Properly installed natural slate roofing has timeless durability in Portola Valley, California. And it doesn't require much maintenance, although a cracked tile or two in a natural slate roof might have to be repaired or replaced.

Natural slate roofing comes in gray, purple, green and red. It is available in two types: premium clear pieces and ribbon slate. Ribbon slate is not as durable as the premium clear product. It is distinguished by the ribbons of light color that run across its surface. The ribbons are high-carbon-content areas. They are an impurity in the slate and are weaker than the dark areas.

If you are going to spend money on roof replacement, spend a little more on natural slate, and get the best.