A roofer, roof mechanic, or roofing contractor is a tradesperson who specializes in roof construction. Roofers replace, repair, and install the roofs of buildings, using a variety of materials, including shingles, bitumen, and metal. Roofing work can be physically demanding because it involves heavy lifting, as well as climbing, bending, and kneeling, often in extreme weather conditions. Curled or rotten shingles, missing shingles, and blistering are all signs that roof needs attention.