Question
I have a 30 year old Sweet Gum in my courtyard.  The garage and house are 8 and 15 feet away, respectively.  Is there any danger that the root system could damage the foundations?

Answer
If the tree is 30+ years old, I doubt it will cause you a problem, if it hasn't already...Here is a website with more info:

http://www.ces.ncsu.edu/depts/hort/consumer/factsheets/trees-new/text/problem_ro...

I have a neighbor's Sycamore (cousin to the Sweet Gum) that is tearing up our backyard patio slab something awful!!  

You can (but do not have to) root-prune the Sweet Gum now to avoid future problems - just trench down about two to three feet parallel to the area that you want to protect, and about 10 feet from the trunk, cutting any large surface roots that have the potential to harm your garage or house in the future...Asuming you do not have to tear up the concret patio or something to get to it.

Purist tree-folks will be shocked by this advice, but its either the tree or your home;  So now is the time to take care of it, rather than after repairing the damage.  ~M

(PS - thanks for waiting for the reply, I forgot to set my "vacation" button at the website this last week)