Typical Slate Roof Shingle Exposure

Overlap is an important consideration to take when evaluating slate shingle exposure area.

Slate shingle widths, lengths and thicknesses come in a variety of sizes. Thinner shingles are smaller, while larger shingles must be thicker. The key to their durability is in the installation, including how much of the slate shingle area is exposed to the elements.

Roof Exposure

Roof exposure is measured by the square foot. To cover the entire area of the roof, the total slate tile square foot area will need to be greater than the entire roof area.

Headlap

Slate shingle overlap each other. It is essential that top shingles overlap those below them by a minimum of 3 inches. This overlap is called a headlap. Headlaps less than 3 inches make the roof susceptible to leaks and deterioration.

Sidelap

Likewise, sidelaps are lateral overlapping of the slate shingles on top of each other. Like headlaps, sidelaps should be a minimum of 3 inches or the roof will be susceptible to leaks and deterioration.

Slate Tile Exposure

Headlap and sidelap, therefore, must be taken into account with slate shingles. For example, a 12 by 12 inch slate shingle will provide a 4 1/2 inch slate exposure area.

References

• Traditional Roofing Magazine: How to Preserve a Slate Roof

Resources

• Amlink Marble: Slate Roofing