Final answer:
Slate/concrete tile is the heaviest roof material per square foot, with its weight ranging significantly depending on the exact material and style. Other materials like asphalt, fiberglass, and tar & gravel with ballast are considerably lighter.
Step-by-step explanation:
The heaviest roof material per square foot is a. Slate/concrete tile. Slate is a dense, natural stone that is used for high-end roofing. Its weight can range from about 800 to 1,500 pounds per square (100 square feet), making it one of the heaviest roofing materials available. Concrete tiles are also quite heavy, typically ranging from 950 to 1,200 pounds per square.Comparatively, asphalt shingles (b. Asphalt) are much lighter, with weights ranging from approximately 275 to 425 pounds per square. Fiberglass (c. Fiberglass) used in roofing is even lighter and is often integrated into asphalt shingles to reinforce them. Tar and gravel roofs with ballast (d. Tar & gravel with ballast), although substantial, tend to be lighter than slate/concrete tile. The weight of a tar and gravel roof can vary but generally includes the weight of the tar layer, the waterproof membrane, and the gravel ballast, and ranges between 400 to 575 pounds per square.In conclusion, when considering the heaviest roofing material per square foot, slate and concrete tiles are the heaviest options and should be used only in structures that can support their weight.