Water Leaks & Frost Damage to Chimneys & Flues
Where do chimney leaks occur, how are they fixed?
CHIMNEY DAMAGE by LEAKS & FROST - CONTENTS: How water and moisture leak into and damage chimneys and heating appliances. Chimney inspection, diagnosis, and repair for water or frost damaged chimneys and flues.
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Water damage to chimneys & flues:
This article describes water leaks and moisture that damage masonry and metal chimneys and the heating appliances that are connected to them. We list the common sources of water and leaks and we include warnings for inspectors who need to examine equipment as well as the chimney itself when water or moisture leaks are detected.
Our photo (page top) shows water pouring into a basement, coming out of the chimney cleanout during a heavy rainstorm. Readers of this article should also see CHIMNEY COLLAPSE RISKS, REPAIRS.
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.
Our photograph at left shows a stunning waterfall flowing out of a "sealed" chimney cleanout in a basement. Lots of roof spillage or surface runoff was entering the base of this chimney.
[Click to enlarge any image]
Moisture is the major cause of chimney corrosion and disintegration in
both masonry and metal chimneys. The flue gases are acidic in nature and if
allowed to condense and saturate the masonry or joints in metal flues the
destructive results will soon be apparent.
Mechanical problems in the
construction or settlement after construction and over firing or flue fires will also
contribute to the problems.
External moisture enters the chimney through cracked caps, porous
masonry, poor mortar joints and improperly designed and installed roof flashings.
Internal moisture (condensation) collects in cracked or separated flue tiles,
blocked flues and chimney caps.
Masonry chimneys subjected to moisture damage can have efflorescent
salt stains, spalled bricks, eroded mortar joints, flaked cracks in the ceramic flue
liner and cracked caps.
Metal components of a vent system can have rust and white acid stains at
joints, corrosion holes along the bottom of horizontal connectors and corroded
chimney cleanout doors at the base of the flue.
Moisture enters a chimney structure from several locations:
Missing chimney cap lets wind blown rain and snow enter the flue
Damaged chimney crown lets water enter the chimney structure
Leaks at the chimney sides let wind-blown rain enter the chimney structure
Leaks at chimney flashing let water enter the chimney structure
Ground and surface runoff or roof spillage by a building often enter the base of a chimney that extends below ground.
Water leaks into a Chimney can Damage the Chimney and the Appliances Connected to It
The result of leaks into a chimney can be unsafe heating equipment as well as costly damage to the chimney, the appliances connected to it, and to the building itself.
Frost or water damage can crack or break a masonry clay chimney tile resulting in fire or flue gas hazards at the building
Broken chimney flue liner parts can obstruct the chimney flue resulting in dangerous, potentially fatal carbon monoxide gas hazards
Water entering the heating appliance such as a furnace, boiler, water heater or woodstove can cause rust damage to the heater components or can damage electrical controls on the appliance, leading to costly repairs
Water entering a wood-framed chimney chase can also invite insects, rot, or mold problems in the building
Water entering a metal chimney or flue can cause corrosion or rust which perforate the chimney or flue vent connector leading to equipment failure, improper operation, and dangerous flue gas leaks in the building.
Even a stainless steel manufactured chimney is not immune to rust and corrosion when it faces the combination of water in the flue interior (or between the layers of metal of a multi-wall chimney) and corrosive acids that form as soot and creosote are dissolved by the water in the flue.
Where do Most Leaks Occur at Chimneys?
Question: We can't find the leak in our chimney
2017/09/10 Laura said:
Our chemney leaks every time it rains heavy.
We have had a builder and roofer out over thelast two years who have made various changes (or they told us they have), however its stil dripping and letting rain water in. Any ideas?
Sketch above / left showing improper slope on the masonry cap of a chimney and also the omission of a rain cap atop the chimney flue and our chimney drawing below were provided by Carson Dunlop Associates, a Toronto home inspection, report writing & education firm.
Reply: where to look for leaks on or around chimneys
It sounds as if the people working on the problem have tried solutions without finding the actual leak source.
I'd start by trying to find, more accurately, just where water is coming in to the building:
is it a roof flashing problem (leaks where a chimney passes through the roof) ,
a chimney rain-cap or top seal problem (water enters at or near the top of the chimney),
a chimney body problem (water enters somewhere along the route of the chimney parts that are exposed outside), or a
groundwater problem - water enters at the chimney base or from ground level or below, or less common,
an internal leak into a chimney (from a nearby leaky supply or drain pipe).
You might get a more clear understanding of the leak by asking for an inspection by a chimney sweep who's certified (National Chimney Sweeps Guild) and who can examine both the entire exterior and the entire flue interior of the chimney to see where water is originating.
I suggest preparing yourself by reading over some of the chimney leak diagnosis and repair articles I'll give below, to become familiar with the different types of leaks that occur in or on or around chimneys.
Note that some of these leak problems occur only on brick or other masonry chimneys while others like CHIMNEY CHASE CONSTRUCTION will discuss leak points that only occur around the top of a wood-framed and enclosed metal chimney.
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Questions & answers or comments about how to spot water or frost damage to chimneys & how that chimney damage may be repaired.
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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: firstname.lastname@example.org
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 email@example.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 #211-3.1 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.php. 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 Building & Environmental 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.
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
Carson, Dunlop & Associates Ltd., 120 Carlton Street Suite 407, Toronto ON M5A 4K2. Tel: (416) 964-9415 1-800-268-7070 Email: firstname.lastname@example.org. 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 extensive home inspection education and report writing material.
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.
TECHNICAL REFERENCE GUIDE to manufacturer's model and serial number information for heating and cooling equipment, useful for determining the age of heating boilers, furnaces, water heaters is provided by Carson Dunlop, Associates, Toronto - Carson Dunlop Weldon & Associates 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.
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.
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 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