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Class A Metal Chimney & Flue Inspection, Diagnosis, Cleaning & Repair Guide InspectAPedia®  -     Class A Metal Chimney & Flue Inspection, Diagnosis, Cleaning & Repair Guide Insulated Double Wall MetalBestos™ type chimney inspection & repair Detailed Inspection & Photo Guide to chimney defects Chimney cleaning & repair advice

This article describes how to select, install, and inspect Class-A insulated metal chimneys such as the Insulated Double Wall MetalBestos™ manufactured metal chimney, also called a "zero clearance" chimney.

This website provides detailed suggestions describing how to perform a thorough visual inspection of chimneys for safety and other defects. Chimney inspection methods and chimney repair methods are also discussed. As with most inspection and safety topics, this material may be incomplete. © Copyright 2009 Daniel Friedman, All Rights Reserved. Information Accuracy & Bias Pledge is at below-left. Use links at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website.

Class A Chimneys - Insulated Double Wall MetalBestos™ type

Improper metal chimney installation: As you can see from our photo ( above left), even this superb product can be reduced to shambles when installed by an idiot. The chimney in this photo was not supported, is falling and is unsafe. See Chimney Collapse Hazards & Chimney Support & Bracing Requirements.

This unfortunate collapsing Class-A type metal chimney was the replacement for the abandoned masonry chimney under the corrugated metal roof we show at Chimneys Abandoned Outdoors and that whose remains we showed at Chimneys Abandoned Indoors. It looks as if more than one generation of inexpert chimney installers worked in Dover, NY.

Our photo at above right shows an end view of a section of Metalbestos SS All Fuel Chimney™. The fiberglass insulation is not part of the product and was just left stuffed in that opening.

Carson Dunlop's sketch at left shows a Class "A" chimney, of which our photos are an example. Metalbestos™ type chimneys are available in different diameters, lengths, and with elbows, caps, and supporting base kits. These chimneys are used often to vent oil fired heating equipment as well as woodstoves and zero-clearance or built-in fireplaces. Our photograph at above left shows an installation leaving the insulated metal chimney exposed on the home exterior. While these insulated chimneys may be rated for zero clearance from combustibles by the manufacturer, many building codes require at least a one-inch clearance between the chimney and any combustible materials. Our photo below shows a wood-framed chimney chase that might enclose an insulated metal chimney or a Type-B Gas vent chimney.

Class A Chimney Height Requirements

More complete details about chimney height requirements on buildings including Class A Chimneys is at Chimney Height & Clearance

Class A Chimney Fire Clearance Details

More complete details about Class-A chimney fire clearances indoors can be read at Fire Clearances for Metal Chimneys

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• Additional technical contributors & reference sources for this article are listed below.

Use links just below or at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website.

CHIMNEY INSPECTION DIAGNOSIS REPAIR
CHIMNEY INSPECTION & REPAIR GUIDE
Introduction to Chimneys & Flues
Chimney Types & Materials
Chimney Inspection From Outside - Ground Level
Chimney Separation, Settlement, Leaning, Cracking
Chimney Height & Clearance
Chimney Inspection From Outside - Rooftop
Metal Chimneys & Flues
Class A Chimneys, MetalBestos™
Type B-Vents
Type L Vents
  Chimney Height for Types L & Type B Vents
Triple-Wall Metal Fireplace Chimneys
Super Chimneys, 629 Chimneys
Connecting Metal Chimney Sections
Wood Framed Chimney Chases
Single-Wall Metal Vents & Chimneys
Fire Clearances for Metal Chimneys
  Class A, B-Vent, & 650C Fire Clearances
Wet time & Corrosion in Chimneys, Vents

Indoor Chimney & Flue Inspection Procedures
Indoor Chimney & Vent Connector Fire Clearances
Wood Burning Boilers, Furnaces Fireplaces Stoves
HEATING COST FUEL & BTU Cost Table
Flue Vent Connectors
Rusted Metal Flue Vent Connectors
Proper Flue Vent Connector Slope
Sizing of Chimney flues
Fireplace Damage & Unsafe Hearths
Creosote Deposits - Fire Hazard
Dead End Flues - Dead Base Chimney Hazards
CHIMNEY CRACK & COLLAPSE HAZARDS
How to Inspect Chimney Flues
Chimney Cleanout Door Hazards
Chimney Cleanouts Required
Missing Chimney Cleanout Door
How to Inspect Chimney Flue Interior
ChimScan: Inspecting Chimney Flues by Remote Cameras
Chimney Cleaning Advice
Choices for Re-Lining Masonry Chimneys
Chimney Inspection Checklist
Responsibility of an ASHI Home Inspectors

CO2 TOXICITY
COALSTOVE SAFETY
COMBUSTION PRODUCTS & IAQ
Dead End Chimney Flue Hazards
Definitions of Chimney Types & Parts
DRAFT HOODS - gas fired
DRAFT REGULATORS - barometric dampers
FIREPLACE INSERTS
Goodman HTPV RECALL
HEATING INSPECTIONS
HOME HEATING SAFETY
Lennox WARNING
OIL HEAT SAFETY INSPECTIONS
PLASTIC HEATER VENT
Transite Pipe Chimneys & Flues
UNLINED FLUE INSPECTIONS
Weil McLain RECALL
WOOD STOVE SAFETY

• Thanks to Alan Carson and Bob Dunlop, Carson Dunlop, Associates, Toronto, for permission to use illustrations from their publication, The Illustrated Home which illustrates construction details and building components. Carson Dunlop provides home inspection education, publications, report writing materials, and home inspection services. Alan Carson is a past president of ASHI, the American Society of Home Inspectors.
• 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 ap@octoberhome.com
• Roger Hankey is 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
• Chimney Building Codes and Chimney, Flue, and Appliance Venting Standards
  • 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.
  • GAMA - 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
• Chimney Inspection Checklist, Carson Dunlop, Associates, Toronto, Ontario
• "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.htm. 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 Chimney Inspection, Testing, Diagnosis, & Repair

• Books, Complete List of Fireplace & Chimney Design, Inspection, Repair Books at the InspectAPedia Bookstore.
• 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 Inspection Checklist, Carson Dunlop, Associates, Toronto, Ontario
• 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.
• Fireplaces, a Practical Design Guide, Jane Gitlin
• Fireplaces, Friend or Foe, Robert D. Mayo
• NFPA 211 - Standards for Chimneys & Fireplaces, NFPA
• NFPA 211 - 3-1.10 - Relining guide for chimneys
• NFPA 211 - 3-2 - Construction of Masonry Chimneys
• NFPA 211 - 3-3 - Termination Height for chimneys
• 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
• Principles of Home Inspection: Chimneys & Wood Heating (Principles of Home Inspection), Carson Dunlop
• Woodstove & Fireplace Maintenance & Safety, L. L. Helwig
• ...

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