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Collapsing metalbestos insulated chimney (C) Daniel FriedmanBracing & Support Requirements for Metal Chimneys

Metal chimney & flue bracing & support specifications:

Metal chimneys that are more than 5' tall above the roof (or 6' tall in some jurisdictions) require bracing at the rooftop. This article describes bracing and support requirements for metal chimneys.

Metal chimneys more than 5' tall require bracing that connects the chimney to the building. The crazy chimney shown at page top had visible openings at its tipped joints - this was an unsafe installation.

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Bracing Requirements for Metal Chimneys

Bracing on metal B-vent type chimney (C) Daniel Friedman Wall support bracket for metal chimney (C) Daniel Friedman

Five-Foot Rule for Metal Chimney Bracing

Typical installation instructions and standards require rooftop bracing for metal chimneys that extend five feet or more above the roof surface/

Bracing can stabilize a manufactured chimney or it might stabilize a tall masonry chimney that is wobbly but on a good footing - also review moving/separated chimney repairs

at LEANING CHIMNEY REPAIR METHODS. Photo at above left: metal bracket on a B-type vent metal chimney.

Notice that metallic salts washing off of the metal bracing and other runout of the chimney flashing itself are preventing black algae from growing on some areas of this roof.

[Click to enlarge any image]

At above right is a metal wall bracket to support a tall metal chimney passing along the outside wall of our office.

The chimney installer performed the original installation but the job was not well done. This bracket was later removed and re-installed when the finish siding was placed on the building.

Consistent with other chimney bracket manufacturers' instructions, we bent these brackets to an angle to separate them more widely where they attached to the wall. That change significantly reduced side-to-side wobbling of the metal chimney - a safety detail ignored by the original installers.

Metal chimney support at passage through roof deck (C) Daniel Friedman at CLASS A CHIMNEYS we discuss the collapsing Class-A metal chimney shown at the top of this page.

As you can see, a metal chimney on the outside of the building will also require support listed and designed by the manufacturer.

You can see the indoor-side of that roof-passage assembly above.

In roof-supported chimney installations the support box is installed first, then the chimney is passed through it and secured in place.

Note: where a metal chimney passes through building walls or floors fire blocking or use of a fire-blocking foam insulation may be required by local building codes.

See FIRE STOPPING in BUILDINGS

and

also FIRE CLEARANCES, SINGLE WALL METAL FLUES & VENTS.

How to Install a Metal Chimney Roof Support Bracket

Metal chimney support at rooftop (C) Carson Dunlop Associates

Sketch (above) courtesy of Carson Dunlop. When a roof bracket is installed to support a metal chimney, the installation instructions typically specify:

If the chimney extends more than 5 feet above the roofline, an Extended Roof Bracket must be installed at every 5-foot increment of chimney height above the roofline, leaving no more than 5 feet of chimney extending above the last pipe bracket. - DuraTech metal chimney installation instructions, retrieved 6 June 2015, original source: http://www.fornobravo.com/PDF/duratech.pdf

A "Pipe band", basically a round metal bracket, is slipped around the chimney and is secured by tightening a pinch bolt and nut.

  1. Chimney bracket legs are usually adjustable in length and are attached to flanges or "legs" on the pipe band at the chimney.
  2. The chimney support bracket legs are extended in length to form an angle specified by the manufacturer, roughly 60 degrees, with respect to the vertical chimney.
  3. Extendable chimney support bracket legs should not be set to their full length or the bracket may be too weak.

    Duratech requires that the sliding bracket legs overlap one another by at least three inches.
  4. When extended to approximately 60 degrees the foot of the bracket leg is secured to the roof surface using a roof bracket.

    We prefer to adjust the width between the roof bracket legs (see photo above) so that the roof bracket will be secured through the roof sheathing to a rafter or truss.
  5. Finally, the nails or bolts used to secure the roof bracket to the the roof surface are sealed with silicone sealant or an equivalent.

The very tall single wall metal chimney shown at below left is located on a building in Manhattan and was photographed from the Lotus Club. Although the chimney has bracing, chimney sections are loose at several locations giving a sort of drunken sailor look to this flue.

Examples of Chimney Support Bracing and Brackets & Installation Manuals

Tall rusty single wall vent (C) Daniel FriedmanWhere to buy & how to install metal chimney support brackets

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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 2022-09-02 by InspectApedia-911 (mod) - unsafe installation of metal chimney bracing

@Mary,

From our very limited inspection perspective of just a photo,

1. it looks as if the chimney is "supported" by flexible wires connected to an existing chimney that itself is of unknown safety and maybe a single flat metal brace that resists movement of the round metal chimney towards that iffy ridge-top chimney.

Also we can see that

2. the ridge-level chimney lacks a chimney cap

3. your metal chimney shows signs of severe sooting or creosote formation - a fire risk or a carbon monoxide risk (depending on what's being vented)

4. your metal chimney may have been overheated (and unsafe)

5. the "wires" that pretend to support the down-roof metal chimney provide in essence NO resistance to side-to-side movement,

In sum the "wires" offer resistance to chimney movement only in one or at best two of the four possible directions of movement.

Not a good nor safe installation.

On 2022-09-02 by Mary

Hi I was just wondering if this metal chimney is braced or installed properly.

Metal chimney showing unsafe wiring support (C) InspectApedia.com Mary

On 2021-11-05 by Inspectapedia Com Moderator (mod) - wood stove sauna needs bracing for long exterior chimney

@Damon Hess,

CHIMNEY HEIGHT & CLEARANCE CODE addresses the roof clearance question.

You will see that bracing is actually pretty easy and can be achieved using readily available materials either from your chimney supplier or even from the local hardware store.

On 2021-11-05 by Damon Hess

We're building a wood stove sauna. Our challenge is securing the long side-exit chimney away from the sauna and high enough to meet the 3-2-10 rule. The chimney is at the midpoint of a high-pitched roof that is 3' above the chimney's side exit. The pipe is single wall inside and out, except for the two-wall insulated piece that runs through the wall and an extra 18" to clear the eaves.

Do I really need to run a pipe 5' up from its horizontal exit since the chimney is away from the roof?

SAuna chimney specs (C) InspectApedia.com Damon

On 2021-07-24 by inspectapedia.com.moderator - contact manufacturer for missing parts

@Stan Koziol,

When you are looking for parts like this, the best place to start is with the original manufacturer.

What happened when you contacted them?

On 2021-07-24 by Stan Koziol

I bought a kit from Shasta Vent and only the brace and 4 leg brackets were included. Can you help me find adjustable legs to buy for this kit, or show how to make legs for it? Thank You

On 2021-01-06 by danjoefriedman (mod) - chimney manufacturer will have specific bracing recommendations

Randy

I would be sure to check with the manufacturer of the chimney that I'm going to use as without doubt they have specific bracing systems that fit the chimney exactly correctly.

On 2021-01-06 by Randy Gubersky

I am setting up a greenwood, wood burning boiler on the outside of my shop.I am needing to know what braces to use for attaching the metal chimney to the wall....I have a total of 24 ft of piping [12 ft insulated, and 12 ft double wall]...From ground to top of edge of wall is 16 ft

Duravent example of bracing required for chimneys extending 5 ft. or more above roof (C) Inspectapedia.com adapted from DuraVent cited & discussed in this articleQuestion: Do I have to brace stove pipe if it’s just shy of 6 ft ?

2020/02/21 Tom said:

Do I have to brace stove pipe if it’s just shy of 6 ft (triple wall stainless)

This Q&A were posted originally

at CHIMNEY HEIGHT & CLEARANCE CODE FAQS-5

Reply:

Tom if you are saying that your metal chimney height extends un-supported six feet above a roof surface then IMO it ought to be braced.

Typical metal chimney instructions specify that if the free-standing chimney height is over 5 feet then support brackets are required.

The example below is excerpted from

EXTENDED ROOF BRACKET INSTALLATION

If the chimney extends more than 5’ above the roofline, an Extended Roof Bracket must be installed at every 5’ increment of chimney height above the roofline, leaving no more than 5’ of chimney extending above the last pipe bracket. The Extended Roof Bracket consists of the Pipe Band, the Adjustable Legs, and the Roof Brackets.

On 2018-06-15 by (mod) - material requirement for framing a chimney that is +/- 15 feet in height from the base at the roof.

Metal chimney support at rooftop (C) Carson Dunlop AssociatesCary

Excellent question. It might be possible to stick with the original 2x4 framing, perhaps adding bracing rather than heavier construction, but a requirement for extra bracing or structural reinforcement for a tall wood-chase chimney is a question to take to a local engineer who can look at the entire structure, wind load data, bracing requirements.

I reviewed our chimney bracing articles for general chimney bracing guidelines: see

BRACING for METAL CHIMNEYS https://inspectapedia.com/chimneys/Chimney_Bracing_Metal.php

BRACING for MASONRY CHIMNEYS https://inspectapedia.com/chimneys/Chimney_Bracing_Masonry.php

Also see CHIMNEY CHASE CONSTRUCTION https://inspectapedia.com/chimneys/Wood_Chimney_Chase.php

The illustration above is used with permission of Carson Dunlop Associates, a Toronto home inspection, education, and report-writing firm.

On 2018-06-14 by Cary

Is there a material requirement for framing a chimney that is +/- 15 feet in height from the base at the roof.

The gas log fireplace was originally designed with 2 x 4 framing.

We feel that due to the excessive height (and the fact that a brick veneer will be adhered to the exterior) that the framing should be 2 x 6 for proper support to avoid swaying from high winds.

Please advise....Thanks...Does any one know the framing requirement of a chimney that is +15 foot in height from the base of the roof.

The architect designed 2 x 4 framing for these extra tall chimneys....(even though he designed the rest of the house with 2 x 6 framing)...

We feel that they should be 2 x 6 framing for support to prevent swaying in high winds....Is there any code or rule that addresses the framing requirements for excessively tall chimneys..? Please respond as soon as possible....Thanks..!!

 


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