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Wood framed chimney chase surrounding factory built metal chimneys (C) Daniel FriedmanBuild / Inspect / Repair a Chimney Chase

How to build, inspect or repair a wood-framed chimney chase.

This article describes wood-enclosed metal chimneys, how a chimney chase should be constructed, and how those structures can be inspected for leaks, damage, or unsafe conditions.

This article describes how to perform a visual inspection of wood framed chimney chases used to enclose factory-built metal chimneys for safety and other defects. Chimney inspection methods and chimney repair methods are also discussed.

InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers, products, or services discussed at this website.

Wood Framed Chimney Chases around Metal & Insulated Metal Chimneys & Flues

Chimney Chase Construction SNAFUs to Avoid

Wood framed chimney chase (C) Daniel Friedman

Our photographs show a typical wood-framed chimney chase constructed to house an insulated metal chimney and/or a Type-B gas vent.

Our photo above shows vinyl siding has fallen off of the chimney chase, permitting leaks into the structure.

Below we show common leaky conditions at the top of a wood-framed chimney enclosure.

The photo below shows an incomplete chimney chase with poor workmanship - incomplete installation of housewrap, missing chimney flashing, and who knows what at the chimney top.

Wood framed chimney chase (C) Daniel Friedman

...

Metal chimney top leaks (C) Daniel Friedman

The most common defect we find at wood-framed chimney chase ways is an improperly-constructed top flashing that is not sloped to drain properly (shown below).

Leaky metal top on wood framed chimney enclosure (C) Daniel Friedman

Often people try to fix a leak at the the chimney top by smearing on roofing mastic (above right). We find that this is not a durable repair.

Leaks in chimney top sealant (C) Daniel Friedman

A close-look at the top of a mastic-coated wood-framed chimney chase may show that the top is still concave, sloping in towards the chimneys and that the combination of heat and sunlight has dried and cracked the sealant. (Photos above and below).

Leaks at the top of a wood framed  chimney enclosure (C) Daniel Friedman

...

Interior of a wood framed chimney enclosure without the metal chimney  (C) Daniel Friedman

Because the top of chimneys is not readily accessible, leaks in this location may remain undiagnosed for too long, risking insect damage, rot, and mold in the structure below.

The result is leaks inside of the chimney chaseway where water may lead to a damaged and unsafe fireplace insert or heating appliance, rot, and insect damage.

Our photo (left) shows how the interior of a wood-framed chimney chaseway may be constructed using common framing lumber and drywall. In this particular chase no chimney has (yet) been installed.

But leaks at the top of this structure wet the drywall sides leading to a (hard to see) mold contamination.

How to Build a Wood-Framed Chimney Chase

Watch out: before buying materials and starting to hammer away at constructing a chimney chase for your home, be sure to check with your local building code officials.

Wood chimney chase at rooftop © D Friedman at InspectApedia.com A building permit is required in most jurisdictions, and the applicable building codes and inspections are important fire safety checks on your chimney chase design and construction.

Common Specifications & Construction Details for a Wood-Framed Chimney Chase

Chimney chase indoor passage through living area (C) Daniel Friedman

Our photo (left) shows the remains of a metal chimney passing through the framed chimney chase enclosure as it passed through the first floor of occupied space in a building that suffered severe damage from a chimney chase fire. The factory-built insulated metal chimney was venting an oil fired heating boiler.

How to Identify Common Leak points & Hazards at Wood Framed Chimney Chases

Metal chimney top leaks (C) Daniel Friedman

How to Replace a Defective Chimney Chase Pan & Installing a Listed Decorative Chimney Top Shroud

Rusty, undersized chimney chase pan (C) Daniel Friedman Steve Werner - ChimneyKing.com

Details of this topic have been moved to a new article found

at CHIMNEY SHROUDS. Excerpts are just below.

A "Chimney Crown" as popularly used in the fireplace industry may refer to a decorative top shroud installed atop a wood-framed chimney chase, as illustrated here.

Steve Werner, a home inspector and chimney shroud installer with Chimney King [6], a custom chimney "crown" designer in Gurnee IL, provided us with the following wood framed chimney chase top pans along with comments.

Replacememt wood framed chimney chase top pan (C) Daniel Friedman Steve Werner - ChimneyKing.com

In the photo at above left, the top of the chimney chase was too small to allow for a decorative shroud to function safely according to our UL/OMNI test labs certification.

We designed what we call a ‘super chase pan’ to increase the size of the top of the chase so a legal labeled shroud could be placed on top.

At above right we can see the newly fabricated chimney chase top pan that has been corbeled out to increase its footprint or horizontal size dimensions to accommodate a decorative top shroud.

Replacememt wood framed chimney chase top pan (C) Daniel Friedman Steve Werner - ChimneyKing.com

Mr. Werner continues:

In the fireplace industry we use the term “chase pans” for the covering at the top of a wood framed chimney chase.

Our company, ChimneyKing, has bought lots of fireplaces, pipe,  and made many decorative shrouds for testing in these labs to assure that our products are labeled and safe.

Copper chimney rain cap - Chimney King, Wisconsin

Chimney Construction Research & References

IRC FIgure R1003.11 fire clearance

 




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Reader Comments, Questions & Answers About The Article Above

Below you will find questions and answers previously posted on this page at its page bottom reader comment box.

Reader Q&A - also see RECOMMENDED ARTICLES & FAQs

On 2021-09-30 by inspectapedia.com.moderator (mod) - replace a pre-fab chimney run inside of a chimney chase

@Mark Dietrich,

If the existing metal chimney is secured at various points inside the chimney Chase then you will need to gain access to those locations in order to remove it and replace it.

You'll want to check the manufacturer's installation instructions for your new chimney to see the support requirements for the new product as that may be different.

On 2021-09-30 by Mark Dietrich

I need to replace a prefab chimney pipe.
How to I remove the old steal flue pipe? Is straped to the walls of the chimney chase?
Are just a matter of pulling the old pipe out?
Thanks

On 2021-09-17 by inspectapedia.com.moderator (mod) - levels of chimney inspection: Define Level 1, 2, 3

@Jim,

We're glad to be of help and hope you'll keep us posted, perhaps posting also some photos of the existing chimney chase and details about the fire as that may help keep other readers safe.

On 2021-09-17 by Jim

@inspectapedia.com.moderator,
Thanks for your help,
Jim

On 2021-09-16 by inspectapedia.com.moderator (mod) - rafter a fire: equired access points into chimney chase for level 1, level 2, level 3 chimney inspections

@Jim,

Thank you for that added detail;

Depending on the chimney height and construction, an access door, for example close to ground level, is not going to give view of the condition of the entire chimney exterior (running in the chaseway) because the chimney chase may be separated into segments by fire blocking.

Be sure that you discuss this limitation with your chimney sweep.

The entire chimney flue interior can, of course, be inspected by a chim-scan type camera.

It is also important to understand the cause of the chimney fire that already occurred, in particular in a COA where there may be common building materials, methods, installations of heating equipment, and even maintenance (by the same company and even technician) - look for those condtions in other occupancies, heating equipment, not just at the chimneys.


For other readers, as the CSIA notes,

Definition of 3 Levels of Chimmey Safety Inspection & What's Included

Define: Level 1 chimney inspection,

your chimney service technician should examine the readily accessible** portions of the chimney exterior, interior and accessible* portions of the appliance and the chimney connection.

Your technician will be looking for the basic soundness of the chimney structure and flue as well as the basic appliance installation and connections. The technician will also verify the chimney is free of obstruction and combustible deposits.

A Level 2 inspection is required

when any changes are made to the system. Changes can include a change in the fuel type, changes to the shape of, or material in, the flue (i.e. relining), or the replacement or addition of an appliance of a dissimilar type, input rating or efficiency.

Additionally, a Level 2 inspection is required upon the sale or transfer of a property or after an operation malfunction or external event that is likely to have caused damage to the chimney. Building fires, chimney fires, seismic events as well as weather events are all indicators that this level of inspection is warranted.

There are no specialty tools (i.e. demolition equipment) required to open doors, panels or coverings in performing a Level 2 inspection.

A Level 2 inspection shall also include a visual inspection by video scanning or other means in order to examine the internal surfaces and joints of all flue liners incorporated within the chimney. No removal or destruction of permanently attached portions of the chimney or building structure or finish shall be required by a Level 2 inspection.

When a Level 1 or Level 2 inspection suggests a hidden hazard and the evaluation cannot be performed without special tools to access concealed areas of the chimney or flue, a Level 3 inspection is recommended.

A Level 3 chimney inspection

addresses the proper construction and the condition of concealed portions of the chimney structure and the flue

to which we have added, it may be necessary to make more than one access openings to gain view of all portions of the chimney chase interior and chimney exterior within the chaseway.

A Level 3 inspection addresses the proper construction and the condition of concealed portions of the chimney structure and the flue

to which we have added, it may be necessary to make more than one access openings to gain view of all portions of the chimney chase interior and chimney exterior within the chaseway.

On 2021-09-15 4 by Jim

@inspectapedia.com.moderator,
Hi,
Thanks for your reply. We had a fire in one of our buildings. The cause was undetermined and listed as accidental. We want to install access doors so our chimney sweep can do a Level III inspection on the remaining chase of the building. We have Level II inspections done every other year and we would like to have a Level III inspection done.
Thanks,
Jim

On 2021-09-13 by inspectapedia.com.moderator (mod) - We can't find an off-the-shelf fire rated exterior door that has stainless steel hinges

@Jim,

I'm not certain that I have the correct understanding of your project, but

If you are making an opening in a wood chimney chase like those discussed here, you are not accessing the actual chimney itself, just the wood enclosure to it.

If that's the case,

as long as your access opening is weatherproof (so you won't damage the chimney chase by leaks and thus make it unsafe),

and provided your opening cutout doesn't harm the structural components of the chimney chase

and provided your opening cutout does not subvert any fire-blocking that may have been required in the chimney chase

I would expect you could make a weatherproof door out of the same materials used construct the chase itself,

and that your local building or fire inspector will approve it.

There are also available pre-fab access panel frames and doors of various sizes made for indoor or outdoor use and that can be built into the chimney chase frame.

Why are we making this chimney chase opening?

See details of chimney access or cleanout doors

at CHIMNEY CLEANOUT DOOR 

On 2021-09-13 by Jim

Hi, regarding chimney chases at our ski mountain COA, we are looking to install exterior access doors on the chases. Can you tell me if the access doors need to be fire rated? We are looking at a non-fire rated stainless steel door with stainless steel hinges.

We can't find an off-the-shelf fire rated exterior door that has stainless steel hinges that will not rust. Our COA is in Vermont.
Thanks,

On 2021-05-31 by mak.church (mod) - articles on chimney installation for a "buck stove"

@leddyhonda00, For this change in your plans, I would refer you to the following articles:

1) Readers Q&A Section (specifically the numerous Tatyana exchanges) https://inspectapedia.com/chimneys/Chimney-Re-Lining-Repairs.php#QA

2) Convert Zero Clearance Fireplace to Woodstove Safe installation of ... https://inspectapedia.com/chimneys/Woodstove_Installation.php

3) Fire Clearances for Woodstoves, Pellet Stoves, Coal stoves. Heat ... https://inspectapedia.com/chimneys/Woodstove_Fire_Clearance_Codes.php

Let us know if you have additional questions.

On 2021-05-30 by leddyhonda00

@inspectapedia.com.moderator, @Leddyhonda00@gmail.com,

I rethought my plan and will just be doing a zero clearence buckstove unit. Still installed is the 10" flue pipe as well as 14" surrounding the 10" all the way to the top.

The buck stove calls for 103ht rated6" stove pipe. Could i use 6" flex liner instead and drop it into the existing flue piping.

On 2021-05-30 by inspectapedia.com.moderator (mod) - how to make the chimney chase fire resistant

Opening for zero clearance fireplace in a wood framed chimney chase (C) InspectApedia.com leddyhonda@Leddyhonda00@gmail.com,

Sorry Leddy but because the risk that you could burn down the house and burn up its occupants by making a mistake, I cannot advise that you think you can, without an on-site expert, make that old fireplace insert area fire-safe for an arbitrary installation of some unknown heater in the future.

More often the installer will read the zero-cleareance fireplace installation instructions with care to see its dimensions and the required clearance to combustibles for that specific heater.

You don't want to simply start adding "fireproof" materials to the existing opening before knowing what's going into it, or your new appliance may simply no longer fit.

A free-standing woodstove can become enormously hotter than your old fireplace insert and has different fire-clearance requirements than a zero-clearnce fireplace insert - for example, typically three feet from the woodstove to any combustible materials.

You would have to either use a fire-inspector-approved heat shield or remove all of the combustible materials in the area completely.

Also

Watch out
: there is no assurance that that metal chinmney (of which we see only a tiny bit of an extension) is fire-safe and rated for use with your woodstove.

To install a woodstove in most jurisdictions you need a building permit and work must be done to local fire-code specs.

On 2021-05-30 by Leddyhonda00@gmail.com

I have a wood framed fireplace chase. I just pulled out an old zero clearence wood fireplace and want to make the chase non combustible. Any reccomendations with this process? I want to install a free standing woodstove

On 2021-03-22 by danjoefriedman (mod) - masonry fireplace chimney is sinking, can I replace it with a wood framed chase & metal flue?

@george k michaels, sure.

On 2021-03-22 by george k michaels

my email is gjltg66@yahoo.com----have a heatalator wood burning fireplace with a masonary chimney--chimney is sinking and pulling away from the house--

can i remove the masonary chimney and replace it with a wood framed chimney with a double or triple flue--as i said it is a wood burning fireplace--thank you

On 2020-05-10- by (mod) - how to remove a wood chimney chase surrounding a metal chimney

Jerry,

Before offering an opinion I'd need to understand what problem we are solving, and what construction is present.

On 2020-05-10 by jerry

how to remove wood chases from house prefab chimney

On 2019-07-22 - by (mod) - raccoon got into our chimney chase

Yes I'd open the chase from outside to remove the dead raccoon; else you'll live with a smell and possibly a health concern. Since some raccoons carry rabies you need to assure the dead animal is remove taking proper precautions.

I'd study the fireplace and chimney plans and take a few measurements to cut a sufficiently large access opening in the outer face of the chimney chase to give adequate access; enlarge it if necessary; you can finish the job by building a trimmed removable panel to cover the cutout opening.

Post some photos of the chimney chase (one photo per comment) and of what you find inside and I can comment further.

More about raccoons in buildings is at

RACCOONS in the ATTIC

On 2019-07-21 by John D.

We have a plywood framed wood chimney chase that is sheathed with shiplap.

A raccoon got into the top of the chase through the cricket connection to the chase and apparently worked its way into the chase proper. I heard it fall down the chimeny and land on the fire box.

We've heard some movement, but that stopped quickly and it looks like it died. How would you recommend we open up the side of the chasse to get at the animal to either let it out or remove the carxass?

On 2019-07-12 by Chase cover over faux stucco

Hello,
Would you be able to tell me if we need to put a stainless steel chase cover over our chimney, which was recently redone using a faux stucco material? We had a chimney service come out for an estimate, but they said we do not need a chase cover (due to the faux material).

I am worried that down the line, this will be a problem. Thank you.

On 2018-11-11 - by (mod) - where to find the leak at a wood framed chimney or chimney top

Anon

I would check the obvious and the common leak points such as a bad Chimney Cap, a bad top sealer shroud, leaky flashing where the chase abuts the building or roof.

If none of those shows the slightest hint of likely leak point then you may need to find someone who has a remote camera or even a Chim scan camera that can inspect the interior of the chase.

On 2018-11-11 by Anonymous


Hi Dan. I should have clarified the type of leak. I am having a water leak. I can hear water slowly dripping on the firebox when it rains. The water the flows throught the firebox and into the main part of the fireplace.

The water isnt coming through the flue, the leak is in the chase somewhere....So i cant visually see where it is coming from. The chase is similar to the "super chase pan" the one in the pictures above. Is there a good way to pinpoint a water leak without completely ripping out the firebox? I am at a loss for how to find the water leak.

Thanks for any suggestions.
Rob

On 2018-11-09 - by (mod) -

Rob

It's unclear just what sort of leak you are describing: flue gases, inadequate combustion air, what?

I don't assume the chimney needs to be replaced; but you should have it inspected by a certified chimney sweep who can tell you what's wrong and what repairs (or possibly re-lining if it's an older masonry flue) is needed.

Meanwhile to be safe don't use the gas log fireplace and leave fuel to it shut OFF.

And be sure you have working smoke and CO detectors properly located and tested.

On 2018-11-09 by Rob

I have a prefab fireplace with gas logs. I recently discovered it is leaking. I am not sure how long this has been happening.

I replaced the chase cover and it is still leaking the same as before. The chimney is on the side of the house. Any suggestions for how i could find out where the leak is coming from without replacing the entire chimney? Thanks for any help


...

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