THE HIDDEN DANGER OF UNLINED CHIMNEYS IN OHIO HOMES

Why Unlined Chimneys Are Dangerous

A chimney liner serves as a containment barrier. It keeps heat, sparks, creosote, carbon monoxide, and other combustion byproducts inside the flue and away from your home's structure. Without a liner, three serious risks exist:

Fire hazard. Heat transfers directly through bare masonry to adjacent wood framing. Over time, this repeated heat exposure can cause pyrolysis — a process where wood gradually chars at lower and lower temperatures until it can ignite. A chimney fire in an unlined flue has no barrier preventing it from spreading to the house structure.

Carbon monoxide exposure. Mortar joints in old chimneys deteriorate over decades. Gaps and cracks in the mortar allow carbon monoxide and other flue gases to leak through the chimney walls and into living spaces. CO is odorless and colorless — you cannot detect it without a functioning alarm. Even small, chronic leaks are dangerous.

Accelerated chimney deterioration. Without a liner, acidic combustion gases attack the mortar joints from the inside. This erosion happens faster than exterior weathering and weakens the chimney structure from within, eventually compromising its structural integrity.

How to Tell If Your Chimney Is Unlined

You cannot determine whether your chimney has a liner by looking at it from the outside. The liner is inside the flue. Here are the ways to check:

• Look up from the firebox: Open the damper and look up into the flue with a flashlight. If you see bare brick and mortar joints instead of smooth clay tiles or a metal tube, the chimney is likely unlined.
• Check the home's age: Homes built before 1940 in Ohio were commonly built without chimney liners. Some homes from the 1940s-1960s may also lack liners depending on the builder and local codes at the time.
• Get a camera inspection: A chimney inspection with a video camera provides a definitive answer. The camera travels the full length of the flue and shows exactly what is — or is not — lining the chimney.

If you are buying an older home, this is one of the most important things a Level II inspection can reveal. A missing liner is not something you can see during a walkthrough, and it is not something a general home inspector will catch.

Ohio Code Requires Chimney Liners

Ohio building code, following NFPA 211 standards, requires that chimneys have a listed liner appropriate for the type of fuel being burned. An unlined chimney does not meet code, regardless of when it was built. While existing homes are not typically forced to retroactively comply, using an unlined chimney for a fireplace, wood stove, or furnace is operating outside of code — and outside of safe practice.

Insurance implications also exist. If a chimney fire or CO incident occurs and an inspection reveals the chimney was unlined, your homeowner's insurance claim may be complicated by the code non-compliance. Relining is both a safety upgrade and a liability protection.

The Solution: Stainless Steel Relining

The standard solution for an unlined chimney is installing a stainless steel liner. The process involves lowering a flexible stainless steel tube down the full length of the flue, connecting it to the appliance or fireplace at the bottom, and capping it at the top with a rain cap and storm collar. The space between the liner and the chimney walls is typically insulated to improve draft and protect against heat transfer.

Stainless steel relining can be completed in most homes in a single day without any demolition or exterior modification to the chimney. The liner is sized for the specific appliance — wood-burning fireplaces, gas furnaces, and oil furnaces each require different liner sizes and grades of stainless steel.

Quality stainless steel liners come with lifetime transferable warranties, meaning the investment carries over if you sell the home. For a home with an unlined chimney, relining is one of the highest-value safety improvements you can make.

Older Homes in the Twinsburg Area

While most of Twinsburg's residential growth happened in the 1980s-1990s, older homes exist throughout Twinsburg Township and surrounding areas like Northfield, Macedonia, and parts of Hudson. These pre-war and early post-war homes are the ones most likely to have unlined chimneys. If you own or are buying a home built before 1960 in the area, a camera inspection of the flue is a critical safety step — not optional maintenance, but a genuine safety evaluation that determines whether your chimney is safe to use at all.