I own and operate a small roofing company, Stewardship Slate, that specializes in the restoration and repair of slate roofs. We work primarily in the downtown area of Burlington, Vt., where more than half of the houses are roofed with slate—slate that was most likely quarried from a nearby region known as the Slate Valley. Running approximately 24 miles along the Vermont-New York border, this area has been and continues to be one of the largest sources of roofing slate in the U.S. (see map, below).
Ryan Catania of Stewardship Slate finishes up restoring a 120-year-old slate roof in Burlington, Vermont. Photo by Michael Dillon
What makes the Slate Valley distinct is that slate found there comes in a variety of colors, shades, and textures. Green, sea green, gray, red, purple, and black slate come from this area, as well as slate in variegated mixes of these colors. Also, this slate has a reputation of being among the best in the world and is highly durable, lasting as long as 200 years. For our restoration work, we typically use salvaged slate from a couple of family-run slate companies located in the heart of the valley. The weathered salvage slates are a better color match and thickness (they are thinner than today’s standard) for the roofs we work on, which are almost all at least a century old. See author’s JLC July-August/21 article, “Slate Roof Restoration” for information about slating tools and techniques.
The Slate Valley is one of the five major slate regions that produced slate in the U.S. (Monson, Maine and Peach Bottom, Pennsylvania-Maryland no longer produce roofing slate). Straddling the Vermont-New York border, this area has been and continues to be one of the largest sources of roofing slate in the U.S (left). The chemical and mineral composition of the slate in this region produces a variety of colors, which is unique in the world (right). According to the Slate Association, “Chlorite produces green slate, hematite the purples, carbon the grays and blacks, and hematite and iron oxide the reds. Slate can be known as ‘weathering’ and ‘non-weathering’, or ‘fading’ and ‘non-fading’ … the terms are often used interchangeably. Unfading slates more or less maintain their original color on the roof. Weathering is used to describe slates that would show various percentages of color change slowly as the slates were exposed to the elements.” Illustration (left) by Tim Healey, adapted from The Slate Roof Bible by Joseph Jenkins. Photo (right) by Tim Healey with permission from the Slate Valley Museum.
Becoming a slater. I grew up in a town just north of Slate Valley and always had a passing awareness of it—my closest exposure came from playing high school soccer against the Fair Haven, Vt., “Slaters” and traveling through the area to visit family. Little did I know that this region would factor heavily into my professional life so many years later.
After college, I worked as a carpenter and then a construction project manager for 12 years before I got into the slate roofing business in 2010. I was always interested in historic preservation and there was a demand for slaters in the Burlington area. Although it’s somewhat dangerous work and requires a lot of patience, I’ve come to really enjoy the pace of slating.
1
of 6
The exposed slate ledge shown here is known as the Glen Lake Syn…
The exposed slate ledge shown here is known as the Glen Lake Syncline located in West Castleton, VT. In the early 1800s, farmers working fields along the Vermont-New York border below Lake Champlain encountered similar outcroppings of slate. Initially, the region’s “surface” slate—left exposed by glacial scouring during the Great Ice Age—was quarried on a small scale for mill stock and foundation stone. See “Geology of the Champlain Valley” for the geologic origins of this metamorphic rock. Photo by Tim Healey
Three miles southwest of the Glen Lake Syncline, the first slate…
Three miles southwest of the Glen Lake Syncline, the first slate quarry in western Vermont was opened in 1839. The quarry owners began manufacturing roof slate 1848 and by 1850 there were five companies in Rutland County, Vermont producing the roofing product. Photo by Tim Healey
A slate quarry in Granville, NY. circa 1920. As quarry pits got …
A slate quarry in Granville, NY. circa 1920. As quarry pits got wider and deeper, carriages run on steel cables held aloft by “quarry sticks” were needed to hoist the stone out of the maturing quarries. According to The Slate Roof Bible by Joseph Jenkins, “By 1872, over 11,000 tons of roofing slate were being shipped annually from Poultney, Vermont, amounting to about 35,000 squares of roofing— enough to cover roughly 3,000 average houses.” Image courtesy of the Slate Valley Museum
A slate quarry in Granville, NY. circa 1920. Shanties line the l…
A slate quarry in Granville, NY. circa 1920. Shanties line the left side of the yard while stacked slate piles line the right. The completion of the Rutland and Washington Railroad line through Castleton, Poultney, and Granville in 1852 vastly expanded the market for slate beyond the local area to other parts of the northeast and the Midwest. By the turn of the century, up to 250,000 squares of roofing slate were being shipped annually from the slate valley; peaking at 425,000 squares in 1908. Image courtesy of the Slate Valley Museum
Tight edge nailing that matches the plans’ shear wall schedule…
Tight edge nailing that matches the plans’ shear wall schedule and a 1/8-inch gap are details that a building inspector will look for first (above left). The nailing schedule can vary from wall to wall, so some framers mark up panels so it’s clear to the crew exactly what the nailing should be. Here (above right), 3/12 refers to edge and boundary nailing every 3 inches and nailing in the field every 12 inches along studs.
A carriage hoists up a slate block from the bottom of the Eureka…
A carriage hoists up a slate block from the bottom of the Eureka Quarry in North Poultney, VT circa 1948 (left). Eureka Quarry workers split blocks with hammers and chisels (right). See video, “Heavy Lifting: A Human & Technological History of Moving Slate from Quarry to Market”, for information about the unique history of the roof slate industry along the Vermont-New York border. Images courtesy of the Slate Valley Museum
A connection to the old country. A few years into running my business, I found out that my great, great grandfather was a slater in Scotland and I have family from the old country still in the business (Scotland, Ireland, England, and more famously Wales have pockets where slate is still the predominant roofing material). I now stay in touch with that side of the family via a fellow Gen-X-er Scotsman cousin who is a fifth-generation slater.
1
of 17
Extracting slate from the earth is still done from an open mine …
Extracting slate from the earth is still done from an open mine called a “pit”. Access roads allow for safer mining—gone are the days of workers having to climb in and out of the pit on rickety, makeshift ladders. Waste rock or “rubbish” is seen on the right of the photo. Manufacturing slate into products such as roof slates, floor tile, countertops, and flagstone has a 90-percent waste factor. Photo by Tim Healey with permission from Camara Slate Products
Large pieces of slate or “blocks” are transported from the p…
Large pieces of slate or “blocks” are transported from the pit to a nearby processing mill via a big-haul truck or smaller dump trucks. Water, seen here on the right, needs to be pumped out of the pit every day.
The access road, looking north (left). A drilling rig or “John…
The access road, looking north (left). A drilling rig or “John Henry” is used to core holes in the slate deposit for blasting (right, lower left of photo). Slate deposits in the region lay at roughly 45-degree angle in the ground. Quarriers in the past predominantly worked the highest quality slate deposits—the resulting slate back then could be split as thin as 3/16 of an inch as opposed to today’s minimum thickness of ¼ to 3/8-inch. Modern tools and transportation allow today’s slate companies to manufacture slate products from lesser quality deposits (deposits that quarriers of yesteryear would not touch because they didn’t have the technology to do so). The slate from this quarry has a 75- to 100-year product lifespan, which passes the S1 standard (ASTM C406).
A worker uses an air hammer to split a slate block down to 6-inc…
A worker uses an air hammer to split a slate block down to 6-inch-or-less thicknesses in order to fit under the cutting saw arbor. Upon excavation, slate has to be managed carefully. It has a certain amount of moisture content and its cleaving planes can be ruined if the stone freezes or it lays out in the sun too long and dries out; wind is also a factor in freezing and drying. Each fall, slate blocks are stacked in the storage building beyond to maintain production in winter.
The split blocks are loaded onto a conveyor leading to the cutti…
The split blocks are loaded onto a conveyor leading to the cutting rooms.
The block is cut to the desired width and lengths with a water-c…
The block is cut to the desired width and lengths with a water-cooled diamond blade.
The cut pieces are conveyed into the splitting area.
An unchanged technique from the past; a worker hand splits slate…
An unchanged technique from the past; a worker hand splits slate with a hammer and chisel (left). Here, he starts splitting a cut piece of unfading gray slate starting at an inner third point (right). He’ll then split the cleaved-off third piece into the desired roof slate thicknesses.
Here, a worker splits a cut piece of purple slate (left, right)….
Here, a worker splits a cut piece of purple slate (left, right). Splitting is just one of many quality-control points along the production line. Uneven cleaving planes and imperfections, such small seams of flint, render many a cut piece of slate useless.
The split slate is sent to the finish mill on pallets in “chip…
The split slate is sent to the finish mill on pallets in “chip form” (sawn on four sides to a certain length and width) ready for trimming. Here, “breakdown” pallets holding various sizes of purple slate are in the foreground and “book form” pallets of uniformly cut unfading mottled green and purple slate are in the background.
The trimmer cuts the slate down to its finished size (left), put…
The trimmer cuts the slate down to its finished size (left), putting a chamfered edge on all four sides of the slate; the chamfered edge creates a shadow line when roof slate is installed. The trimmer blade comes in two sizes (right), the smaller blade is used to trim thinner slate, the larger for thicker material. The blade consists of carbide bits soldered onto a steel blade.
Fastener holes in the slate are made with a hole puncher. The mo…
Fastener holes in the slate are made with a hole puncher. The motorized hole puncher (not in use) has a cam which oscillates the punching bits (left), while an old-style punch uses a spring-loaded arm to make a striking motion (right). The slate is punched from the back, which creates a blow-out hole in the front that the nail head countersinks into.
The holing process for thicker material, such this ¾-inch-thick…
The holing process for thicker material, such this ¾-inch-thick piece of unfading mottled green and purple slate, is done with a hammer-drill with a long masonry bit.
The front of a 1-inch-thick unfading mottled green and purple sl…
The front of a 1-inch-thick unfading mottled green and purple slate after hammer-drilling the punch holes. Pricing for a square roof slate ranges widely due to color selection and thickness. The least expensive slate is roughly $400 a square, while the most expensive goes for over $2,000 a square.
Forklifts are used to ferry orders awaiting delivery and the acr…
Forklifts are used to ferry orders awaiting delivery and the acres inventory around the slate yard. Pricing for a square roof slate ranges widely due to color selection and thicknesses. The least expensive slate is roughly $400 a square, while the most expensive goes for over $2,000 a square.
Slate is typically transported by semi-trailer trucks. The load …
Slate is typically transported by semi-trailer trucks. The load shown here is destined for Dallas, Texas.
Shawn Camara of Camara Slate Products, Inc. (left, foreground) s…
Shawn Camara of Camara Slate Products, Inc. (left, foreground) shows the public how to hand split slate during a “Slater Day” event at the Slate Valley Museum in June of 2023. Photo by Tim Healey
The roof slate industry along the Vermont-New York border began in earnest in the mid-1800s. According to the Slate Valley Museum in Granville, N.Y., “In 1839, slate deposits were discovered near Fair Haven, but quarrying was found impractical and uses for slate were limited. By the mid-1840s, things began to change, and a strong future for the industry looked promising. The roof of a barn one mile south of Fair Haven was the first to be covered with slate in 1848. It was feared the barn would not withstand the weight of the stone. The barn is still standing today and the same slate roof is intact.”
All labor was done by hand in the early days. Workers armed with hand shovels filled large, oak-plank boxes to move material. Steam power came to the valley a couple of decades later, then electric power in 1913 (both power sources helped ferry cut slate and waste pieces around the quarries with less toil). Eventually, air-powered tools such as jackhammers arrived and increased production many times over that of the early, punishing days of slate quarrying.
Today, the industry employs modern heavy equipment and adheres to strict safety protocols, though slate blocks are still split into roof slates with hammer and chisel, the one remaining task done by hand.