Cut a piece of sheet metal, which needs to be rated for fire-stops, to about six inches larger than the hole your stainless chimney goes through. Draw on the center of the sheet a circle the same size as the diameter of your chimney. Cut four evenly spaced diameter lines through the center of the circle to the outside edges.
A fire-stop is a critical component of a chimney. The fire-stop prevents a house fire from burning through the space between your chimney and framing and into the upper floors or the roof of your home. While manufactured fire-stops are easy to find and inexpensive, making your own can be rewarding and allow you a flexibility that's not possible with commercial fire-stops.
Position the fire-stop. Bend the metal triangles up so a hole is in the center of the sheet of metal. Pass the stainless chimney pipes through the sheet metal so that the sheet metal is at the point where the chimney passes through the wood framing of your house. Ensure that the fire-stop blocks all air access and sight lines from one side of the framing to the other.
Affix the fire-stop in place. Screw the sheet metal into the wooden framing. Wrap metal tape rated for high-heat applications around the bent pieces of sheet metal so they adhere tightly to the stainless chimney.
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