What Is a Chimney Liner and Do You Need to Replace Yours?

If your home was built before 1980, there's a good chance it still has its original chimney liner. In the northwest Chicago suburbs — where much of the housing stock dates from the 1950s through the 1980s — original clay-tile liners are extremely common. Some of these liners are now 50, 60, or even 70 years old. The question is: are they still safe?

What Does a Chimney Liner Do?

The chimney liner (also called the flue liner) is the interior channel that carries combustion gases from your appliance to the outside. It serves three critical functions:

• Containment: It keeps combustion gases — including carbon monoxide — inside the flue and out of your living space
• Protection: It protects the surrounding masonry from the heat and corrosive byproducts of combustion
• Draft: It provides the correctly sized channel for proper draft, ensuring gases move up and out rather than back-drafting into your home

The Three Types of Chimney Liners

Clay Tile

Clay tile liners are the most common type in older homes. They're installed in sections (typically 2-foot lengths) during chimney construction. Clay tile is durable and handles high temperatures well, but it's brittle — it can crack from thermal shock (a sudden chimney fire), freeze-thaw cycles, or the acidic condensate produced by gas appliances. Once cracked, clay tile cannot be repaired; the liner must be relined.

Stainless Steel

Stainless steel liners are the most common relining solution. They come in flexible (for chimneys with offsets) and rigid (for straight flues) configurations. Stainless steel is resistant to corrosion, handles thermal expansion well, and is approved for all fuel types. A properly installed stainless steel liner lasts 20+ years.

Cast-in-Place

Cast-in-place liners are poured as a seamless, insulating liner inside the existing flue. They're more expensive and labor-intensive than stainless steel but are ideal for chimneys with irregular shapes, significant deterioration, or structural concerns. A cast-in-place liner also adds structural reinforcement to the chimney.

Signs Your Liner May Need Replacement

• A Level 2 inspection with video scanning reveals cracks, gaps, or missing sections
• You've had a chimney fire (even a small one you may not have noticed)
• You're installing a new appliance or switching fuel types
• Your home was built before 1950 and has never had the liner inspected
• You notice a strong odor from the fireplace even when not in use
• Your carbon monoxide detector alarms when the fireplace or furnace is running

The Relining Process

For most homes, stainless steel flexible liner installation is the right solution. The process involves: a video inspection to confirm the liner size and configuration needed; lowering the flexible liner from the top of the chimney and connecting it to the appliance at the bottom; installing a top plate and rain cap; and a final inspection with documentation. Most installations are completed in a single day.

Can You Use Your Fireplace While Waiting for Relining?

If your inspection revealed a cracked or deteriorated liner, we strongly recommend not using the fireplace until it's relined. A compromised liner is a carbon monoxide and fire hazard. GEM Chimney & Duct offers same-day scheduling to minimize the wait.