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California Slate Company, Inc.

3344 Market Street
San Francisco, CA 94114
+1 (888) 994-0842
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Lightweight Roofing System

Let’s not mince words. For all the beauty and durability of a traditional slate roof, it has a drawback. It’s heavy. While that’s not a problem for buildings built to support the weight, many existing homes can require structural upgrades that add to the expense of installation.

SLATE2 is a modern take on a traditional slate roof. An elegant merger between modern and traditional technologies, SLATE2 can reduce the weight of a traditional slate roof by 40%, bringing it under 6 lbs. per square foot which meets standard structural roof specifications. Accordingly, SLATE2 allows most homes to acquire the elegance of a traditional slate roof without requiring structural upgrades. Slate roofs are undeniably beautiful, and slate has proven durability, energy efficiency, and desirable environmental qualities. Now SLATE2, exclusive to The California Slate Company, allows a broader range of buildings to gain the benefits of natural stone as a roofing material.

Most modern construction in California can handle the weight of a traditional slate roof. But California construction standards were different between the 1950s through the 1980s. Even beautiful trophy mansions built during that time often can’t support a traditional slate roof without costly structural upgrades. These homes were often roofed with wood—either cedar shake or cedar shingle—which is significantly lighter than a traditional slate roof. Wood roofs can be very attractive, but they are a known fire hazard. For this reason, when these homeowners need to replace their roofs, they are often forbidden by the fire marshal from using wood as a roofing material. Among the available fire resistant roofing materials, slate is the most attractive and Class A fire rated. SLATE2 offers these homeowners a beautiful alternative to a wood roof that is both fire-resistant and light enough not to require structural upgrades.

How does SLATE2 work? It comes down to how the slate is cut and installed.

SLATE2 Tiles are Cut Differently than Traditional Slate

SLATE2 starts by trimming tiles to a different size than traditional slate while retaining their normal thickness. Side by side, the size difference is clear. SLATE2 tiles are custom cut to work with our SLATE2 interlayment system.

SLATE2 is a take on a slate roofing system that was patented by a couple of Texans in the early 1990s. It is simple and easy to use. Of all the systems out there, this is, by far, the most straightforward to install and, in our opinion, the least likely to leak.

Traditional and Slate2 Tiles compared with dimensions.

SLATE2 Tiles are Installed Differently than Traditional Slate

Traditional slate roofs create a watertight seal by overlapping most of each of the stone tiles. SLATE2 uses a proven membrane as an overlapping interlayment that lies between the stone tiles. This interlayment protects against UV, moisture, and weather infiltration. It also allows for a smaller number of slate tiles to cover the same area. Instead of densely overlapping, SLATE2 positions the stone tiles edge to edge while overlapping only the top of each tile, giving the smooth appearance of a traditional slate roof but without the added weight.

Illustration of SLATE2 Installation with Tiles and Underlayment

SLATE2 results in a 40% reduction in the overall weight of a similar traditional slate roof, easily meeting the standard structural roof specification of less than six pounds per square foot.

This modern system, designed for light-weight bearing construction, has been tested over several decades and provides the same durability to a traditional 100-year slate roof. SLATE2 allows for the same beauty and durability as castles of yore combined with the advanced engineering of a modern age. The California Slate Company is proud to offer the SLATE2 option to our customers.

Benefits at a Glance:

  • Lighter
  • Cheaper
  • Greener
  • Classier

Lighter means more flexibility.

A standard house, initially designed for a lighter roof, can now support the weight of a stone roof without structural upgrades. Perhaps you have an asphalt or cedar or shake roof and you’d like to upgrade? SLATE2 means that you can have the slate roof you’ve always wanted as a direct replacement of your existing roof. If you live in an old house, or are building a new one, SLATE2 provides an extraordinary number of options to give your roof exactly the right feel.

Cheaper on many levels.

  • Less Slate Required: SLATE2 uses less stone than a traditional slate roof while preserving the thickness of the individual stone tiles. This comes down to the pattern of the stone tiles used to cover the roof. In a traditional slate roof, the stone tiles almost entirely overlap each other to form a seal against inclement weather. SLATE2’s system doesn’t require the stone tiles to overlap as much. The interlayment works in tandem with the stone to provide protection against UV, moisture, and weather infiltration. The result is an overall reduction in the amount of stone required per roof. Less stone means less weight, so structural upgrades to support the roof are not necessary. This saves design, material, and labor costs for existing homes and new construction.

  • Durable: SLATE2 uses natural stone tiles from the same sources that The California Slate Company uses for its highly regarded traditional slate roofs. SLATE2 tiles are the same thickness as our traditional slate tiles.

  • Low Cost of Ownership: SLATE2 is long lasting, doesn’t require much maintenance, and enhances property value. SLATE2 roofs don’t degrade with sun or moisture exposure. They look even more distinguished over time, while other roofs simply age and deteriorate.

  • Fire Resistant: Stone tiles are innately fire resistant and Class A fire rated. If you live in a high fire danger zone, a slate roof is a safer choice.

  • Easier to Transport: SLATE2 uses less stone so there is less material to transport to a job site. That translates to savings in transportation and logistics.

Greener is more than just environmentally friendly and sustainable.

  • Long Life: There are slate roofs all over the world with ages measured in centuries rather than decades. A SLATE2 roof is a 100-year roof. A house with a SLATE2 roof doesn’t require the expenditure of resources on a new roof every few decades. That’s greener.

  • Energy Efficient: Natural stone in combination with an insulating barrier increases energy savings for the entire building. Slate is a natural insulator, keeping the inside temperatures stable, and increasing the building’s energy efficiency. That’s greener.

  • Environmentally Friendly: Slate is a natural material formed over millions of years of geophysical processes. It is a natural choice for a roofing material and has withstood the test of time. And slate, as natural rock, is completely recyclable. Not only can it be reclaimed, but as natural rock, it belongs to the ground and won’t fill up a landfill. And SLATE2’s interlayment is made of 100% recycled material. That’s greener.

Classier means more beautiful, distinguished, and historical.

  • Beautiful: Slate is simply a beautiful building material. Available in a variety of colors, weathering characteristics, and textures, Slate is a natural product that adds a distinctive look to any building. No other roofing material beats stone for its elegance.

  • Historical: Slate has been used as a building material not just for centuries, but for millennia. It adorns some of the world’s most cherished palaces, museums, churches, and other buildings. Slate is a beautiful, distinguished, authentic, practical, and ancient building material.

  • Resale Value: SLATE2 allows most homeowners to add a slate roof. Because it is long-lasting and desirable, a slate roof adds to the home’s overall valuation.

Why California Slate?

The California Slate Company is the market leader in finding and delivering the very best slate from quarries around the world. We are very picky about the slate that we sell. We test not only the quality of the rock as it comes out from the mine, but we know from experience how this rock has survived the test of time.

We know slate and we love it. We’ve been working with slate over three decades and have a long track record working with the finest contractors and architects. Our slate is found on the roofs of some of the finest buildings in the United States.

Slate is the most durable roofing material. Nature spends millions of years to compress and metamorphize marine sediments to create this variety of rock. Slate is surprisingly versatile and provides many choices when it comes to color, texture, and weathering patterns. Slate is usually black or gray, but it can also be burgundy, green, and the beautiful shades of autumn. Slate can also be mixed to create artistic effects.

Never artificially colored, each slate tile’s color is as it was when quarried. Some slate is classified as weathering: its color evolves as the building ages. Other slate stays true to its original tone. Depending on the application, weathering or non-weathering slate may be desired. The California Slate Company has hundreds of years worth of data on the weathering of different varieties of slate. Because we offer a wide range of slates to choose from, for both traditional roofs and those using our new SLATE2 system, we can help you select just the right material for your project.

The California Slate Company provides an incredible selection of slates of unmatched quality, combined with our technical expertise, great value, and service.

Now, The California Slate Company’s SLATE2 system brings all its expertise and slate varieties to roofs which couldn’t otherwise manage the weight of a traditional slate roof without structural upgrades. SLATE2 uses the same high quality slate fitted to the roof using a modern installation system.

  • SLATE2 Info Sheet

Product Types Compared
  Weight Durability
  kg. per meter2 lbs. per square Years
Natural Slate 7 mm (¼″ thick) 48 950 120
Natural Slate 5 mm (⅕″ thick) 33 650 100
SLATE2 28 550 120
Clay Tiles 60 1,250 40
Concrete Tiles 55 1,100 30
Fibre Cement 25 500 25
Asphalt Shingle 12 250 20