Slate as a roofing material goes back centuries. Initially, slate was seen as a ready-made building material, safe against insect infestation and fire. Today, slate has the same qualities, except it also has a cachet or mystique not held by other types of roofing products.
Slate roofing even has such an appeal that replica slate roofing made of rubber and other synthetic products is sometimes used. While slate roofing is frequently seen on homes in Great Britain, it is seen on fewer residences in the U.S.
In the U.S., most of the historic slate-roofed residences tend to be found along the Eastern Seaboard, though newer slate roofs can be found in California, Texas, and Floria.
What Slate Shingle Roofing Is
True slate roof shingles are 100-percent natural stone with no additives. Much like natural granite counters, slate roofing is quarried directly from the earth.
Slate can be identified by the way the light hits it from a certain angle. This is due to slate tile's high mica content. Some slate can have up to 40-percent mica content. So, not only is it the texture of the stone that creates its unique look—it's that low-level shine, as well.
One reason for slate's superior roof-tiling quality is its cleavage abilities. Think of a good piece of slate much like a deck of cards. Because slate is a sedimentary rock, it is formed of many layers, and these layers can cleave, or slice, off like the individual cards in a deck of cards.
Slate shingle roofing requires installers who are experts at working with slate. Because of this, not all areas have companies that can install slate shingle roofing.
Slate Shingle Roofing Through the Centuries
Slate was—and still is, to some degree—a highly desirable roofing material. Advertisements for homes in early 1800s United States boast of domestic slate "machine dressed, and equal in quality, durablity, and appearance to Imported Slate." A New York home in 1829 was sold in glowing terms with a "slate roof excellently and substantially built."
Slate as a popular building material peaked around 1976 to 1977. Slate roofs were still most popular in a few of the obvious places, like Pennsylvania, Ohio, New York, and New Jersey, but they had also migrated to a few of the less-obvious places: California, Texas, and Florida.
By the 1980s, the hundreds of slate-producing quarries in the U.S. had narrowed to just a few in New York, Pennsylvania, Vermont, and Virginia.
Today, slate for roofing comes from a few sources in the U.S. but mainly from China and Brazil.
Slate Roof Pros and Cons
Good resale value
Prone to cracking
Difficult to walk on
Slate roof shingles are aesthetically pleasing. For the right type of classic home style, slate shingles tie in well with the rest of the house.
Durability also is one of slate shingles' strongest points. If undisturbed, the slate material itself can last for 50 or 100 years.
Slate is impervious to insects such as termites or carpenter ants. Because slate is a dense stone, it absorbs relatively little water. Excessive water is one of the causes of rot in a house. If the slate shingle roof is installed well, water will shed away.
As a stone, slate is fireproof. This alone does not protect a home from burning since the deck below and all side elements are susceptible. But it does protect a home from burning due to sparks or embers landing on the roof.
The high cost of the slate materials, plus the installation charges, make slate shingles a difficult purchase for some homeowners. Costs for installed slate roofs vary. In some cases, slate roofing costs between $1,000 to $2,000 or more per square installed (a square is a roofing industry term for 100 square feet).
Few roofing materials weigh more than slate shingles. Conventional composite shingles weigh between 200 and 250 pounds per square. A square of slate shingles can weigh up to four times more: 800 to 1,000 pounds per square. The added cost of shoring up the roof to accept slate shingles can often be a deal-breaker.
Though maintenance needs are reduced with slate shingles, when maintenance is required it can be expensive. Homeowners can find it difficult to repair slate shingles, so professional services are required.
Should You Install a Slate Shingle Roof?
Slate shingle roofing will last for a long time. If you plan to be in your house for at least 30 years, a slate roof may be right for you since the cost will amortize over that long period. For shorter periods of ownership, slate shingles may cost more than their eventual resale value.
If it's simply the look of slate roofing that you want, investigate recycled rubber slate-style shingles. Made from up to 80-percent old tires and other post-consumer rubber products, rubber slate roofing is one of the eco-friendlier products you can use. Rubber slate has the textured look of slate and even its thickness, without many of the downsides of real slate.
Rubber slate roofing is lighter in weight than real slate. While recycled rubber slate shingles are not fireproof, they are considered to be fire-resistant. Natural slate can crack; rubber slate shingles are very flexible and rarely will split.