Chimney Framing Clearance

Framing the chimney chase.

Chimney framing clearance.

The nfpa calls for an 18 clearance to combustible walls for single wall stove pipe. Typically uses 2x4 structural members sheathed with osb or plywood exterior building sheathing. Masonry chimney fire clearance from wood framing as carson dunlop associates at reviewers sketches above illustrate proper masonry construction leaves space between wood framing members and the chimney or where framing rests on or in a masonry chimney at least 12 of solid masonry should separate the chimney flue from the nearest wood framing member. The new ibc international building code that most places have adopted says that combustible framing must be 2 clear of the firebox or chimney.

This is a bit of an odd measurement and chimney clearance case because the chimney side is actually about 8 away from the roof edge. It appears the original installation allows about 1 5 if clearance in a framed pass through the ceiling in other words the current fiberglass insulation is about 1 5 away leaving the lower chimney chase able to breath or release heat. Double wall stovepipe is used when you don t have 18 or more clearance from combustibles. Combustible sheathing can touch the masonry to close the gap in an exterior wall for example if it is at least 12 from the nearest point in the firebox or flue.