Fire Stopping Requirements at Chimney Passages Through Building Floors
Why we need fire blocking & combustible clearances

FIRE STOPPING at CHIMNEY PASSAGES - What are the Fire stopping or fire-block details needed where a chimney passes through building floors?
- Chimney inspection, diagnosis, and repair
CHIMNEY INSPECTION CHECKLIST - separate article
CHIMNEY CAP & CROWN - separate article
CHIMNEY CHASE - separate article
CHIMNEY SHROUD FIRE - separate article
CHIMNEY SHROUDS - separate article
FIREPLACES & HEARTHS - separate article
FIREPLACE INSERTS - separate article
FIREPLACE INSPECTIONS - separate article
FIREPLACE INSPECTION PRE-FAB - separate article
PYROLYSIS EXPLAINED - separate article
Questions & Answers about fire stopping in buildings where chimneys pass through floors
References

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Chimney construction: fire stopping. This article describes the basic requirement for fire stopping needed where building chimneys or flues pass through building floors. Fire stopping is a measure taken to slow the spread of fire between building floors - an event that could occur at openings cut to permit a chimney to pass through from one floor to another.

Fire stopping at Chimney Passage Through Building Floors

Sketches courtesy of Carson Dunlop. Readers of this article should also see Fire Clearances for Masonry Chimneys and Fire Clearances for Metal Chimneys as well as FIRE CLEARANCES, Single-Wall Metal Flues. This article series on chimneys, chimney construction, and chimney safety provide 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.

Due to the drying of lumber and movement in structures the chimney shaft must remain free of any ties into the framing of the building. The space between the shaft and the building is or can be sealed with "fire code" [fire-rated] sheetrock or metal flashing if a fire stop is required between floors.

Fire stopping at a chimney (C) Carson Dunlop

Fire stop at metal chimney (C) Carson Dunlop

Chimneys that pass through several floor levels of a home may be required to be fire stopped at each penetration. Typical fire stops are sheet metal or fire code sheetrock.

Carson Dunlop's sketch shows fire stopping at the fire-clearance gap provided between the chimney and wood floor framing (above left) and fire stopping around a metal chimney as it passes through building floors (above right).

Other Common Examples of Indoor Fire Clearance Safety Hazards

Fire clearance too close to combustibles (C) Daniel Friedman

We often find flue vent connectors routed too close to combustible wood framing or, as in our photo at left shows, too close to other combustible materials such as the foam insulation just a few inches above this flue pipe.

Many building fire safety codes specify that the fire clearance between a flue vent connector and combustibles needs to be that specified by the appliance manufacturer.

Indeed some modern heating appliances permit pretty close clearances, as little as a few inches.

In the absence of a manufacturer's specification, we want to see at least 18" between the flue and the nearest combustible surface.

The reason for Fire Clearances from Wood Materials

The reason that building codes specify a healthy distance between wood materials (or other combustibles) and flue vent connectors is not just that the heat from the flue will immediately set the wood on fire. Rather it is also that wood that has been heated over time, even to the relatively low temperature of 200 to 300F, will be chemically affected to become more readily combustible.

Details are at PYROLYSIS EXPLAINED - separate article

Frequently Asked Questions (FAQs) about fire stopping requirements in building walls, stairways, chimney chases etc.

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Technical Reviewers & References

Related Topics, found near the top of this page suggest articles closely related to this one.

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: johncranor@verizon.net
Carson, Dunlop & Associates Ltd., 120 Carlton Street Suite 407, Toronto ON M5A 4K2. (416) 964-9415 1-800-268-7070 info@carsondunlop.com. 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:
- Commercial Building Inspection Courses - protocol ASTM Standard E 2018-08 for Property Condition Assessments
- Home Inspection Education Courses including home study & live classes at eleven colleges & universities.
- Home Inspection Education Home Study Courses - ASHI@Home Training 10-course program.
  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 Home Reference Book, a reference & inspection report product for building owners & inspectors.
  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.
- The Home Reference eBook, an electronic version for PCs, the iPad, iPhone, & Android smart phones.
  Special Offer: For a 5% discount on any number of copies of the Home Reference eBook purchased as a single order. Enter inspectaehrb in the order payment page "Promo/Redemption" space.
- 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.
- 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.
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
NFPA 211 - Standards for Chimneys & Fireplaces, NFPA 211: Standard for Chimneys, Fireplaces, Vents, and Solid Fuel-Burning Appliances, 2006 Edition (older editions and standards are found at the same bookstore)
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/chimneys.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
Buurman, P., K. G. J. Nierop, X. Pontevedra-Pombal, and A. Martínez Cortizas. "Molecular chemistry by pyrolysis–GC/MS of selected samples of the Penido Vello peat deposit, Galicia, NW Spain." Developments in Earth Surface Processes 9 (2006): 217-240.
Li, Shiguang, Shaoping Xu, Shuqin Liu, Chen Yang, and Qinghua Lu. "Fast pyrolysis of biomass in free-fall reactor for hydrogen-rich gas." Fuel Processing Technology 85, no. 8 (2004): 1201-1211.
Oasmaa, A., and E. Kuoppala. "Fast pyrolysis of forestry residue. 3. Storage stability of liquid fuel." Energy & fuels 17, no. 4 (2003): 1075-1084.
Rowell, Roger M. The chemistry of solid wood. Washington, DC: American Chemical Society, 1984.
Shafizadeh, Fred. "The Chemistry of Pyrolysis and Combustion" in The Chemistry of Solid Wood Chapter 13, pp 489–529, Advances in Chemistry, Vol. 207 ISBN13: 9780841207967eISBN: 9780841223899 Publication Date (Print): May 05, 1984
Shafizadeh, Fred. "Chemistry of pyrolysis and combustion of wood." Prog. Biomass Convers.;(United States) 3 (1982).
Shafizadeh, Fraidoun. "Pyrolysis and combustion of cellulosic materials." Advances in carbohydrate chemistry 23 (1968): 419-474.
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
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Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair

Our recommended books about building & mechanical systems design, inspection, problem diagnosis, and repair, and about indoor environment and IAQ testing, diagnosis, and cleanup are at the InspectAPedia Bookstore. Also see our Book Reviews - InspectAPedia.

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.

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Building inspection education & report writing systems from Carson, Dunlop & Associates Ltd

Fireplace & Chimney Design, Repair Books - Fireplaces, Chimneys: design, repair
Fireplace & Chimney Inspection Books - Inspecting and diagnosing chimney problems, fireplace problems, chimney & fireplace standards
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 211: Standard for Chimneys, Fireplaces, Vents, and Solid Fuel-Burning Appliances, 2006 Edition (older editions and standards are found at the same bookstore)
Principles of Home Inspection: Chimneys & Wood Heating (Principles of Home Inspection), Carson Dunlop
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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