How to Choose Slate Shingle Sizes

Slate shingles are produced in various lengths, widths, and thicknesses. The size of slate shingles you use is ultimately a matter of customer preference, but roofers should be prepared to educate the customer on what sizes are available.

Slate roofers can help customers choose the right size shingles if they know the standard sizes of slate shingles, the basic principles of slating a roof, and by performing some measurements and math prior to installation.

Slate shingles standard sizes

The standard dimensions for roofing slate begin at 12 inches in length and increase by 2-inch increments up to 24 inches in length. The standard widths of slate shingles begin at half the length of the slate and increase in 1-inch increments (except for 13-inch widths) as wide as 14 inches. Wider slates are available by special order for installing roof details such as valleys, dormers, and gable ends. You can check out our chart of standard slate sizes here.

While uniform-width roofs are a popular selection, many architects and builders opt for random-width slate roofs, which offer a truly unique roofing aesthetic as assorted widths are blended so that no slate course is exactly alike. Thicknesses and lengths of slates can also be graduated, with longer and thicker slates installed at the eave and shorter, thinner slates installed closer to the ridge. A graduated roof has the effect of making a roof’s lines appear longer than they truly are.

While slate shingles are produced in a rectangular shape, they can be specially trimmed into a variety of designs such as diamond, fish scale, and hexagon. These shapes offer different opportunities for patterns and designs that will make a roof stand out.

Planning the layout

Unlike many other roofing products, slate shingles aren’t sealed together. Slate shingles are overlapped during the installation process to guarantee the roof is watertight. This overlap at the top of the slate is called headlap. Headlap specifically refers to the portion of slate that is covered by two successive courses of slate.

The amount of headlap depends on the slope of the roof, so your first step is to calculate the roof pitch. For roof pitches between 8:12 and 20:12, a three-inch headlap is standard. Roof slopes between 4:12 and 8:12 require a four-inch headlap. Slate shingles are not recommended for any roof slope lower than 4:12.

Also consider that people standing at ground level can see more roof area when looking at a steeper-sloped roof. Steeper-sloped roofs will better accentuate the beauty of the slate shingles.

Side lap refers to the lateral spacing of the slates, where the sides of each slate abut one another against the course below. These side butt joints should be placed as close to the middle of the course below as possible, maintaining at least three lateral inches of space between side butts on the course above or below.

Planning the layout is the most important stage when slating a roof. If done correctly, the rest is relatively easy; if the layout isn’t correctly planned, expect the work to take longer and be less precise.

At North Country Slate, we’re always ready with the best design and technical advice, to ensure that your new slate roof rises to your expectations.

Slate shingle thickness options

Slate roof tiles are available in a range of thicknesses from nominal ¼ inch thickness on the thin side to nominal 1-inch thickness on the heavier side. The standard thickness of slate tiles is from 1/4-inch to 3/8-inch.

North Country Slate also offers a traditionally installed natural slate lightweight roof system available in our North Country Unfading Black.

This lightweight roof system is made possible by the high-quality stone and advanced schistosity of the Quebec-quarried stone, allowing the slate to be split into extremely thin 3/16-inch tiles without compromising the structural strength or durability of the roof system, and is fully backed by our 75-year warranty covering delamination or substantial deterioration of the slate tiles.

For more information on our traditionally installed natural slate roofs, contact us today and let us help bring your vision to life.