When to add a new table or new column I have looked at previous questions dealing with New table or new column and When should I use a new table? and a few others. I'm a little confused, not sure if my problem has a different need/solution; so here goes: 
I have a table for users with a userid, name, email, etc.  This is used for both employees and for customers (at around 800 entries, it is split nearly 50-50).
I have a need to incorporate about 4-6 more columns for just the employees; such as manager, citizenship, office, etc.  These would only be used for the employees and not for the customers.
My question is: do I create another table for the employees with those extra columns or do I add those columns to the 'users' table and default to NULL (for customers) in each one?
I thought this was a different situation than the other questions, which is why I posted it.  If not, please let me know.
Thank you
For proper normalization, I would split them up into two tables. It makes for a more logical design, and easier to maintain down the line if you want to make additional modifications.