Minimum spacing of roof sheathing to chimney

[msteger]

I can't seem to recall what the minimum spacing allowed for roof sheathing to a chimney/metal vent. Today, I saw plywood directly up against a wood burning fireplace's chimney and called it out as a potential pyrolysis and fire hazard, but can't recall the exactly minimum requirement. Is it 2" min spacing b/w chimney and framing or plywood?

Believe it or not, the seller also had plywood nailed up against the chimney in the garage as well.

Thanks in advance.

[Bain]

The manufacturer's stickers usually mandate a minimum of 2" clearance from combustibles. I always take a photo of the sticker to show my customer.

[msteger]

What sticker are you talking about? Can't say I've every seen a sticker on a chimney.

[Bain]

This guy.

Image Insert:

588.55 KB

Image Insert:

611.8 KB

[msteger]

Thanks. I don't recall seeing stickers on metal vents very often. The 2" spacing only pertains to B (double walled metal) vent, correct? The single walled stuff needs to have more clearance like 6~ 8" if I recall.

[StevenT]

I also believe that the "chaseway" should be fireproofed between floors.

[randynavarro]

Urrgg.

Big photos.

[Bain]

Sorry RE the photo size. I was in a wicked hurry.

[hausdok]

Hi John,

Just resize them on your own computer then go back to your post, click the "edit" icon, delete the old photos, upload the resized ones, and then click "submit changes."

ONE TEAM - ONE FIGHT!!!

Mike

[msteger]

The 2" spacing is required for B vents (double walled) and masonry chimneys.

[Neal Lewis]

Matthew, a B vent for gas fired equipment requires one inch of clearance. Single wall is six inches for gas and 9-18 inches of clearance for oil fired equipment, depending.

[msteger]

Thanks. Found the info in Code Check Complete (pp. 138 and 167).