From the VA DMV web site.

http://www.dmv.virginia.gov/webdoc/pdf/dmv109.pdf

Operators of vehicles having a manufacturer’s
gross vehicle weight rating (GVWR) or a gross
combination weight rating (GCWR) of 26,001
lbs. or more are required to hold a valid CDL.
Operators of vehicles designed to carry 16 or
more persons including the driver, and operators
of vehicles hauling hazardous materials which
are required by federal law to be placarded must
also hold a valid CDL.

The following situations exempt operators of certain vehicles from the CDL requirements.
1. Operation of a vehicle for personal use only,
such as a recreational vehicle or truck to move
your personal belongings.
2. Operation of a fire truck or other emerency
vehicle.
3. Operation of a farm vehicle that meets all of
the following conditions:
a. Controlled and operated by a farmer.
b. Used to transport agricultural products,
farm machinery or farm supplies to and
from a farm.
c. Strictly for farm use and not used in the
operation of a common contract
carrier.
d. Used within 150 miles of the vehicle
owner’s farm.
4. Operation of a vehicle for military purposes
while the operator is on active duty carrier.