It varies by school. The 529 spending for room and board is only considered qualified if it is not more than the higher of either:
-The allowance for room and board, as determined by the eligible educational institution, that was included in the cost of attendance (for federal financial aid purposes) for a particular academic period and living arrangement of the student.
or
-The actual amount charged if the student is residing in housing owned or operated by the eligible educational institution.
So if the school’s allowance for off-campus room and board is $12k, and the student living off campus takes $13k in 529 distributions to pay rent and buy food, there will be $1k in non-qualified 529 distributions where the earnings portion will be subject to income tax and the additional 10% penalty.