Chimney Flashing Calculator

Step, Apron, Counter Flashing & Cricket Material

Enter the chimney width, depth and roof pitch to calculate step flashing pieces for each side, apron flashing across the downslope face, counter flashing let into the mortar joint, ice-and-water membrane around the opening and cricket material where the chimney exceeds 30 inches across the slope. Chimneys are the most common leak point on an otherwise healthy roof, and the failure is almost always the metal rather than the masonry.