If you are planning on making any template changes (eg: changing code in files such as the header.php and other templates), then you should consider doing so using WordPress Child Themes.
A child theme is basically a copy of the parent theme file, so instead of changing the theme files of the parent (foundation) theme, you make changes to the child theme. This prevents any theme update from overriding any changes you made, and it’s also good practice to leave the parent theme file intact, that way, if anything goes wrong with your code, you have only messed with the child theme and the parent remains in its original state.
Any changes made to the parent template files will be overwritten when you update your theme and unless you have a backup, you wont be able to get those changes back.
If you need help creating a child theme, you can use this handy plugin and guide.