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ODORS GASES SMELLS, DIAGNOSIS & CURE
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STAIN DIAGNOSIS on BUILDING EXTERIORS
WOOD, COAL STOVES & FIREPLACES
WOOD STOVE SAFETY
Chimney leaning, cracking movement: diagnosing ongoing chimney movement: 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.
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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.
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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 left we see a wide metal strip which has been fabricated to cover the gap that has opened between the chimney and the building.
The chimney movement photographs presented here shows metal strapping used in a questionable attempt to stabilize the chimney by bolting it to the house gable-end wall. You can see steel chimney straping in the photos at above left and center.
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 CHIMNEY LEANING, REPAIR OPTIONSCarson 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.
[Click to enlarge any image]
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.
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 above left, courtesy of Arlene Puentesshows 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.
Green link shows where you are in this article series.
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