How do you build a roof?
Roofs are more complex than they look from the outside. Here are the basic steps to building a roof:

1. Build out the shape of the roof with a wood frame. This is the roof's skeleton.
2. Cover the frame with decking. Decking is the first layer of the roof. It's a thin piece of wood that all the other material will rest on. 
3. Add an underlayment on top of the decking. This is a synthetic barrier that guards against water and fire, and helps the roof maintain its shape if the wood under it expands or contracts.
4. Add flashing around vertical elements on the roof. Flashing is a thin sheet of metal that prevents water from getting into gaps around vertical elements like chimneys and vents.
5. Apply shingles to the roof. Shingles are made of asphalt and they are the outermost layer of a roof. Shingles are the first line of defense in protecting your home, but they can also add color and design elements to your home.