Slate Roof Review: Pros, Cons, and Costs

Extremely durable and possessing natural beauty, a slate roof has long represented the highest standard of roofing materials. Slate is nearly permanent. When a slate roof is well maintained, it can last up to a century or two. As a natural stone, slate can resist decades of weather with no decay, while preserving the rest of the home. Synthetic slate roofing should be considered along with natural slate. Synthetic slate offers a similar look yet it has cost and installation benefits not found in natural slate.

What Is Slate Roofing?

Slate roof shingles are made from natural stone quarried directly from the earth. One of the oldest types of roofing tiles, slate tiles are durable, waterproof, and insect-proof. Like terra-cotta or metal roofing, slate roofing is made entirely from inorganic materials, so the shingles never rot or decay.

Most slate shingles for homes are either random-width or constant-width. Random-width shingles contribute to a more natural, informal look and come in at least two different widths. Constant-width slate shingles give the roof a more formal, uniform look and use one width for all of the roof. Slate is also one of the most expensive roofing products on the market.

Important Slate Roofing Features

Longevity

No other roofing material lasts as long as slate. The life expectancy of a slate roof is anywhere from 50 to 200 years.

To compare, asphalt rolled roofing, appropriate for sheds and outbuildings, may last up to a decade. Composite shingle roofing, the most common residential roofing material, may last up to 30 or 40 years. Only clay or cement roofing approaches slate's longevity, with expected lifespans of up to 100 years.

Appearance

A slate roof's unique sheen comes from the high level of mica in the stone. This brilliant mineral makes slate glisten when viewed from certain angles.

Slate's other distinguishing feature is its rough-hewn appearance. Because slate is a sedimentary rock, it is formed of many layers that cleave, or slice, like the individual cards in a deck of cards. One style of slate called textural slate has uneven thicknesses of shingles with rounded edges.

Hardness

There are two types of natural slate for roofs: hard or soft slate. Hard slate is denser, stronger, lasts longer, comes in varied colors, and is typically the choice for most roofs. Soft slate has a slightly different composition making it less dense than hard slate but it is still strong and durable. Soft slate lasts half as long as hard slate, usually comes in black only, and is less expensive than hard slate.

Environmental Qualities

Longevity contributes to slate's environmental qualities. Slate can outlive several cycles of composite roofing. On average, composite shingles need to be removed and replaced every 25 to 30 years.

As a petroleum-based product, composite shingles are largely sent to the landfill, with only a few being recycled. Slate shingles in good condition can be reused as shingles or can be ground up and used for other applications.

Weight

Slate weighs two to three times more than composite shingles. Conventional three-tab composite shingles weigh around 250 pounds per square (per 100 square feet), with some premium architectural-grade composite shingles weighing around 450 pounds per square. Most homes' roof systems are designed to carry that weight.

By contrast, natural slate shingles weigh between 675 and 1,870 pounds per 100 square feet, a weight that some roofing systems cannot bear. It's important to consult with a qualified contractor or structural engineer before slating a home.

Slate Roof Costs

*Hard slate costs

As with any other premium roofing product, slate roofing costs are steep. Expect to pay a minimum of $1,000 to $3,000 per roofing square, averaging $1,500 a square, depending on where the home is located, the roof configuration including roof pitch, and the size of the home.

Maintenance and Repair

While slate is very hard, it is also brittle, meaning it can crack upon sharp impact. Falling tree limbs that may only dent composite shingles will crack slate shingles.

Qualified professionals are best suited to handle slate roof repairs. Slate is difficult to walk on because it can be damaged and it's slippery so there's a risk of falling. A support system is necessary when working on a slate roof.

In addition, slate roof repairs are difficult because the material has so many variations. It can be difficult to source and blend matching replacements for this natural product. 

Slate Roof Design and Styles

Textural Slate Roof

A textural slate roof has the look of the classic slate roof, with a rough, textured, and natural appearance. The texture enhances the depth and visual interest of the shingles. Though most slate is difficult to walk on, a textural slate provides the best grip of any slate surface.

Standard Slate Roof

A standard slate roof has the opposite appearance of a textural slate roof. The shingles are flat, smooth, and uniform in color and appearance. The clean, elegant look of standard slate shingles complements modern architecture.

Multicolored (Blended) Slate Roof

Multicolored (blended) slate roofing mixes various colors to create a unique and eye-catching look. Shades of gray, green, black, and purple combine to form a harmonious palette. Multicolored slate roofs have a striking but natural and organic look that enhances most homes.

Slate Roof Installation

Slate roof installation is not a do-it-yourself project. In general, roofing is a project only for the most highly experienced DIYers, and slate installation is a highly specialized subset of roofing that requires certain tools not available to DIYers, such as a slate hammer, ripper, slate cutter, and a punch for creating nail holes.

Slate needs to be properly sorted, culled, and blended to ensure a consistent look and quality across the entire roof. Slate shingle roofing requires installers experienced in working with slate. This means that not all areas have companies that can install slate shingle roofing.

Top Brands of Slate Roof

Most slate roof shingles are sourced from quarries in New York, Pennsylvania, Vermont, and Virginia. A few quarriers sell slate directly, while most sell through distributors. Here's where to start:

• Glendyne, Inc.: Quebec-based quarrier that operates the largest slate quarry in North America
• Newmont Slate Company: Based in Vermont, the largest roofing slate producer in the United States
• New England Slate: Vermont-based distributor of slate shingles, all with 75-year warranties 
• Vermont Slate Company: Georgia-based manufacturer and distributor of around 20 lines of high-quality slate shingles

Natural Slate vs. Synthetic Slate Roofs

Synthetic slate roofing creates the look of slate roofing without the weight, cost, and installation difficulties of natural slate.

Made from up to 80 percent old tires and other post-consumer rubber products, synthetic slate roofing is one of the more eco-friendly products you can use. It has the textured look of slate and even its thickness, without many of the downsides of real slate.

Recycled rubber slate shingles are not fireproof but they are considered to be fire-resistant. Where natural slate shingles tend to crack, slate shingles are very flexible and rarely will split. Synthetic slate shingles are half the cost of natural slate and less than hybrid slate. It is the most affordable slate roof, coming in at about $5 to $10 per square foot.

Is a Slate Roof Right For You?

Homes with a classic but casual look will benefit from a textural slate roof, while contemporary homes or stately older homes are best paired with standard slate. Slate roofs work for homes in temperate or cold climates since slate is not considered a cool roof. 

Because a slate roof costs up to three times that of a conventional composite roof, it's best suited for homeowners who can finance this expensive project. If you expect to remain in the home for over 30 years, though, the high cost of the slate roof will amortize, resulting in a lower per-year cost over the long term.