Collocations for contractor - noun

independent, private
external (esp. BrE), outside
government
prime
The prime contractor can take on several subcontractors.

approved
a list of approved contractors

haulage (BrE)
building, concrete (AmE), demolition, electrical, engineering (esp. BrE), masonry (AmE), roofing
civilian, defence/defense, military

employ, hire, select, use
We'll need to employ a building contractor to do the work.