Calgary Roofing Company PDQ Roofing since 1956. Residential New Roofing, Re-Roofing, and Repairs. Call for a free roofing quote. As a professional company we maintain our COR certification. COR is recognized by Occupational Health and Safety as well as the Worker's Compensation Board as a necessary method of operation to insure that all of our workers working at your property have received the required safety training and certification. We perform both internal and external audits on a regular basis so that we can participate in these government programs.