Server Side includes with Multiple Folders


I want to try using SSIs and am designing a site that has multiple folders containing various pages (relating to each section of the site).

How do i get SSI to work so that i can display a footer include on every page on the entire site?

Problem seems to be that the includes path is relative, but i need absolute and the server doesn’t like this? i assume the includes can be stored in the site root?

EG; includes folder to display includes to the - projects folder pages, healthcare folder pages, retail folder pages - so that the same footer is located on every page.