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CHIMNEY INSPECTION DIAGNOSIS REPAIR
BACKDRAFTING HEATING EQUIPMENT
CARBON MONOXIDE - CO
CHIMNEY CAP & CROWN
CHIMNEY CLEANING PROCEDURES
CHIMNEY COMPONENT DEFINITIONS
CHIMNEY CRACK DETECTION & DIAGNOSIS
CHIMNEY DRAFT & PERFORMANCE
CHIMNEY FIRE ACTION / PREVENTION
CHIMNEY HEIGHT & CLEARANCE CODE
CHIMNEY INSPECTION, FLUE INTERIOR
CHIMNEY LEANING, SEPARATION, MOVEMENT
CHIMNEY REPAIR METHODS
CHIMNEY STAINS & LEAKS
CHIMNEY TYPES & MATERIALS
DIRECT VENTS / SIDE WALL VENTS
DRAFT REGULATOR, DAMPER, BOOSTER
FIRE CLEARANCES INDOORS
FIREPLACES & HEARTHS
FLUE VENT CONNECTORS
MASONRY CHIMNEY GUIDE
METAL CHIMNEYS & FLUES
SAFETY RECALLS CHIMNEYS VENTS HEATERS
SOOT AT CHIMNEY TOP
STAIN DIAGNOSIS on BUILDING EXTERIORS
WOOD, COAL STOVES & FIREPLACES
This article describes chimney inspection procedures and critical chimney defects which can be observed from outdoors at ground level. We begin with the detection of chimney movement, its causes, its symptoms. These articles continue with other chimney defects that can be found by visual inspection from outdoors at ground level, then from an on-roof inspection, followed by indoor inspections and ending with chimney-flue interior inspections.
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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.
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.
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.
[Click to enlarge any image]
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.
We provide a series of articles on diagnosing chimney cracks and movement include Chimney Movement - Causes, then CHIMNEY MOVEMENT, ONGOING vs STATIC where we describe determining whether chimney movement is ongoing. Readers diagnosing chimney movement and foundation problems should also see CHIMNEY LEANING, SEPARATION, MOVEMENT: OUTDOORS, and CHIMNEY LEANING, SEPARATION, MOVEMENT Chimney Crack & Collapse Risks. Repairs for moving chimneys are discussed at CHIMNEY LEANING, REPAIR OPTIONS.
A Catalog of the Causes of Chimney Movement
Carson Dunlop's sketch shows a number of common causes of chimney movement. Understanding the cause of movement informs the choice of repair methods. Three of these have to do with the chimney footing:
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.
See CURVED BRICK CHIMNEYS, SULPHATION for a description of apparent chimney movement caused by the combination of a missing flue liner and sulphation.
Both outdoors and indoors we may also see chimney cracks which could be due to chimney movement (introduced above) or due to compression loads or other chimney construction problems (just below).Cracked concrete block chimneys: Our photo at left shows dangerous cracking indoors in a concrete block chimney used to vent a heating appliance. (You might also notice that the barometric damper is not level - a much simpler problem to correct.) As a chimney leans away from the house we might find several problems:
Also see CHIMNEY CRACK DETECTION & DIAGNOSIS
The usual repair is to remove and replace the chimney, though in some cases it may be possible to re-line a chimney and to jack an intact masonry chimney back to level and repair its connections into the building.
Goofy Moving Chimney Repairs and Attempts to Hide Chimney Movement
Attempts to hide chimney movement can be dangerous since if there is a safety problem the building owner or inspector may not pick up its clues.
The fresh and thick band of caulk between the chimney and the wall as shown in this photograph were traced to a chimney separation that had been "repaired" simply by more caulking at the wall.
Because caulk is flexible, if it has been recently applied caulking may hide an ongoing chimney movement problem. But even if the chimney is no longer moving (or we think it is not moving) an inspection for flue safety and fireplace safety are essential.
In the next article in this series, Ongoing Chimney Movement, we provide a detailed example of a chimney which probably moved continually over many years, and which produced a wide gap between the chimney side and the building.
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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Frequently Asked Questions (FAQs) about Chimney Movement Causes, Diagnosis, & Evaluation
Question: chimney damage or movement caused by chimney sweep work?
I had a chimney sweep on my roof last week He cut the top off one of the clay liners to accommodate a chimney cap. After his departure I noticed the top of the chimney was moved away from the house about 1 inch. Could the chimney sweep leaning on the chimney produce enough force to move the chimney? I am absolutely sure the chimney was not away from the house prior to his work. Thanks for any help you may provide. - M.H., Woburn MA
Reply: check the chimney flue for safety ASAP
A competent onsite inspection by an expert usually finds additional clues that help accurately diagnose a problem such as the chimney movement you describe. And while I express opinions and give advice below, we're talking email here - not a substitute for an onsite expert. An unsafe chimney (yours, if it moved, may be unsafe) is a fire and carbon monoxide hazard risking fire or even a fatality. Sorry to sound so "scary" but when we're talking about chimneys by email I feel obligated to worry about safety first.
That said, here are some things to consider:
Watch out: your first priority is safety: Assuming that your chimney is in use, perhaps by your heating system or a fireplace, the first priority is to make sure that the chimney is safe to use. Do not delay in resolving that question. I offer "how to" advice in these notes.
Any chimney of any type that has moved raises very important safety questions.
I would like to see sharp photos of the chimney cap installation, the chimney from roof and from ground, of any scraps you find, any cracks you observe, and I can offer further comment - but an onsite inspection by an expert is most important rather than my email views.
Finally, your chimney inspector might want to be familiar with NFPA 921 - if s/he is someone who is a professional and who works with fire and explosion investigations they probably know this "Guide for Fire and Explosion INvestigations". The current edition of NFPA 921 can be purchased online at NFPA 921: Guide for Fire and Explosion Investigations (Amazon) or directly from the NFPA at nfpa.org/aboutthecodes/AboutTheCodes.asp?DocNum=921&cookie_test=1 - listed at our references as well: 
Questions & answers or comments about the causes of chimney separation from the building, cracking, leaning, or other chimney movement problems.
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