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In North America there are roughly 36 standard slate sizes. Standard lengths are 12", 14", 16", 18", 20", 22" and 24". Standard widths vary somewhat depending on the lengths. The narrowest common width is 1/2 the height (for example: 12" x 6", 14" x 7", 16" x 8", etc.). The widest common width is 14". 13" dimensions are traditionally avoided, presumably out of superstition.
| Table of Standard North American Roofing Slate Sizes |
| Length |
Width |
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24
24
22
22
22 |
14
12
14
12
11 |
Oversized Slates
Available, but typically carry longer lead times and slightly higher prices.
|
20
20
20
20
18
18
18
18
18
16
16
16
16
16
16 |
14
12
11
10
14
12
11
10
9
14
12
11
10
9
8 |
The Most Commonly Produced Sizes
Frequently installed as "random width" roofs where all widths of a single length are comingled, or as a "single size" roof. The most commonly used sizes for "single size" roofs are in bold.
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14
14
14
14
14
14
12
12
12
12
12
12
12 |
12
11
10
9
8
7
12
11
10
9
8
7
6 |
Undersized Slate Sizes
These sizes are typically produced as "fall out" or "spin offs" from the fabrication of the larger target sizes. When making 16", 18" or 20" slates any pieces that have broken corners or that won't make the intended size will get trimmed down to make the next largest useable size. Because they accumulate as a byproduct, they are typicalyy prices more favorably than larger sizes. They often have more "texture" than larger sizes and at some quarris they'll tend to be more frequently out of square or off size as they are re-trimmed on manual trimmers. If these sizes have to be produced as a "target" size they'll often carry a price premium as producing them on purpose takes more labor because there are more pieces per square.
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Other sizes can be made as a special order but these slates would command a premium price. There are limits, of course, but we have seen roofing slates as large as 30" x 24" X 1 ½" and as small as 9" x 6" X 3/16".
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