By National Slate Association. 

In use for over 400 years in North America, slate has gained quite a reputation in the roofing industry. See what myths can be debunked. 

When roofing material has been around for as long as slate has been, it comes as no surprise that there are stories and concerns that surface over time. However, when determining the best material to use, you need to ensure you have information that is accurate. We’ve compiled the eight most popular myths around slate shingles in the industry.  

Myth 1: Slate lasts forever 

While exceptional durability is a characteristic of slate shingles, with some slates having an expected service life of over 200 years, the fact is slate is like all other natural and human made materials in that they must, according to the laws of thermodynamics, transition from a state of order to disorder, from high entropy to low entropy. The service life of slate shingles depends largely on the geology of the slate – its mineral composition and the heat and pressure it was subjected to during its formation – a process known as metamorphism. 

Myth 2: No maintenance required 

Implicit in the myth that slate lasts forever is that a slate roof does not have to be maintained. Again, not true. Like all roofs, slate roofs do require some maintenance. The level of maintenance needed typically varies depending on whether the roof is in the early, middle or late stage. One of the beauties of a slate roof, however, is that repair is a relatively straight forward process, wherein a damaged slate can be easily removed using a tool called a ripper and a new, matching, slate shingle inserted in its place. 

Myth 3: Slate fines found in gutters is an indication of poor-quality slate 

Slate fines – tiny pieces of slate ranging in size from that of a pin head to a small button – typically appear in gutter troughs within the first several months of a slate roof’s installation. Slate fines result from trimming, cutting and nail punching operations that occur during fabrication at the quarry and during installation on the roof. Fines remaining on the roof after completion will gradually be washed downslope and into the gutters with each passing rainfall. 

Myth 4: A few broken slates one year after installation is an indication of poor workmanship 

As discussed in the first myth, it is not unusual for broken slates to occur a year or two after installation. Cracks can occur in the slate shingles as slaters trim, punch, install and walk on the slate during the construction process. Many of the cracked slates are identified as the slaters break down their means of access and are replaced with new, matching slates. Some cracks, however, are too fine to be identified, or are located in the concealed portion of the slate shingles. It is these few slates that can break and slide out of position early in the roof’s service life. 

Myth 5: Attic stock will break down quickly because it is not exposed to the weather 

It is true that blocks of slate are more difficult to split into shingles when they lose their quarry sap (inherent moisture within the stone) and quarries make every effort to prevent this from happening. And hot-cold cycling can result in the transformation of certain impurities contained within some slates into gypsum, thereby resulting in an expansion in volume and delamination over long periods of time, but it is not true that slates stored indoors become more brittle and/or less durable. 

Myth 6: There are no slate roofing contractors anymore 

A shortage of construction workers has confronted the building trades in general since at least the turn of the twenty-first century as older workers retire and fewer young people enter the field, preferring less physically demanding work opportunities. While there are fewer slaters in the field today than 25-years ago, the trade is not dead. One only needs to look as far as the National Slate Association's website for a list of slate roofing contractors by state. 

Myth 7: Slate roofs are too heavy 

Slate roofs are heavy. The weight of a slate roof, of course, depends on the thickness of the slate. A quarter-inch thick slate weights approximately 935 pounds per square (per 100 square feet of roof area), or 9.35 pounds per square foot (psf), when laid with a standard 3-inch headlap. A half inch thick slate weighs approximately 18.70 psf. At these weights, the loads can be too great for standard post World War II construction. At the very least, if a structure never had a slate roof, a licensed structural engineer should evaluate the roof framing and associated load paths to determine if a slate roof is feasible, or whether supplemental framing or other modifications are needed. 

Myth 8: Natural roofing slate is no longer available 

Although there has been a consolidation in the number of commercial slate quarries and a number of quarries and slate types are in transition at the time of this writing (Fall 2022), S1 North American natural slate shingles are very much available in a wide variety of colors and all standard sizes. Slate from the Buckingham district of Virginia, the Vermont/New York district, and the Glendyne quarry of Canada, representing the full range of historical colors – black, green, gray, purple, red, mottled purple and green, strata gray – are in full production and readily available in the marketplace. 

Further info on these myths can be found within this PDF. 

Original article source: National Slate Association

By Evelyn Witterholt. 

Learn all about how slate interacts with fire and if it can be salvaged afterwards. 

It’s common knowledge that slate is fire-resistant, but can it be reused after it interacts with fire? The answer is a bit complicated as there are many factors to consider, such as the condition of the slate or its proximity to fire. The National Slate Association (NSA) outlines all the considerations to make when it comes to reusing slate after a fire in their technical bulletin, “Reuse of Slate Shingles Exposed to Fire”. 

In the bulletin, the NSA outlines the impressive fire-resistant properties of slate roof tiles. For decades, slate roof shingles were considered effective against fire exposure. But in 2009, when it was called into question over whether or not slate was effective against fire when installed over combustible roof decks, the NSA performed further testing. 

The bulletin states that once fire tests were performed again, “Slate shingles installed over a combustible roof deck were once again recognized as having a Class A rating over combustible decks in the 2015 edition of the International Building Code.” 

Although slate tiles themselves will not combust, the question of whether slate exposed to fire can be reused still remains. According to the bulletin, there is no universally accepted answer. A lot of factors must be taken into consideration, including the type of slate used, its age or its condition. 

One consideration the NSA encourages you to take into account is the previous condition of the slate. They state that “a slate nearing the end of its service life, based on age or as evidenced by significant surface delamination, cracking, and broken corners on the exposed faces, is probably not a good candidate for salvage and reuse, regardless of whether it has been exposed to fire, or not.” 

Check out the entire technical bulletin from NSA to learn more about if slate can be reused after being exposed to fire.

By Evelyn Witterholt. 

If you can’t decide between warm terracotta, modern slate and everything else in between, this homeowner’s guide will help! 

Choosing the right material for your roof is no easy task. Even if you’ve narrowed it down to the material you desire, there’s still so much variety to choose from. There’s no doubt about the benefits of tile roofs. In a previous article, we wrote that “roofing tiles are typically made of concrete, clay or slate and can last 50-100 years. They are highly durable and low maintenance.” Not only that, but the look of a tile roof is as timeless as it is durable. 

Here are some things to keep in mind when finding the right tile for your roof: 

Types of tiles 

While there are a lot more subcategories of roof tiles, here are the four main ones: 

Photo credit: National Slate Association 

1 - Slate 

Slate roofing tiles are made from large slabs of rock and are considered some of the longest-lasting and earliest forms of roofing tiles. According to HomeAdvisor, “Slate roofs can and should be routinely built to last at least a century. In fact, 150 years is a reasonable expectation of a roof’s longevity if the roof is properly constructed.” Slate comes in a wide range of looks so the choice comes down to which complements the exterior of your home the best. 

Photo credit: The Durable Slate Company 

2 - Clay 

Clay tiles are one of the more popular tile options, mainly for their classic look and enhanced durability. According to Homes and Gardens, clay tiles have a lower water absorption rate, meaning they’ll be less heavy on a home when wet. They also maintain their color for years even when exposed to elements like heat. 

Photo credit: Tile Roofing Industry Alliance 

3 - Concrete 

Concrete tiles are similar to clay tiles in terms of look and longevity. The major difference between the two is that concrete tiles cost nearly half as much as clay tiles. HomeAdvisor does say that although concrete tiles offer the similar look of clay, they do not hold color as well. 

4 - Composite 

Composite roof tiles are synthetic materials that are manufactured to look like real slate or wood shakes. For example, the synthetic slate products from DaVinci Roofscapes are made from a highly durable polymer that’s designed specifically to withstand all climates.  

Photo credit: DaVinci Roofscapes 

Where to get your tiles 

As previously mentioned, DaVinci offers a wide range of synthetic slate products in a multitude of colors. If you want the real deal with authentic slate and clay roof tiles, check out what All Points has to offer. They have an inventory of over 500,000 square feet of roof tiles and they even offer a tile glazing service if you happen to find the right tile in the wrong color. 

If you are still stumped on which roof tile is right for you, feel free to contact any of the manufacturers mentioned above or even ask one of our roofers through the link below! 

Have a question? AskARoofer.    

Find your local roofing contractor in the RoofersCoffeeShop® Contractor Directory. 

About Evelyn  

Evelyn works as a writer for RoofersCoffeeShop, MetalCoffeeShop and AskARoofer. When she isn’t writing about roofing, she’s either at the gym lifting weights or curled up on the couch watching a movie.