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

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How to build or inspect 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.

We also provide a MASTER INDEX to this topic, or you can try the page top or bottom SEARCH BOX as a quick way to find information you need.

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

Chimney Chase Construction SNAFUs to Avoid

Wood framed chimney chase (C) Daniel Friedman 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. The photo at above left shows an incomplete chimney chase with poor workmanship - incomplete installation of housewrap, missing chimney flashing, and who knows what at the chimney top.

Our photo at above right 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.

Metal chimney top leaks (C) Daniel Friedman Leaky metal top on wood framed chimney enclosure (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 (above left). 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 Leaks at the top of a wood framed  chimney enclosure (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).

Interior of a wood framed chimney enclosure without the metal chimney  (C) Daniel FriedmanBecause the top of chimneys is not readily accessible, leaks in this location may remain un-diagnosed 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 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

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.

Rusty, undersized chimney chase pan (C) Daniel Friedman Steve Werner - Replacememt wood framed chimney chase top pan (C) Daniel Friedman Steve Werner -

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 corbelled 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 -

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.


Contributor & technical review: Stephen Werner General Manager Chimney King, LLC P.O. Box 8 Gurnee, IL 60031 Corporate (847) 244-8860 Fax (847) 244-8694 Email:


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