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Blog by Evergreen Home Inspection

Chimney flues and the interiors of chimneys

In my opinion, this may be the most important exclusion from the home inspection. The fact is, home inspectors are required to look at the exterior of chimneys and the venting of heating systems and other combustion ‘appliances’. The internal portions of the chimney (what is called the ‘flues’) are very often partially or completely concealed and are thereby listed as excluded items in the Standards of Practice that govern home inspections. To fully inspect the inside of the chimney one needs to have the right equipment, remove combustion appliances (woodstoves, heating systems, water heaters, etc.), clean the chimney, and view the concealed areas (typically with a camera). Home inspectors look at the chimney – but they can’t inspect them fully.

Most inspectors (at least in my region) recommend having what is called a Level 2 chimney inspection performed by a qualified chimney sweep. This utilizes specialized cameras that do a video scan of the entire chimney interior. This is most critical for older chimneys, chimneys serving woodstoves, chimneys where you can’t see any of the flues from below, or any chimney with evidence of significant structural distress. Level 2 inspections can be expensive to do – but not as expensive as finding the problems after you move in.

What you need to realize is that chimneys and fireplaces are just rife with problems. And while this may be especially true with older homes a lot of relatively new chimneys also have problems. A few conditions that home inspectors commonly find include:

  • No flue liners. Unlined chimneys were the norm up into the 20th century. Lots of unlined flues are still in use. Many are still functional but all are suspect as they will often deteriorate when there is a change of use with the chimney (for instance, converting from oil to gas). Very often they will require upgrading by your municipality or utility company when the heating or hot water systems are replaced. Even if not required upgrading is normally desirable.
  • Deteriorated terracotta liners. The clay liners commonly used for the last 80 years routinely crack and fail. Or, the mortar between the sections falls out. Or, they were improperly installed. Or, movement in the chimney causes these the liners to shift. Or, when exposed to the combustion by-products of gas systems, they simply fall apart. They don't work well for wood stoves and can be problematic for gas-fired systems. I have to say that a lot of terracotta flues look (and are) fine when the chimney was well built and the flues serve seldom used fireplaces or oil –fired heating systems. But they are also prone to cracks and distress.
  • Concealed faults in the installations. Sometimes wood was left as forming under the fireplace or elsewhere. Poor clearances to combustibles are common. Gaps were left around the damper frame. Older, less safe flue installations may or may not be functional – but all will require repairs and upgrading with any change to the system.
  • Dampers often are missing, do not work, work poorly, or are very loose-fitting, allowing continual heat losses.
  • The metal flues used in manufactured fireplaces (what used to be called ‘zero clearance types’), while very often okay, also have been a source of numerous fires.

I could go on, but chimney flues may have serious problems that simply are not visible to a home inspector. The cost of repairs to flues, moreover, can run into the tens of thousands of dollars.

A lot of buyers remark that they will have the chimney cleaned and inspected before they use it. Great – but if the chimney sweep identifies problems that may cost thousands of dollars to fix, would you rather hear about this after you own the home – or before, when the issues may still be subject to negotiation. Also, it is good when a homeowner says that they have had the chimney cleaned – but this doesn’t mean they had a full inspection done.

(Just to be fair: most of the metal type B vents used on older and mid-efficiency gas systems do not show problems; the same for most of the PVC plastic pipe used for venting high efficiency gas systems. Many lined flues serving oil systems are also at lower risk).