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The Ultimate Guide to Slate Roofing: Options, Costs, and Maintenance

What is slate roofing and why would I want it? Slate roofing is an age-old way to keep homes dry and comfortable. Today, we will discuss what a slate roof is, how long they last, and why you might want one.

Source: Pixabay.com

What Is Slate Roofing?

The term slate roofing refers to using both natural and synthetic slate as a shingle to repel rain and snow. Using slate for construction goes back many centuries because slate has some fantastic properties. Slate is fireproof, so sparks and embers landing on the roof will not ignite, plus it will usually outlive the home it is on.

Slate roofing is made from either natural slate stone or synthetically molded using materials like rubber or resins. Natural slate is considered the most durable roofing material you can buy, but it is extremely heavy and expensive to both purchase and uninstall.

Synthetic slate is less expensive and lighter, but will not last nearly as long as natural slate roofing. A slate roof will likely need a new drip edge, underlayment, and flashing as well.

Why Is Slate a Good Roof Material?

Natural slate roofing can be made from two common forms of slate, hard slate and soft slate. Both are completely natural, but hard slate is more dense than soft slate and is virtually impenetrable by water. Soft slate is usually less expensive than hard slate, but the installation is very similar. 

How Are Slate Roofs Made

Natural slates make great roofing material because slate is a sedimentary rock, meaning it forms in layers, in contrast to river rocks, which tend to be thick. Slate roofing manufacturers harvest the stone and use machinery similar to those used to produce granite countertops. After the slate makes its way to the mill it is split into various sizes and shapes for use as a shingle.

Synthetic slate roofs are created using an entirely different process that attempts to address some of the common downsides to natural slate roofs. For example, synthetic slate roofs can be made from a number of materials, like rubber, resins, or even metal. All of these materials address a shortcoming of natural slate, such as less weight and lower cost.

Synthetic slate roof materials are usually either molded or extruded in a factory setting, which provides for consistent slates. Synthetic slate roofs materials also offer more design choices, like texture, color, and shape, allowing the designer more creative freedom. Many of these materials compete with natural slate in many areas, but none can come close to the lifespan.

Is a Slate Roof Heavy?

A slate roof is very heavy, especially when compared to a traditional asphalt shingle. A natural slate will usually weigh somewhere between three and four times what the same roof would weigh if a fiberglass/asphalt roof were installed. 

The additional weight of a natural slate roof is one reason why they are more expensive to own. The additional structural support required for a natural slate roof can be substantial, leading to additional costs to own.

What Is Under a Slate Roof?

Source: slateroofwarehouse.com

A typical slate roof will incorporate the same support and underlayment as other styles of roofing. Other considerations, like snow guards and ice and water shields, can be used with slate roofing just as they are with fiberglass/asphalt, tile, and other forms of roofing.

 Special attention should always be given to flashing on a slate roof, however, because slate roofs last so long. Flashing should always be made from very long lasting materials like copper and stainless steel to prevent unnecessary repairs.

How Long Does Slate Roof Last

A natural slate roof that is expertly installed and maintained can be inherited by your great- grandchildren. Most natural slate roofs are expected to last at least 75 years, while some can last 200 years.

Obviously, natural slate is very resistant to fire or insect damage, so as long as they are maintained, a slate roof can outlive the home. As long as damaged slates are promptly replaced and water is not allowed to weaken the framing, a natural slate roof can be the only roof a structure ever has.

How Often Does a Slate Roof Need Replacing 

Slate roofs in general, and natural slate roofs in particular, aren’t usually so much replaced as they are repaired. As mentioned earlier, a slate roof is designed to last a very long time, whether it is synthetic or natural slate.

Some homeowners regard a slate roof as a major investment in a home they plan to pass on. Others are using slate as a design element, often on very elaborate personal residences.

How Do You Maintain a Slate Roof

Slate roofing is extremely durable, so the only real maintenance involves inspecting your roof often and looking for signs of wear. Generally, as long as no external damage has occurred, a slate roof will require only periodic cleaning. Removing any debris that would prevent water from shedding is the most important part of the cleaning process.

Can You Pressure Wash a Slate Roof?

Slate roofs can be easily damaged by a pressure washer, so never use one to clean your roof. Slate roofs do need to be cleaned regularly though, to prevent moss build up. Some home owners simply hire a roof cleaning company, but you’ll want to find one with experience cleaning slate. Cleaning a slate roof requires skill and patience, not to mention the lack of a place to stand. 

Slate roofs cannot be walked on because they are quite brittle and can be broken easily. Slate is thin, making it vulnerable to footsteps and other significant weight focused on a single slate. Roof cleaning companies have a number of ways to clean a slate roof, but most involve some form of walk boards to avoid stepping on the slate.

What Are the Most Common Slate Roofing Types

The most common forms of slate roofing are natural slate, rubber, fiberglass, resins, metal, and concrete. Technically, you can also group fiberglass/asphalt shingles into this category, as most dimensional shingles (30 year) are designed to mimic a slate roof appearance.

Natural Slate

Source: Unsplash.com

Natural slate is produced by splitting natural slate stones into shingles. Natural slate is naturally deposited in layers, making it very easy to split into fairly uniform shingles. Natural slate is generally separated into two categories, hard and soft.

Hard slate is more difficult to work with, but is the longest latest roofing material available. Soft slate is typically more malleable, but may only have about half the lifespan of hard slate. However, even soft slate often lasts 75 years or more with proper maintenance. 

Fiber/Cement

Source: cedral.world

Fiber cement slate is molded from fiberglass strands and cement, much like the popular lap siding. Fiber cement slate roofs are available in a wide variety of colors, patterns, and designs to suit essentially any home design. Fiber cement roofs are relatively inexpensive to install compared to other forms of slate roofing, but they require the most maintenance.

Synthetic (Resin)

Source: davinciroofscapes.com

Synthetic slate roofing is a product molded from a mixture of resins and other additives to address common shortcomings of natural slate. Synthetic slate roofing is much lighter, more resistant to impacts, and costs less than natural slate roofing. Most are available in an array of dark grays, dark browns, and black. 

Concrete Slate and Tiles

Source: arcat.com

Concrete slate and tile roofing is an attempt to achieve the look of natural stone or clay, without the cost. Unfortunately, cost is about the only real advantage to a concrete roof because it retains or worsens most of the complaints concerning natural stone.

Concrete slate roofs require constant maintenance, are susceptible to both moisture damage and impact damage, and are just as heavy (if not heavier) than a natural slate roof.

Rubber Slate and Tiles

Source: greenspec.co.uk

Rubber slate roofing tiles are similar to the modified bitumen used on flat or nearly flat roofs. In this instance, however, the material is molded into slates that overlap each other, just like natural slate roofing. Rubber, however, is highly water-resistant, relatively easy to install, and is often lighter than natural slate. Rubber slate roofs are also easier to repair and are much more resistant to impacts. 

Is Slate Roofing Expensive?

Slate roofing costs will vary, of course, depending on where you live and the design of the roof. We’ll break down the materials costs and installation costs per square, which is 100 square feet. Be advised, all of these designs may require some additional reinforcement or other expenses. Here is a breakdown of the common costs for materials and labor:

Natural Slate

For natural slate expect to pay anywhere from 500.00-2000.00 per 100 square feet, installed.

  • Materials: $500.00-$2000.00 per square
  • Labor: $650.00-$1800.00

Fiber/Cement Slate

For fiber cement slate. expect to pay anywhere from 1000.00-3000.00 per 100 square feet, installed.

  • Materials: $700.00-$1400.00
  • Labor: $300.00-$1600.00

Synthetic Slate

For synthetic slate you can expect to pay anywhere from $1500.00-$3000.00 per 100 square feet, installed.

  • Materials: $1000.00 – $1600.00
  • Labor: $500.00 -$1400.00

Concrete Slate

For concrete slate you can expect to pay anywhere from $1200.00-$2300.00 per 100 square feet, installed.

  • Materials: $900.00 – $1800.00
  • Labor: $300.00 – $500.00

Rubber Slate

You can expect to pay anywhere from 1100.00-2850.00 per 100 square feet, installed.

  • Materials: $700.00 – $1600.00
  • Labor: $400.00 – $1650.00

Slate Roofing Maintenance Costs

Slate roofing guarantees range from about 50 years to a lifetime. However, this lifespan assumes rigorous maintenance, which can cost anywhere from a few hundred to a few thousand annually, depending on your roof and location.

Generally, concrete roofs will require the most maintenance, at about 1000.00 per year. Synthetic slate will usually be the least expensive version to own, at about 300.00 per year for soft washing and repairs.

Are There Any Slate Roofing Alternatives?

The most common alternative to slate (and tile) roofing is fiberglass/asphalt shingles because they are less expensive to install and do a great job. Fiberglass/asphalt shingles are available that mimic several other materials in appearance, such as wood shakes and terra cotta tiles without the expense. 

However, most homeowners invest in a slate roof for its longevity and look, not the cost, which is the main advantage of fiberglass/asphalt roofs.

How Does a Slate Roof Compare to a Fiberglass/Asphalt Roof?

Natural slate roofs and fiberglass/asphalt roofs share little in the way they perform, are installed, or cost. Generally speaking, a home that is a candidate for a slate roof will be upscale, expensive, and rarely seen on starter homes.

Slate roofs require design considerations within the framing due to the weight, so a major financial investment is common.

Fiberglass/asphalt roofs, however, do not generally require additional investment in structural support, are common on starter homes, and can cost less than half the price of natural slate. 

However, a roof built from hard natural slate can literally last two lifetimes, while a fiberglass/asphalt roof’s maximum life is about 40 years. So, the decision often comes down to a cost-to-own calculation to determine the best overall option.

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