Photograph of a curved chimney separating from a building, viewed from outside. Outdoor Chimney Inspection, from the Ground
Ground-level detection of Leaning Moving or Separating Chimneys on buildings

  • CHIMNEY LEANING, SEPARATION, MOVEMENT: OUTDOORS - CONTENTS: Ground-level chimney inspections: curved, collapsing chimneys. Evidence of chimney foundation defects. Leaning, separated or cracked chimneys; missing chimney supports. Collapsing metal chimneys. How to detect chimney movement. What causes chimney movement or collapse
    • Other chimney defects & hazards visible by outdoor ground-level inspection
    • Overgrown chimneys & flues - trim back vegetation
    • Bird or other animal nests in or on chimneys - fire & gas hazards
  • POST a QUESTION or READ FAQs about how to inspect chimneys from outdoors at ground level

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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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Chimney Inspection Procedures - Starting Outdoors

Components of a masonry chimney (C) Carson Dunlop Associates

Here is a list of some (not all) common chimney defects visible from a more distant view, perhaps at ground level. Later we detail chimney defects that can best be observed from roof-level access.

[Click to enlarge any image]

  • Chimney movement: leaning, settling, bending, breaking, cracks, curving separation from the building, bad footing;
  • Chimney height: too short, inadequate clearance above roof; Chimney height too tall without bracing; see Required Chimney Height
  • Chimney exterior cracked, spalled, loose masonry components (bricks, blocks) or loose, missing mortar
  • Chimney leaks: water leaking into the chimney interior or structure, such as efflorescence, frost cracking, spalling
  • Chimney cap missing, chimney cap not draining; wrong type of cap for flue type or items being vented
  • Chimney crown cracked, damaged, missing, leaking, or not properly sloped to drain off of the chimney top; no drip edge over chimney sides. Some experts including Al Carson call our "crown" the chimney cap. Sketch above showing the basic parts of a masonry chimney is courtesy of Carson Dunlop.
  • Chimney type & usage: chimneys improperly shared among appliances, building rooms or building floors, or chimneys of the wrong type in use.

We describe these and other chimney defects in detail in the following sections of this article.

Chimney Separation from House, Settlement, Leaning, Movement, Cracking

A chimney which has settled and moved away from the building is almost certainly a serious safety hazard risking fire and flue gas leaks into the structure, and it is likely to require costly repairs or complete reconstruction. Details of how to see and evaluate chimney movement and separation are provided here.

Foundation Support for Masonry Chimneys

A summary of the chimney footing problem is just below.

What happens if a chimney footing is missing or inadequate? 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.

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.

Chimney with no footing (C) Daniel FriedmanEven 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.

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.

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.

Other Chimney Defects Visible by Outdoor Ground-Level Inspection

Overgrown chimneys & flues - trim back vegetation

Chimney overgrown at top - fire hazard (C) Daniel FriedmanChimney completely overgrown with vines is a fire and carbon monoxide hazard (C) Daniel Friedman

Watch out: As you can certainly see from our photos above, tree, shrubbery or vine growth close to or covering a chimney can be a serious or even fatal hazard including risk of

  • Fatal carbon monoxide poisoning of the building occupants - venting a gas appliance into a chimney that is blocked by over-growth or blocked by anything else is likely to both cause production of high levels of carbon monoxide (especially from gas fired heating equipment) and to cause the fatal venting of carbon monoxide back into the building.
  • House fire - when chimney sparks ignite dried vegetation
  • Chimney structural damage as vine growth holds moisture on or in the chimney surfaces

Bird or other animal nests in or on chimneys - fire & gas hazards

Chimney with no footing (C) Daniel Friedman

As you can certainly see from our photo (left), this chimney, located in Rabat, Morocco, serves as a home for a stork's nest. This chimney top is essentially totally blocked by highly-combustible material - a bird's nest.

Watch out: even in areas where storks are not common, other smaller birds, squirrels, and some other animals may make a smaller nest inside the chimney or its flue, presenting hazards of blocked flue, fire, and potentially fatal carbon monoxide poisoning.

Risk of Hidden Chimney Damage - hybrid structures

This next chimney shown at below left ... well we're not sure what the heck we've got here.

We see a fired clay masonry flue tile projecting through a flat, leaky, too small, metal chimney cap surrounded by a wood and plywood structure.

We suspected that this was a masonry chimney that had suffered frost damage.

Wood cover on masonry chimney - unsafe (C) Daniel FriedmanThe owner installed a new clay flue tile at the very chimney top and boxed in the masonry chimney to cover the frost-damaged chimney structure (the home was being sold).

We've got a few concerns:

  • a missing rain cap - risking hidden damage to flue, flue vent connectors, heating equipment below
  • a defective leaky chimney cap or crown risking hidden damage to the chimney itself
  • wood framed covering over a chimney of uncertain material and condition, possibly adding to the fire hazard
  • a risk of hidden damage, unsafe flue, fire hazards, flue gas leak hazards

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.

Collapsing metalbestos chimney (C) Daniel Friedman


Poorly-secured or poorly-supported factory-built chimneys risk collapse

As you can certainly see from our photo (left), this chimney is collapsing and is unsafe.

More about this chimney is found at BRACING for METAL CHIMNEYS.

After reviewing this "ground level chimney inspection guide" readers should then review CHIMNEY INSPECTION at ROOFTOP which describes chimney defects which may be difficult or impossible to detect from a ground-level inspection.

Readers interested in the outdoor portion of chimney inspections should review   FOUNDATION SUPPORT for CHIMNEYS (below in this article) followed by the next article: CHIMNEY LEANING, SEPARATION, MOVEMENT and also CHIMNEY COLLAPSE RISKS, REPAIRS.

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