How to detect evidence of ongoing or continuing chimney movement and separation from a building
Leaning, separated or cracked chimneys; missing chimney supports
Questions & answers about the cause, diagnosis, and repair of leaning, cracking, bending chimneys: chimney movement
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This article describes chimney inspection procedures and critical chimney defects which can be observed from outdoors at ground level such as defective or missing chimney footing and evidence of continuing or ongoing chimney separation and movement away from a building. We outline common repair methods used to stabilize loose or leaning chimneys.
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. As with most inspection and safety topics, this material may be incomplete.
How to Detect Evidence of Ongoing Chimney Movement
Sometimes
we see a chimney that has been "repaired" in this manner several times, with several
generations of concrete or caulk or wood trim strips.
Our closeup photo above showed a wide concrete patch between a chimney and the building. Often we see thick build-up of roofing mastic where a chimney has moved at the edge of a building roof.
Our photo at left shows what looks like at least three generations of repair attempts at this chimney and four generations of chimney movement.
From left: white caulk, solid mortar mix, gray caulk. The open gap of about 1/2 inch shows serious continuing chimney movement.
This chimney is unsafe.
Our photos just below show clear evidence of major and recurrent chimney movement. At left we see a build-up of roof cement where the chimney penetrates the roof structure.
At below right we see a wide metal strip which has been fabricated to cover the gap that has opened between the chimney and the building.
The third chimney movement photograph presented here metal strapping used in a questionable attempt to stabilize the chimney by bolting it to the house gable-end wall.
You can see another strap in the photo at above right.
A chimney with this much movement as well as any chimney with recurring movement almost certainly had an inadequate foundation or footing to start with. Strapping the chimney to the building is not going to work, the chimney is unsafe, and it probably needs to be torn down and replaced.
In some cases, however, if a chimney is intact it might be stabilized by any of several foundation jacking methods. We discuss this later at Leaning Chimney Repair Methods
Carson Dunlop's sketch shows six common causes of chimney movement. Understanding the cause of movement informs the choice of repair methods.
Other chimney movement gaps include caulk or even wood or metal flashing covering the gap between the chimney and the building. If the chimney has recently moved, say since the last "repair" you will see a new gap or you may see a line on the chimney where a sealant that used to touch the building has torn away from the building but remained attached to the chimney side.
Such chimneys are unlikely to be safe, probably need major repairs, and are likely to need to be replaced entirely.
If we see a leaning or moving chimney that already has
been re-lined we speculate that it may have been inspected and repaired but we'd still want
to know just what was done. If the chimney moved further after the liner was installed,
connections between vented appliances or a woodstove and the chimney flue liner could
have opened and thus might be unsafe.
Detecting a Missing or Inadequate Footing Support for Chimneys
What happens if a chimney footing is missing or inadequate?
As we discussed earlier when looking at outdoor clues of chimney movement, masonry chimneys represent a heavy concentrated load on the soil or
support structure. Therefore, proper footing support is critical and is generally
separated from the building footings except possibly at the exterior wall.
Our photo at left shows a diagonal, though nearly vertical, crack in a concrete block chimney. You should suspect that this chimney was built with an inadequate footing.
Splits in a chimney like this are very dangerous, risking flue gas leaks and fires. In extreme cases there is real risk of chimney collapse, as we discuss at Chimney Crack & Collapse Risks
It should not come as a surprise that some masonry chimneys are constructed with an inadequate footing, or no supporting footing whatsoever. Future settlement, movement, tipping, or separation of the chimney from the building is certainly likely in such installations.
Even a casual inspection from outside would raise the question about the absence of a footing for the chimney shown in our photo. You will notice the erosion of soil from below a little concrete skirt around the chimney base of this concrete block chimney.
On occasion you may find that the chimney was built on bedrock, taking advantage of a natural footing. Inspecting in a crawl space or basement where the bedrock is visible may reduce the anxiety of the inspector in such cases.
Homes built upon dry-laid stone foundations may have a chimney installed with its base sitting atop the foundation wall itself. Those chimneys might be stable, but be sure to review our warnings about dead end flues that are usually in use where such chimneys were built with no extension very far below ground level.
The photo at left, courtesy of Arlene Puentes shows significant chimney separation from the building. Significant and costly repairs are needed to correct this dangerous condition.
A tipping chimney footing appeared to be the underlying cause of this significant and dangerous chimney movement.
We continue below with an explanation of the causes of chimney movement, followed by a demonstration of how we spot evidence that chimney movement has been ongoing. Other articles in this series outline most other chimney defects that can be found outdoors or indoors on buildings.
At Chimney Movement Causes we explain the common causes of chimney cracking, separation, leaning, tipping, or collapse.
At Chimney Movement - Ongoing vs Static we continue this article with a case reporting evidence of ongoing chimney movement, repeated repairs, and the need to remove and rebuild a large masonry chimney.
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Additional technical contributors & reference sources for this article are listed below.
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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
"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 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.
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 - 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 - 3-4 - 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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