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This article describes chimney defects that can best be spotted and diagnosed by on-roof access. These include inspection of the chimney cap and crown or top seal, the condition of the uppermost chimney flue, the separation of multiple chimney flues. Additional rooftop chimney inspection details are provided in subsequent sections of this article. These articles on chimneys 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.
Watch out: at the same time, there are many rooftop defects, including potentially costly or dangerous problems, that cannot be discovered by a from-ground-level inspection, even using high powered binoculars. At left is an example: an improperly-constructed chimney flue and cap that risk leaks and hidden damage to the chimney flue. More examples of chimney flue damage are at Flue Tile Damage in Chimneys.
An on-roof inspection of the chimney allows inspecting the upper portion of the flue lining, cap and
roof flashing, chimney top seal or "crown", and it permits a closer inspection of masonry chimneys for cracking or other damage that might not be
visible from a more remote "from ground" inspection.
Summary of Inspection Points at Chimney Caps & Crowns
See CHIMNEY CAP & CROWN for details about chimney caps & crowns where we detail the various types of covers & terminations found at the top of chimneys and flues & their common defects. There we also cite pertinent chimney top cap / crown building codes & standards.
Rain Cap: a rain cover on top of a chimney flue designed to keep out rain (which can damage the flue or appliances it vents) and intended to reduce downdrafts in the chimney in windy conditions. The metal cover shown in our photo at left is a metal "rain cap".
This interesting chimney has a metal cap on one flue and not the other. The metal chimney cap looks home-made and perhaps not functional.
Chimney Cap: on a masonry chimney the chimney cap is a pre-cast concrete or poured in place concrete seal around the flue tile (on a modern masonry chimney). In our photo (above left) the chimney cap, also called a mortar cap, is the white concrete visible around the projecting flue tiles at the top of the chimney. Some of us call the mortar cap or concrete chimney cap the chimney crown. The Masonry Institute of America calls this the "chimney cap" - we're following their terminology.
The purpose of the chimney cap [chimney crown] is to close off the space between the
flue liner and chimney wall, to shed water clear of the chimney and generally prevent moisture entry.
The rain rain cap has the job of keeping rain and wind down-drafts out of the chimney. The rain cap or hood may also be charged with preventing sparks from leaving the chimney - a fire safety measure shown in Carson Dunlop's Sketch.
[Click to enlarge any image]
The Brick Institute of America (BIA) recommends chimney caps of pre cast or cast-in-
place concrete a minimum of 2-inch thick with a projection of 2 1/2-inch beyond the face of the masonry surround so that water shed from the top will not run down the face of the brick.
Chimney cap slope: The chimney "cap" [or crown] should slope away from the flue at a good rate of about 3-inches per foot.
The chimney cap should not be
bonded to the flue liner or top of the chimney in order to allow for thermal expansion of the liner. The space between the cap and the flue liner must be closed with a flexible sealant.
Mortar chimney "caps" are prone to cracks and allow water to drain over the face of the chimney masonry leading to spalling, loss of mortar
and leakage to the interior spaces. Corrosion at the chimney base cleanout doors are common to those types of chimneys.
Check the chimney top for damaged masonry (or rusted metal), a missing cap,
damaged, cracked, or missing top seal or crown on the top of a masonry flue, and here, an important discovery (at least in some jurisdictions) is whether or not
the chimney is single wythe or thicker masonry and whether or not the chimney has (or perhaps needs) a chimney liner.
Missing Chimney Rain Cap
If we want proof that people don't spend a lot of time looking at their chimney, ask a home inspector or chimney sweep how often they find that the rain cap or spark arresting chimney cap has been completely lost from a chimney.
As Carson Dunlop's sketch shows, a missing cap invites water damage to the chimney and the equipment it vents, draft problems, and unsafe operation.
Water entering the chimney can cause enough corrosion in a metal flue that the chimney needs replacement.
Chimney crown/cap damage or missing drip edge
In Carson dunlop Associates' sketch at left the chimney crown looks recently installed and does not drain past the chimney sides. There has been water damage covered up with painted metal on the chimney side facing us.This chimney needs some safety inspection and probably new caps on the flues.
As Carson Dunlop's sketch shows (left), a good drip edge at the chimney top cap helps reduce water and frost damage to the chimney sides and structure.
Watch out particularly for flat or even in-sloping metal caps on wood-framed chimney chases built around metal chimneys - these are often a source of hidden leaks into the structure and potentially dangerous rust or corrosion damage to fireplace inserts and flues as well as damage to heating equipment.
Carson Dunlop's sketch (left) shows some details of good chimney crown/cap construction. The object of these details is to avoid water and frost damage to the flue or to the chimney itself.
Chimney crown/cap history: if a chimney has spent part of its life with no rain cap installed,
or if the masonry cap is poorly constructed, 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, such as rust, formation of corrosive condensate,
Damaged Masonry Chimney Cap or Crown
Chimney Cap/crown: shown here is the concrete seal around the top of a chimney, sealing the upper chimney surface around the projecting chimney flue (clay flue tiles in this photo) in order to close off the space between the
flue liner and chimney wall, to shed water clear of the chimney and generally
prevent moisture entry.
Here is a chimney with a mortar cap but no rain cap. The design would have been better if one of the clay flue liners projected several inches higher than its neighbor, and if the concrete cap had been pre-cast or otherwise constructed to give an overhang past the sides of the chimney so that runoff would not wet and damage the brick masonry below.
Installation of this chimney cap would also have been better if there were an expansion gap and sealant permitting the flue tiles to expand without cracking the surrounding concrete cap.
See CHIMNEY CAP & CROWN for definitions of chimney rain cap, chimney cap, chimney crown, and for more examples of chimney top defects that may be visible from the ground or from an on-roof inspection.
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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: email@example.com
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 firstname.lastname@example.org
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
Residential Masonry Fireplace and Chimney Handbook, James E. Amrhein, S.E., MIA, Masonry Institute of America, 2d. Ed., 1995, ISBN 0-940116-29-4. The MIA is in Los Angeles, CA 213-388-0472. This manual reflects the 1994 Uniform Building Code, Energy Conservation Requirements of California, and the U.S. Department of Housing and Urban Development - HUD. The complete UBC is available from the International Conference of Building Officials (ICBO), Whittier CA 310-699-0541.
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.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
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. Also 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.
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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Carson Dunlop, Associates, Toronto, have provided us with (and we recommend) Carson Dunlop Weldon & Associates' Technical Reference Guide to manufacturer's model and serial number information for heating and cooling equipment 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.