Great Lakes Construction
3413 47th Ave.
Kenosha WI 53144

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Slate Roofing


slaterofoSlate is a fine-grained, foliated, homogeneous metamorphic rock derived from an original shale-type sedimentary rock composed of clay or volcanic ash through low-grade regional metamorphism.


Not all slate roofing materials are the same. There is a grading system used to determine the quality of the material. S-1 means the slate will last more than 75 years. S-2 slate is meant to last 45 to 75 years and S-3 slates are meant to last 45 years or less. However, slates of all three grades generally do last longer than their required minimums and last much longer than cedar shakes or asphalt shingles.


Slate roofing can come in a variety of colors from gray, green, purple, black, and red. Sometimes there is a mottling effect, mixing a couple of these colors together, the most common being gray-black, gray-green, and green-purple.

Slate roofing can weather. Sometimes, green and gray slates can develop brownish and pinkish tints, due to iron in the slate. At the time of new installation, the percentage that will turn color is unpredictable. It can be as little as 5 to 10 percent or nearly 100%. The only way to predict for certain what a roof will look like (if one wishes to have a weathering slate) is to install a reclaimed slate which has already undergone the weathering process.


How much does slate roofing cost?


Slate roofing is generally the most expensive roofing material over cedar and asphalt roofing. Because there is less demand for slate roofing material and the cost of mining, slate roofs will run you more money upfront. However, the investment could literally last you a lifetime and more.


How long does a slate roof last?


As mentioned above, slate roofs can last from 45 years up to more than 75. There are some slate roofs in Europe that are hundreds of years old.