2775 permissions (rwxrwsr-x). The intent of this directory is that all users in group lab can work together on files in the directory. This currently works fine so long as files and directories are created within the /home/shared directory, but requires manual editing of permissions whenever files are copied over from a (HowTos)