Can flooring contractors install that before laying the new flooring, or do I need another contractor to do that first?
Depending on where you live and what type of radiant floor heating you want, Either HVAC or Electrical Contractors are able to do this type of work.
Plumbers, and contractors specializing in hydronic heating or radiant heating. General contractors can install the tubing on the underside or topside of the subfloor. Typically a radiant heating contractor will have to hook up the manifold and associated radiant heating mechanical equipment.