Often customers ask us, “What is a GAF certified roofer?” GAF roofing products are America’s top-selling roofing shingle brand. And GAF certified installers know the correct way to install these great products on your home. GAF products installed by a GAF certified installer get you the most out of your roofing warranty, including a lifetime warranty on the shingles and 25 years on workmanship on GAF select products.