Plaster finish cracking on masonry chimneys

Plaster finish cracking on an older chimney could indicate that the chimney is no longer structurally sound. Unsound chimneys are dangerous, particularly in an earthquake. If still being used for an open fire there is the potential fire risk as well. Engaging a chartered professional engineer to assess and advise on options to restrain, strengthen, demolish or rebuild the chimney is recommended.

Causes

The building or chimney has settled

Earthquake damage

The chimney is not adequately tied to the structure

Listed under: masonry, plaster and fibrous plaster, earthquakes, Roof, chimneys and flues and fireplaces

Cause

The building or chimney has settled

Repair

  • if the preference is to keep the chimney, follow the engineer’s advice for strengthening or rebuilding

  • removal of a structurally unsound chimney does not require a building consent (but work must still comply with the Building Code). This exemption is limited to any building up to 3 storeys high as long as the removal does not affect the primary structure, any specified system or any fire separation (which includes firewalls protecting other property) Remember to check roof sarking/framing which sometimes is supported on chimney structures. Be aware also that some bracing walls rely on support from chimneys either side

  • any repair work that is necessary – for example, making good the gaps left in a roof after chimney removal – can also be done without a consent

  • you should only attempt these repairs yourself if you have the skills, knowledge, experience and tools to complete the job properly. Poor quality work on the building exterior can result in leaks and other problems and may affect your house insurance cover

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Cause

Earthquake damage

Repair

  • as above

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Cause

The chimney is not adequately tied to the structure

Repair

  • a chimney not adequately tried to the structure is dangerous. Engaging a chartered professional engineer to assess this chimney is strongly recommended

  • removal of a structurally unsound chimney does not require a building consent (but work must still comply with the Building Code). This exemption is limited to any building up to 3 storeys high as long as the removal does not affect the primary structure, any specified system or any fire separation (which includes firewalls protecting other property) Remember to check roof sarking/framing which sometimes is supported on chimney structures. Be aware also that some bracing walls rely on support from chimneys either side

  • any repair work that is necessary – for example, making good the gaps left in a roof after chimney removal – can also be done without a consent

  • you should only attempt these repairs yourself if you have the skills, knowledge, experience and tools to complete the job properly. Poor quality work on the building exterior can result in leaks and other problems and may affect your house insurance cover

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