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

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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

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 chimneyh 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 bracke 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 Friedmanat 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.

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. 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. 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.
  2. 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.
  3. Finally, the nails or bolts used to secure the roof bracket to the the roof surface are sealed with silicone sealant or an equivalent.

Tall rusty single wall vent (C) Daniel FriedmanThe 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 - Where to buy metal chimney support brackets

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Continue reading at CHIMNEY CHASE CONSTRUCTION or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.

Or see BRACING for MASONRY CHIMNEYS

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BRACING for METAL CHIMNEYS at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

INDEX to RELATED ARTICLES: ARTICLE INDEX to CHIMNEYS & FLUES

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