Chimney moving at roof (C) Daniel Friedman Repair Methods for Ongoing Chimney Movement, Leaning Chimneys
     


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How to fix chimney separation or movement: this article describes the common repair methods used to handle a chimney which is leaning, cracked, or separating 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.

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How do We Repair Ongoing Chimney Movement?

Chimney separation at house (C) D Friedman A Puentes

 

As we cited earlier at Chimney Movement is Ongoing - Evidence, 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 at the top of this page 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.

In both photos below, a wide metal strip has been fabricated to cover the gap that has opened between the chimney and the building (below right) and a heavy metal strap has attempted to "bolt" the chimney to the home (below left, also visible at the upper chimney section (below right).

[Click to enlarge any image]

Just below are additional photographs of a masonry chimney with significant separation and leaning away from the building.


Chimney moving at roof (C) Daniel Friedman Chimney moving at roof (C) Daniel Friedman

Why is this chimney strapping repair alone probably inadequate?

  1. If the chimney is settling because of an inadequate footing, it is unlikely that this repair will succeed. On occasion we've seen the mass of a heavy chimney actually pull the building wall along with it as it settled and tipped further.
  2. The chimney flue interior is likely to be damaged and unsafe
  3. The fireplace box, hearth, and support are likely to be damaged and unsafe

What could have been done to repair the chimney shown above?

  1. Confirm that the defect is due to a bad chimney footing, stabilize the footing using slab-jacking or helical piers
  2. Re-line the damaged chimney flue
  3. Align, stabilize, and repair cracks in the fireplace box and hearth

Alternatively

  1. Remove the chimney entirely, then construct a new chimney on a proper footing
  2. Abandon the chimney entirely, stabilize and leave it in place, provide alternative chimneys to vent the home heating appliances using a manufactured chimney elsewhere on the building
  3. Abandon the chimney entirely, convert the heating boiler or furnace to a high-efficiency direct-vent unit.

Which of these alternatives makes most sense depends on other factors such as the condition of the heating equipment and the desire to have a traditional masonry fireplace.

A Summary of Leaning Chimney Repair Methods

Strapping a masonry chimney to the building in an attempt to stabilize a tipping or leaning chimney it is unlikely to work, especially if the root cause of chimney movement is an inadequate or tipping chimney foundation. The total weight or mass of a masonry chimney is enormous.

Trying to hold this weight in place by strapping the flue to the building structure risks bending or moving the structural wall in many instances. (If a chimney has a sound footing or a soundly-repaired footing and is to be tied to the building as a retrofit repair, the building tie-in may need to pass through the building rather than just being connected to the building wall abutting the chimney.)

It is normal to tie a masonry chimney to the building to prevent movement. Those ties, if present, are likely to be hidden between the chimney side facing the building and the building wall itself. That lateral chimney support stabilizes a chimney that has a sound footing. But lateral support cannot normally stabilize a chimney whose footing is missing or tipping.

Also See Bracing & Support for Chimneys.

Chimney reconstruction: if the chimney has moved more than a very small amount, perhaps less than 3/16", some chimney repair companies may suggest that the chimney should be disassembled and rebuilt correctly. That is because they are worried that internal cracks in the masonry flue have made the chimney a flue gas and fire hazard.

Certainly if a chimney has moved significantly away from a building it is almost certainly dangerous, risking a building fire and flue gas leakage.

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.

Chimney top repairs: if the damage to a chimney top or flue is confined to the area from the roof surface up to the chimney top, it is common to remove and rebuild the chimney in that location. Make sure that the new chimney top has a proper chimney cap and rain cap as well as an expansion joint/seal around the masonry flue at the chimney cap. See CHIMNEY REPAIRS, TOP & CLAY FLUE TILE for details.

Chimney foundation repairs: If a leaning chimney is relatively un-damaged, and if the movement is traced to ongoing chimney foundation settlement, it might be possible to use helical piers, driven pins, or other foundation repair methods to repair the chimney.

Flue relining a moving chimney: Some chimney repair companies may suggest stabilizing a chimney flue that has moved, followed by installation of a flue liner in order to assure that the flue is fire and gas safe. See Re-Lining Choices for Masonry Chimneys.

Fireplace movement repairs: If you are considering this repair be sure that your mason and chimney company inspect any fireplaces carefully. we have observed movement and cracking in the firebox which made the fireplace and hearth serious fire hazards themselves, independent of questions about the safety of the chimney flue. We have observed fireplace hearth settlement repairs obtained by jacking the settled hearth from below, combined with careful inspection and sealing.

If the fireplace itself has settled or tipped, typically also causing chimney separation, it may be possible to add support and jack the fireplace base level using slab jacking or foundation settlement repair methods. However the risk of this approach is leaving a damaged and unsafe fireplace or chimney flue in place. Very thorough and expert inspection is required and chimney relining may also be needed. The cost of all of those steps may be competitive with reconstruction of the fireplace and chimney. See Fireplace Safety Hazards.

Metal chimney repairs: if the chimney is a factory built or metal chimney and flue, most often the proper repair is complete replacement of damaged or rusted chimney parts. An exception, of course, is the replacement of a damaged or missing chimney rain cap or above-roof components. See REPLACEMENT PARTS for METAL CHIMNEYS for details.

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