Excessive offset from vertical

Heating · Metal Chimneys or Vents · printed page 173 (PDF page 174)

Book index entries

Excessive Offset from Vertical Excessive Offset from Vertical on Metal Chimney Offset From Vertical Metal Chimney Metal Vent

Text in the illustration

wood
gas
30° maximum
offset joints are vulnerable to overheating, creosote buildup and moisture penetration
if the joints are visible, pay particular attention to them
60° maximum (not allowed in all jurisdictions)
cross section
wood stove
gas furnace

Generated explanation

A house cross section compares an exterior metal chimney serving a wood stove with an exterior metal vent serving a gas furnace. Both vertical runs have angled offsets near the floor framing and extend above the roof with caps. Enlarged details show the offset joints and indicate maximum angles from vertical of 30° for wood and 60° for gas, with the gas allowance noted as not permitted in all jurisdictions. The illustration warns that offset joints are vulnerable to overheating, creosote buildup, and moisture penetration, and directs inspectors to pay particular attention to visible joints.