Chimney & Skylight Flashing Calculator

Calculate flashing requirements for roof penetrations including chimneys, skylights, vents, and pipes. Get accurate material lists for base flashing, step flashing, counterflashing, and pipe boots.

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Calculator

Penetration Type *

Chimney Width *

Width of chimney across the front (in inches)

Chimney Depth *

Depth of chimney from front to back (in inches)

Skylight Width *

Rough opening width of skylight

Skylight Length *

Rough opening length of skylight

Skylight Mount Type *

Pipe Diameter *

Number of Pipes *

Material Type *

How Flashing Calculations Work


                    Base Flashing = (Width + 12) / 10

Front pan pieces (10 per piece)


                    Step Flashing = ((Depth × 2 + Width) / 5)

Step flashing pieces per side


                    Counterflashing = (Width + Depth) × 2 / 10 + 4

Counter flashing with corners


                    Back Pan = (Width + 12) / 10

Back pan flashing


                    Cricket Required: Width > 30

Cricket needed for chimneys over 30 inches wide

Chimney flashing requires multiple layers of protection. The base flashing (front pan) catches water at the bottom, step flashing channels water down the sides, and counterflashing嵌入在砖石中。Back pan flashing provides additional protection on the upper side.

A cricket (or saddle) is required for chimneys wider than 30 inches to prevent snow and ice buildup behind the chimney.

Reference: ARMA and NRCA installation guidelines