GAF is the largest manufacturer of roofing products in North America and has been in business for 125+ years. One of the many reasons they have become such a long-lasting and reputable company is their commitment to quality, both in their products and those they certify to install their roofing materials. To become a factory-certified contractor for GAF means that the roofing company has went through training and certification to meet the GAF stringent set of standards. This investigative look at GAF shingles is for homeowners who are considering GAF products and want to do their due diligence before making the roofing material decision.