Inspection for Damage at the Top of Masonry Chimneys, Antennas on Chimneys, Angled Chimney Flues InspectAPedia® -
Guide to inspection of masonry chimney tops for damage - from the rooftop
Guide to inspection & repair of damaged ceramic clay flue liners at chimney tops
Why we do not mount antennas on chimneys
Issues with angled chimney flues
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This article describes chimney defects and hazards that can be observed from on-roof access, including damage to a masonry chimney top, antennas mounted on chimneys, and angled chimney flue hazards.
A good rain cap or chimney cap (DF's terms) does more than keep out the rain; it also improves chimney draft and prevents downdrafts inside the chimney in windy conditions.
A masonry rain cap such as the one shown in our photo at left can be an effective chimney shelter if it extends past the sides of the chimney and if it is secure.
The chimney shown is a single-wythe flue in Brooklyn, NY. The above-roof section is about to collapse - the chimney is unsafe.
Our photos above show two unsafe chimneys that were still in active use. Notice those missing bricks and lost mortar? Damaged chimney top masonry such as missing bricks and a missing chimney cap were easily spotted from ground level at both the Coolidge Hotel in Vermont (above left) and the private home in New York (above right).
The home inspector or owner should ask, "Where did those bricks go?
are they blocking the flue? Is the flue damaged and unsafe? What repairs are needed before we
install a chimney rain cap?" This chimney may be too short as well - tough to call from
ground level.
Our photo shows a chimney with a cracked, damaged, leaky top seal or "crown" and missing rain cap on the flue.
This chimney needs repairs to its top seal and also it needs a rain cap.
Various experts have proposed design details to avoid cracking at the flue liner/concrete interface at the chimney
top.
Inspecting homes in both cold and hot climates, wherever we've seen chimney top damage
of the sort shown here, it was traced to water (or frost) and not to the absence of a magic
expansion gasket.
Antennas on chimneys: We also find chimneys used as a mounting spot for antennas or other equipment. Chimneys are not intended to function as a support for other building components.
Mounting an antenna on a chimney may damage the chimney making it unsafe or causing building leaks. You're also inviting a lightning strike on your chimney by mounting equipment there.
A lightning strike on a chimney can cause severe damage to a home, including setting it on fire. Some readers have reported just that happening to their home. Sketch courtesy of Carson Dunlop.
Obstructed or Blocked Chimney Flues
Obstructed or Blocked Chimney Flues might be discovered by inspection and luck as shown here.
A hornets nest is partly blocking this flue. Not only may there be a chimney safety or performance
problem, there could be a problem for the inspector or the building occupants when the hornets
are disturbed.
A meticulous chimney mason would also criticize the mason who built this chimney
for leaving oozed mortar sticking into the flue between each pair of flue tile liners.
That detail
can make a chimney hard to clean and can make for damage and flue leaks if the mortar "ears" are
broken off during chimney cleaning.
We were able to take this clever photo of a dark chimney interior by using our Maglite™ flashlight along
with a Nikon Coolpix 4500™ camera on which we re-set the ISO or equivalent film speed to its
highest setting (800). This trick with a digital camera will sometimes let an inspector "see" into
a pretty dark area.
Angled Chimney Flue Tiles
Just as we reported that a clay tile lined chimney would be difficult to clean due to projecting concrete between vertically-stacked clay chimney tiles, clay tiles need to be cut properly when constructing an angled chimney such as the one shown in Carson Dunlop's sketch.
Only the bottom design, showing that the clay chimney tile was cut on an angle, is correct. The top two designs risk both cleaning difficulties and also water, smoke, soot,or creosote leaks into the chimney structure.
Determine the Extent of Chimney Damage and the Safety of the Entire Chimney Flue
First, you will want to be absolutely sure that the chimney damage, whether to the ceramic clay flue liner or to the surrounding masonry or both, is limited to the upper, visible, accessible part of the chimney.
Other chimney damage lower in the chimney itself as it passes through or alongside the building could be very dangerous, even fatal if carbon monoxide or other flue gases leak into the building or if sparks cause a fire.
We suggest that you hire a professional chimney sweep who can examine the entire flue. Most chimney sweeps also offer repair services, and can suggest what repairs are needed and give alternatives for the particular chimney and flue on your building.
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Additional technical contributors & reference sources for this article are listed below.
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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
"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
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.
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:
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
"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.
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