Chimneys get attention when they smoke and are otherwise ignored. That is unfortunate, because they carry three distinct risks and only one of them announces itself.
Creosote and fire risk
Burning wood deposits creosote inside the flue. It accumulates, and it is flammable. A chimney fire in a heavily deposited flue burns extremely hot and can spread into the structure.
Regular inspection and cleaning where wood is burned is the control, and how often depends on how much you burn and what you burn. Damp or unseasoned wood produces considerably more deposit, which is a genuine consideration in Western Washington where keeping firewood dry takes effort.
If you use the fireplace regularly, treat inspection as routine rather than reactive.
The roof leak nobody attributes to the chimney
Chimneys are one of the most common sources of roof leaks, because a chimney is a large penetration through the roof plane and the flashing around it is complex.
Chimney flashing involves multiple components working together, and it deteriorates. Failed sealant, lifted flashing, and deteriorated mortar at the crown all let water in.
Leaks around a chimney frequently present some distance away, because water runs along framing before appearing. A stain that seems unrelated to the chimney may not be.
The chimney crown — the concrete or mortar cap at the top — is a common failure point and easy to overlook because nobody sees it.
Masonry chimneys and earthquakes
A recognised vulnerability in Washington. Unreinforced masonry chimneys on older homes can fail in an earthquake, and they are heavy objects positioned above living space and roofs.
This is worth including in any seismic conversation. Options range from bracing to removing the masonry above the roofline where the chimney is no longer used for its original purpose.
If you are considering seismic retrofit generally, ask about the chimney at the same time rather than treating it separately.
Freeze-thaw east of the Cascades
Masonry chimneys in Spokane, Yakima and the Tri-Cities take freeze-thaw damage that Western Washington chimneys largely avoid. Water enters mortar joints and small cracks, freezes, expands and widens them over successive winters.
Spalling brick — where the face flakes away — and deteriorating mortar joints are the visible result, and both accelerate once started.
Unused chimneys
Many Washington homes have chimneys that no longer serve anything, following conversion to other heating.
These still need attention. They are still a penetration through the roof, still a potential leak path, still a masonry mass in an earthquake, and if uncapped, still an entry point for water and animals.
Capping an unused flue is worth doing. Removing masonry above the roofline is worth considering where it is no longer needed.
Gas appliances
Gas fireplaces and inserts have their own venting requirements and their own maintenance needs. They do not produce creosote, but venting integrity matters for carbon monoxide reasons.
Working carbon monoxide detectors are essential in any home with gas appliances, and their manufacture date matters as much as their batteries — detectors expire regardless of battery condition.
What to look at
From the ground with binoculars: the crown, the mortar joints, any leaning, the flashing where it meets the roof, and the cap. From inside: any staining on the ceiling or wall near the chimney, any smell, and whether the damper operates.