Slate Roofing and Slate Roof Repair
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Slate roof tiles are made from slate, a naturally occurring stone. Slate comes in gray, green, purple, black or red; you can also find variegated slate that blends these colors. Slate is composed of clay and mud that solidify over time into quartz, mica and chlorite.
Roofing slates comes with a grade that indicates how long it will last. According to Durable Slate, a grade of S-1 means a life expectancy of 75 years or longer. S-2 slate lasts 45 to 75 years and S-3 slate will last up to 45 years. As Durable Slate notes, many slates outlast the time frame on their grade.
During installation, slate shingles traditionally get pounded into your roof with nails. Since slate cannot be bent, most slate roofs have steel or copper flashing that cover these corners and odd angles. Ask the Builder notes that a new technique allows slate roofing to be installed on a track, meaning that you don't need to use nails.
Slate's downfall is the naturally brittle nature of the stone. If you drive the nail to deep (or too shallow) during installation, the slate shingle can crack and fall off your roof. While your slate roof won't need much maintenance, shingles can crack when people climb on your roof to clean your gutters or chimney. Freezing cold cycles also may cause slate shingles to crack.
Slate Roof Repair - Signs of Problems
Odds are the slate on a roof is old. The material was most commonly used in the early 1900s. Check the slate with a screwdriver. If it is soft or flakes off when probed then it is failing. Slate in good condition is hard. Don't probe the slate roof tile too hard. If it is in good condition it is as brittle as glass. Check for loose slate while inspecting the tile.
Sometimes the slate itself is not the problem. Moisture causes swelling of the roof boards, which may cause the roofing nails to work loose. If copper nails and flashing were used during the slate installation this problem is minimized.
While very durable slate roofing tile do occasionally break. Removing the broken slate usually isn't difficult because the pieces are loose. Use a slate ripper hook to remove the nails that held broken slate in place. Replace the slate nailing it is place through the gap between the next course of slate.
Preventing Slate Roof Problems
Slate roofs should dry as quickly as possible after any rain event. This prevents moisture accumulation under the slate. Trim any trees close to the home so that the roof is not shaded. Allow the sunlight to dry the roof as quickly as possible.