One aspect of the disclosure is a shingle including a first bituminous sheet at the bottom surface of the shingle, the first bituminous sheet having a lower edge disposed at the lower end of the shingle, the first bituminous sheet having one or more slits extending from the lower edge of the first bituminous sheet toward the upper end of the shingle; and a second bituminous sheet at least partially laminated to a top surface of the first bituminous sheet, the second bituminous sheet having a lower edge disposed adjacent the lower end of the shingle, the second bituminous sheet having one or more tabs being defined by one or more notches formed in the second bituminous sheet, each notch extending away from the lower edge of the second bituminous sheet.