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.