Field Slates of Uniform Widths:
Purpose: To create a uniform slate roof by utilizing slates of a single length, width, and thickness that maintain horizontal course and alternating vertical joint (bond) lines
Jointing: Adjacent slates in a course may be laid slightly touching or with a small gap +/- ¼” to enhance aesthetics, ensure adequate slate widths at details, or to accommodate offset of vertical joints
Materials: Slates of one length, width and thickness. Eg: 18” long x 10” wide x ¼” thick (wider slates can be used at valleys & hips)
Details: Try to avoid using slates narrower than 6” at rakes and other details. This can be achieved by subtly increasing the joint spacing between slates or by employing slightly narrower slates in courses approaching the detail, or by installing wider slates at the detail. In all cases, attention should be given to maintaining the required offset and alternating vertical joint lines. Where unavoidable, narrow slates may be bedded in sealant to prevent blow off.
Layout: The field should be laid out to both horizontal course chalk lines and frequent vertical joint chalk lines. Layout should accommodate the appropriate exposed length and width of slates in each course and maintain alternating vertical joint lines at rakes, valleys, walls, dormers, roof penetrations and other roof details.
Blending: It is always important to blend slate from multiple pallets when installing a slate roof to ensure a proper blending of tones, regardless if uniform or random width slates are being installed.
Field Slates of Random Widths:
Purpose: A random width slate roof utilizes slates in a variety of widths that maintain horizontal course lines and random vertical joint (bond) lines.
Jointing: Adjacent slates in a course may be laid tight or with a small gap +/- ¼” to enhance aesthetics, ensure adequate slate widths at details, or to accommodate 3” offset of vertical joints.
Materials: Slates ranging in width from ½ the slate’s length and up to 14” wide (e.g., 18” long x 9, 10, 11, 12 and 14” wide. A random width roof can consist of as little as two or as many as seven widths.
Details: Try to avoid using slates narrower than 6” at rakes and other details.
Layout: The field should be laid out to horizontal course chalk lines dictated by the appropriate exposed length of slates in each course. The minimum offset of 3 inches should be maintained as slates are laid in each course, while also minimizing the vertical alignment of joints with nearby slates in courses below.
Blending: The number of pieces of slate of each width available is used to determine the blend of widths used as the slate is installed. This serves to best utilize the slate available, while creating an aesthetically pleasing roof and avoiding repetitive patterns
Graduated Field Slates:
Appearance: A graduated slate roof traditionally utilizes slates of a variety of sizes to create a roof of diminishing slate lengths, widths and thicknesses. Courses of longer/thicker/wider slates are installed at the eaves, with shorter/thinner/narrower slates placed in courses as installation progresses up slope.
Jointing: Adjacent slates in a course may be laid tight or with a small gap (approx +/- ¼”) to enhance aesthetics, ensure adequate slate widths at details, or to accommodate alignment of vertical bond lines.
Materials: Depending on roof size and design, slates in three or more consecutive lengths and of random widths are employed. Thicknesses can commonly range from 1” to 1/4” in at least three standard thickness graduations.
Details: Try to avoid using slates narrower than 6” at rakes and other details
Layout: The field should be laid out to horizontal course lines in the number of courses as determined by the available quantity of each length and thickness of slate.3-inch minimum offset should be maintained as slates are laid in each course, while also minimizing the vertical alignment of joints with nearby slates in courses below.
Blending: The number of pieces of slate of each length, width and thickness delivered to the site is used to determine the roof layout and the blend of sizes used as slate is installed. This serves to best utilize the slate available, while creating an aesthetically pleasing roof and avoiding repetitive patterns.