chimney clearance from house

**Steve C.** · 03-26-2012, 10:52 PM

How far should the clearance be from a cinder block (or brick for that matter) chimney be from the side of a house. Most of the time they appear to be right up against the home. Yesterday I saw one that was about an inch or so away from the house tied to it by two metal straps. No adverse conditions were noted as far as leaning. What are the requirements and correct methods for attaching a masonry chimney to the side of a house / building? I'm getting different answers looking around this site.

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**John Kogel** · 03-27-2012, 07:20 PM

It is correct to have a gap. I will let Bob Harper tell you the requirement, whether it is 1 or 2", as I'm not sure and I'm in the White North.

The gap can be closed off on either side of the chimney with trim. But if they do that, they should leave a small gap at the top for migratory brown bats.

**Jerry Peck** · 03-27-2012, 07:33 PM

2" between masonry chimney and combustible material, as I recall.

**Bob Harper** · 03-27-2012, 08:10 PM

1" clearance to combustibles on exterior chimneys; 2" clearance on interior chimneys. This is an exterior chimney so 1" meets the requirement.

As long as the chimney is stable, this stand-off is fine. Pay special attention to how the appliance passes through the wall while maintaining clearances and how it attaches to the chimney and flue.

That metal band is merely cosmetic. In seismic zones, bands and bond beams are designed just to hold the chimney together long enough to allow egress--not to defy gravity or wind.

I've seen chimneys like this done properly on Ft. Jackson, SC from WWII.

**John Kogel** · 03-27-2012, 09:33 PM

Thanks, Bob. I was thinking those nailed straps are not holding that 2 ton concrete phallus from falling any time it wants to.

And I wasn't kidding about the bats, either. They will fly north from Mexico every spring to places just like that, to hang out and eat mosquitoes.

**BridgeMan** · 03-27-2012, 10:36 PM

"Cosmetic straps" is another term for "flimsy," right?

Those shown don't look like they'd support most of my ex-wives.

**Jerry Peck** · 03-28-2012, 03:56 PM

Originally Posted by Bob Harper

1" clearance to combustibles on exterior chimneys; 2" clearance on interior chimneys. This is an exterior chimney so 1" meets the requirement.

As long as the chimney is stable, this stand-off is fine. Pay special attention to how the appliance passes through the wall while maintaining clearances and how it attaches to the chimney and flue.

Bob,

It looked like the standoff was combustible trim?

I could be mistaken though - have been before and will be again.

**Bob Harper** · 03-28-2012, 07:41 PM

By standoff, I didn't mean that 2x6 rough sawn board with the metal strap nailed into it. That is too close. I meant how the chimney itself stands off from the building without continuous contact.

**Jerry Peck** · 03-28-2012, 08:43 PM

Originally Posted by Bob Harper

By standoff, I didn't mean that 2x6 rough sawn board with the metal strap nailed into it. That is too close. I meant how the chimney itself stands off from the building without continuous contact.

Just checking, the trim board is what my objections was to, and not being sure about the 2" clearances, which you did clarify as being 2" interior and 1" exterior - thank you.