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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.
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.
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.
Metal chimneys that pass up adjacent to a building exterior wall must be supported at five-foot intervals by brackets that secure the chimney to the building wall structure.
Metal chimneys that pass up through a building roof are supported by a bracket assembly securing the above-roof chimney to the roof surface and additional support may be required inside the building.
In roof-supported metal chimney installations, in mobile home chimney installations, and in cathedral ceiling installations of metal chimneys, a ceiling support box or special roof support is required.
Typically a hanging-support bracket secures the chimney at the point where it passes through the roof deck or through building floors as well. You can see the indoor-side of that roof-passage assembly at left. 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.
How to Install a Metal Chimney Roof Support Bracket
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.
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.
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.
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 - Where to buy metal chimney support brackets
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Questions & answers or comments about bracing & support requirements for metal chimneys & flues.
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Mark Cramer Inspection Services Mark Cramer, Tampa Florida, Mr. Cramer is a past president of ASHI, the American Society of Home Inspectors and is a Florida home inspector and home inspection educator. Mr. Cramer serves on the ASHI Home Inspection Standards. Contact Mark Cramer at: 727-595-4211 mark@BestTampaInspector.com
John Cranor is an ASHI member and a home inspector (The House Whisperer) is located in Glen Allen, VA 23060. He is also a contributor to InspectApedia.com in several technical areas such as plumbing and appliances (dryer vents). Contact Mr. Cranor at 804-747-7747 or by Email: firstname.lastname@example.org
Thanks to Luke Barnes for suggesting that we add text regarding the hazards of shared chimney flues. USMA - Sept. 2008.
Arlene Puentes, an ASHI member and a licensed home inspector in Kingston, NY, and has served on ASHI national committees as well as HVASHI Chapter President. Ms. Puentes can be contacted at email@example.com
Roger Hankeyis principal of Hankey and Brown home inspectors, Eden Prairie, MN, technical review by Roger Hankey, prior chairman, Standards Committee, American Society of Home Inspectors - ASHI. 952 829-0044 - hankeyandbrown.com
NFPA #211-3.1 1988 -
Specific to chimneys, fireplaces, vents and solid fuel burning appliances.
NFPA # 54-7.1 1992 -
Specific to venting of equipment with fan-assisted combustion systems.
Gas Appliance Manufacturers' Association has prepared venting tables for
Category I draft hood equipped central furnaces as well as fan-assisted
combustion system central furnaces.
National Fuel Gas Code, an American National Standard, 4th ed. 1988 (newer edition is available) Secretariats, American Gas Association (AGA), 1515 Wilson Blvd., Arlington VA22209, and National Fire Protection Association (NFPA), Batterymarch Park, Quincy MA 02269. ANSI Z223.1-1988 - NFPA 54-1988. WARNING: be sure to check clearances and other safety guidelines in the latest edition of these standards.
Fire Inspector Guidebook, A Correlation of Fire Safety Requirements Contained in the 1987 BOCA National Codes, (newer edition available), Building Officials and Code Administrators International, Inc. (BOCA), Country Club HIlls, IL 60478 312-799-2300 4th ed. Note: this document is reissued every four years. Be sure to obtain the latest edition.
Uniform Mechanical Code - UMC 1991, Sec 913 (a.) Masonry Chimneys,
refers to Chapters 23, 29, and 37 of the Building Code.
New York 1984 Uniform Fire
Prevention and Building Code, Article 10, Heating, Ventilating, and Air Conditioning Requirements
New York 1979 Uniform Fire Prevention & Building Code, The "requirement" for 8" of solid masonry OR for use of a
flue liner was listed in the One and Two Family Dwelling Code for New
York, in 1979, in Chapter 9, Chimneys and Fireplaces, New York 1979
Building and Fire Prevention Code:
"Top Ten Chimney (and related) Problems Encountered by One Chimney Sweep," Hudson Valley ASHI education seminar, 3 January 2000, contributed by Bob Hansen, ASHI
"Rooftop View Turns to Darkness," Martine Costello, Josh Kovner, New Haven Register, 12 May 1992 p. 11: Catherine Murphy was sunning on a building roof when a chimney collapsed; she fell into and was trapped inside the chimney until rescued by emergency workers.
"Chimneys and Vents," Mark J. Reinmiller, P.E., ASHI Technical Journal, Vol. 1 No. 2 July 1991 p. 34-38.
"Chimney Inspection Procedures & Codes," Donald V. Cohen was to be published in the first volume of the 1994 ASHI Technical Journal by D. Friedman, then editor/publisher of that publication. The production of the ASHI Technical Journal and future editions was cancelled by ASHI President Patrick Porzio. Some of the content of Mr. Cohen's original submission has been included in this more complete chimney inspection article: InspectAPedia.com/chimneys/Chimney_Inspection_Repair.php. Copies of earlier editions of the ASHI Technical Journal are available from ASHI, the American Society of Home Inspectors.
Natural Gas Weekly Update: http://tonto.eia.doe.gov/oog/info/ngw/ngupdate.asp Official Energy Statistics from the U.S. Government
US Energy Administration: Electrical Energy Costs http://www.eia.doe.gov/fuelelectric.html
Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair
Ceramic Roofware, Hans Van Lemmen, Shire Library, 2008, ISBN-13: 978-0747805694 - Brick chimneys, chimney-pots and roof and ridge tiles have been a feature of the roofs of a wide range of buildings since the late Middle Ages. In the first instance this ceramic roofware was functional - to make the roof weatherproof and to provide an outlet for smoke - but it could also be very decorative.
The practical and ornamental aspects of ceramic roofware can still be seen throughout Britain, particularly on buildings of the Victorian and Edwardian periods. Not only do these often have ornate chimneys and roof tiles but they may also feature ornamental sculptures or highly decorative gable ends. This book charts the history of ceramic roofware from the Middle Ages to the present day, highlighting both practical and decorative applications, and giving information about manufacturers and on the styles and techniques of production and decoration.
Hans van Lemmen is an established author on the history of tiles and has lectured on the subject in Britain and elsewhere. He is founder member and presently publications editor of the British Tiles and Architectural Ceramics Society. Available at the InspectAPedia Bookstore.
Chimney & Stack Inspection Guidelines, American Society of Civil Engineers, 2003 - These guidelines address the inspection of chimneys and stacks. Each guideline assists owners in determining what level of inspection is appropriate to a particular chimney and provides common criteria so that all parties involved have a clear understanding of the scope of the inspection and the end product required. Each chimney or stack is a unique structure, subject to both aggressive operating and natural environments, and degradation over time. Such degradation may be managed via a prudent inspection program followed by maintenance work on any equipment or structure determined to be in need of attention. Sample inspection report specifications, sample field inspection data forms, and an example of a developed plan of a concrete chimney are included in the guidelines. This book provides a valuable guidance tool for chimney and stack inspections and also offers a set of references for these particular inspections.
NFPA 211 - 3-4 - Clearance from Combustible Material
NFPA 54 - 7-1 - Venting of Equipment into chimneys
Brick Institute of America - Flashing Chimneys
Brick Institute of America - Proper Chimney Crowns
Brick Institute of America - Moisture Resistance of Brick
American Gas Association - New Vent Sizing Tables
Chimney Safety Institute of America - Chimney Fires: Causes, Effects, Evaluation
National Chimney Sweep Guild - Yellow Pages of Suppliers
Carson, Dunlop & Associates Ltd., 120 Carlton Street Suite 407, Toronto ON M5A 4K2. Tel: (416) 964-9415 1-800-268-7070 Email: firstname.lastname@example.org. The firm provides professional home inspection services & home inspection education & publications. Alan Carson is a past president of ASHI, the American Society of Home Inspectors. Thanks to Alan Carson and Bob Dunlop, for permission for InspectAPedia to use text excerpts from The Home Reference Book & illustrations from The Illustrated Home. Carson Dunlop Associates' provides extensive home inspection education and report writing material.
The Illustrated Home illustrates construction details and building components, a reference for owners & inspectors. Special Offer: For a 5% discount on any number of copies of the Illustrated Home purchased as a single order Enter INSPECTAILL in the order payment page "Promo/Redemption" space.
TECHNICAL REFERENCE GUIDE to manufacturer's model and serial number information for heating and cooling equipment, useful for determining the age of heating boilers, furnaces, water heaters is provided by Carson Dunlop, Associates, Toronto - Carson Dunlop Weldon & Associates Special Offer: Carson Dunlop Associates offers InspectAPedia readers in the U.S.A. a 5% discount on any number of copies of the Technical Reference Guide purchased as a single order. Just enter INSPECTATRG in the order payment page "Promo/Redemption" space.
The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 25th Ed., 2012, is a bound volume of more than 450 illustrated pages that assist home inspectors and home owners in the inspection and detection of problems on buildings. The text is intended as a reference guide to help building owners operate and maintain their home effectively. Field inspection worksheets are included at the back of the volume.
Special Offer: For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
Special Offer: Carson Dunlop Associates offers InspectAPedia readers in the U.S.A. a 5% discount on these courses: Enter INSPECTAHITP in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
The Horizon Software System manages business operations,scheduling, & inspection report writing using Carson Dunlop's knowledge base & color images. The Horizon system runs on always-available cloud-based software for office computers, laptops, tablets, iPad, Android, & other smartphones