It may be hard to think of roofing work as “fun,” but slate roofing can be both fun and creative when standard installation techniques are set aside and new ones are employed. Standard American slate roofs include field slates that are all the same length and width and usually the same color. Yet, slate roofing allows for a number of variations, including length, width, shape, color, thickness, and recycled content. All of these variations can be blended on one roof — the combinations are endless.
The technique is simple enough. On a standard installation, say all 18 inch long slates, the field of the roof is chalked for the exposure on 18” slates, usually with a 3 inch headlap. That exposure is 7.5 inches, so the chalk lines are set 7.5 inches apart up the roof deck. Now, let’s add 20 inch and 22 inch slates to the mix. They are also installed on the same chalk lines, but the extra length is left to simply hang down. Because the extra slate length creates extra headlap, these longer slates can also be lifted above the chalk line an inch or two in order to adjust the appearance of the finished roof.
Add a variety of colors, which, in the U.S. include various shades of gray, purple, mottled green and purple, red, “sea green,” various shades of green, and black, in whatever combination suits your desire. And make sure you are using a variety of widths, such as 9 inch, 10 inch, 11 inch, 12 inch and 14 inch. If you want to throw some thicker slates into the mix, go ahead. Same for salvaged, weathered slates — they can add some character.
In the end you can obliterate any semblance of uniformity on the roof. Or you can install a more conservative style that retains some uniformity. The advantages of this roof style include a very tight roof due to the extra headlap, not to mention the unique, one-of-a-kind artistic character of the roof. You can also take a mix of sizes and colors of slates that are lying around left-over and make a beautiful roof out of them. You can create a color scheme that suits your needs, matches your building, or just appeals to your sense of artistry.
There is a trick to the system, however — blend the slates on the ground before you send them up onto the roof. Let’s say you’re installing 1/3 18 inch, 1/3 20 inch and 1/3 22 inch (long) slates. Then for every 12 slates sent up to the roof, there will be four of each length. If your 18 inch slates are two colors, or maybe half new and half salvaged, then, of those four, two are one type and two are the other, etc. You have to figure out your blend ahead of time this way, then blend the slates on the ground — a job usually done by the ground worker(s), and an important job as well (Figure 1). The slates are then sent up already pre-mixed so the installers just have to look at each one to make sure they’re grabbing the correct width.
Each overlying slate should lap the underlying slate down the center, if possible, although a 3 inch lateral overlap is permissible. The installers are also looking at the lengths and colors, trying to not lay the same length and/or same color beside each other. In other words, the installer is looking at every slate prior to nailing it. This is what creates the artistry.
For this article, we have installed six such roofs on small buildings using different combinations of lengths, widths, colors and recycled content. Each roof is totally unique in its own way. Download this article.
Sources of New Roofing Slates
Sources of Salvaged Roofing Slates
See also: Staggered
Butt Slate Roofing
Slate Roof Installation Information
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