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Dead End Flues or Dead Base Chimney Flue Hazards InspectAPedia®  -     What is a dead end flue or dead base chimney flue Warnings about unsafe blocked chimney flues

This article describes dead base or dead end flues and explains why they can cause heating equipment operating difficulties or why they may be unsafe. A dead end flue is one in which the flue vent connector joins at the very base of a chimney. Debris falling down the chimney can quickly block the flue, prevent proper removal of exhaust gases from the building heating equipment, and can be dangerous.

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.

Dead End Flues or Dead Base Chimney Flue Hazards

Dead End Chimney Flue Clues

• Absence of a chimney cleanout - the chimney may stop right where the flue vent connector enters the chimney.
• Combustion chamber backpressure burns on the heating equipment (photo at left) may indicate that the chimney is blocked (or there are other draft problems such as an open chimney cleanout door)
• Old houses built on stone foundations with no original central heating.
  
  Often when a basement was later excavated or deepened to install a heating boiler or furnace, the only connection into a chimney flue was an entry point at or close to ground level above the basement because the original chimney flue did not extend below ground level.
  
  Look for a chimney that sits atop a stone foundation.
  

• Flue vent connectors (stack pipes or smoke pipes) routed through crawl spaces often enter the bottom of a chimney flue. (Photos above on this page).
• Masonry fragments in the cleanout: if you open a chimney cleanout-door or pull the flue vent connector from a dead end chimney flue, in either case you are looking at the very bottom of the chimney flue.
  
  If you are inspecting a masonry chimney, be alert for discovery of masonry fragments when inspecting or cleaning the bottom of the flue. If a piece of brick, masonry block, concrete, or clay flue tile liner is pulled out of your chimney, ask "where do you suppose this came from?"
  
  If the masonry scrap fell during construction of the chimney it may mean nothing.
  
  But if it fell because the chimney has been damaged, perhaps by water, frost, or during cleaning, then you probably have an unsafe chimney flue - more investigation is in order, promptly.
  
  Certainly if you believe that the masonry scrap found at the bottom of a flue fell during original construction, and if you remove it during cleaning, you should never find another piece in the flue bottom. If you do, the flue has been damaged anew and it is unsafe.

• Chimney use history: if a chimney has been used for a variety fuels, coal, oil, wood, there may be a greater accumulation of debris at the chimney bottom, a mixture of creosote, soot, or even masonry fragments from a flue damaged by corrosive gases and condensate in the flue.
  
  Our photo (left) shows a truly abandoned dead end flue chimney. We changed this building to a direct-vent heating boiler and abandoned the chimney entirely rather than continue to face chimney blockage problems.
• Chimney draft problems: if someone has installed a draft inducer fan because they couldn't get enough draft, the problem could be a blocked flue. Look for back-pressure burns on the combustion chamber. Look for a defeated or sealed-up barometric damper. See details at DRAFT REGULATORS, DAMPERS, BOOSTERS.
• Chimney leak history: leak stains inside the building attic or on any floor, if they are traceable to leaks at a chimney, are reason to be concerned for possible water damage to the chimney as well as to the building. Further investigation may be warranted.
• Chimney cap history: if a chimney has spent part of its life with no cap installed, there is extra risk of water damage to the flue interior. In a masonry chimney damage may appear as frost cracking of the upper flue liners or masonry. In any chimney, there may also be water damage to the heating appliances being vented by that chimney.

Dead end chimney flues are likely to lead to the rusted-out flue vent connector such as we show here. We suspect that the root cause of this unsafe metal heating flue is that it was routed out of the building at or below ground level - into a dead-end chimney. Water from roof spillage or surface runoff have rusted out the flue vent connector. This is an unsafe installation even before we think about the added hazards of fire clearances and adequate draft.

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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
CHIMNEY INSPECTION DIAGNOSIS REPAIR
Chimneys Cleaning Advice, Procedures
Chimney Cleanout Doors
Chimney Crack & Collapse Risks, Repairs
Chimney Draft & Performance
Chimney Inspection Checklist
Chimney Inspection Indoor Procedures
Attic Chimney Inspection
Chimney Inspection Outdoors From Ground
Chimney Crack Detection & Diagnosis
Chimney Inspection Outdoors From Ground
Chimney Height & Clearance
Chimney Inspection Outdoors at Rooftop
Chimney Cap & Crown Inspection
Chimney Types & Materials
Chimney Cleanout Doors
Fire Clearances for Masonry Chimneys
Fire Clearances for Metal Chimneys
Fire Clearances, Single-Wall Metal Flues
Flue Sizing of Chimneys
Fire Stopping Between Floors
Flue Vent Connectors - Boilers, Furnaces
  Blocked Chimney at the Flue Vent Connector
Dead End Chimney Flue Hazards
Extended Too Far into Chimney
  Joint Connections - Single Wall Metal Flues
  Length Limits for a Flue Vent Connector
  Loose, Leaky, Not Sealed, Flue Vent Connector
Plastic Heater Vents
Plastic Vents Goodman HTPV Recall
Rusted Metal Flue Vent Connectors
Slope, Proper Flue Vent Connector
Chimney Inspection: Flue Interiors
Metal Chimneys & Flues
Shared Chimney & Shared Flue Hazards
Fireplace Damage & Unsafe Hearths - Settlement
Moisture Problems Damage Chimneys
Wood Burning Heaters Fireplaces Stoves

• 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
• Principles of Home Inspection: Chimneys & Wood Heating (Principles of Home Inspection), Carson Dunlop
• Woodstove & Fireplace Maintenance & Safety, L. L. Helwig

More Information on Building Diagnostic Inspections and Repairs

• 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

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