Masonry Fireplace Relining: Why It’s One of the Most Complex Chimney Repairs

Relining an open-burning masonry fireplace is one of the most challenging repairs that can be performed on a chimney system. Unlike wood stove or fireplace insert liners, open fireplaces require very large-diameter stainless steel liners—often around 16 inches in diameter—to maintain proper draft and safe operation.

By comparison, a gas or wood insert is usually a 1–2 day job. The insert’s liner simply runs down inside the existing chimney, and the chimney itself is not opened up. Keeping an open-burning fireplace means connecting a new liner to the top of the smoke chamber, which is far more involved.

Because of the size of these liners and the way masonry chimneys are constructed, relining is rarely as simple as lowering a liner down the chimney.

Step 1: Evaluating the Existing Flue

Most masonry chimneys contain terracotta clay flue tiles. Before a stainless steel liner can be installed, we must determine whether the existing clay liner can be removed to make room for the new liner.

In properly constructed chimneys, the clay liner is separated from the surrounding masonry by an expansion space. This often allows specialized rotary equipment to break apart and remove the clay liner.

However, some chimneys were built with mortar, concrete, or masonry packed tightly around the clay flue tiles, with no air space. When this occurs, the rotary tool cracks the tile but it doesn’t come off, because it is bonded to the masonry around it. Removing the clay liner may then be extremely difficult or impossible without damaging the chimney structure.

Step 2: Creating Access to the Smoke Chamber

The bottom of the new liner must be connected to the fireplace throat and smoke chamber area, so we need access to the top of the fireplace. How we get there depends on how the fireplace is built.

Brick or masonry firebox: We open the slanted back wall of the fireplace throat from inside the fireplace, climb in, and use specialized tools and adapters to connect the bottom of the stainless liner to the top of the smoke chamber. We then rebuild the back wall with new firebrick.

Metal firebox: A metal firebox cannot be cut open and welded back together. Doing so destroys its integrity, and even a skilled welder’s welds would eventually fail. Instead, we reach the smoke chamber from the outside by cutting an access opening through the chimney masonry—typically about 2 feet wide by 3 feet tall—make the liner connection, and patch the opening with masonry materials.

For exterior access, the chimney’s construction and location matter:

• Bare cinder block is the most straightforward to open and repair.
• Brick is harder, but still very doable.
• Stone veneer over block or brick adds another layer of difficulty. We have to get through the stone and then find out what is underneath—brick or block, whether the block is filled with concrete or mortar, and whether there is rebar.
• A chimney that runs mostly outside the house is easier to reach. If the lower part of the chimney is inside the home—behind a wall in a bedroom, bathroom or garage—that wall has to be opened and repaired, which means more mess, more disruption and more cost.

After the liner is installed, all affected masonry must be rebuilt and restored.

Step 3: Installing the New Stainless Steel Liner

The stainless steel liner is lowered through the chimney and connected to the smoke chamber. Due to the large size and weight of these liners, installation often requires roof work, specialized equipment, and multiple technicians.

Every liner we install is insulated to meet the UL 1777 standard. The insulation takes up about an inch all the way around the liner, and the liner also needs some clearance so it doesn’t get stuck as it is fed down the chimney. Both reduce the size of liner that will fit—and therefore the area available for smoke and gases to flow through.

Unlike smaller wood-stove liners, open-fireplace liners are heavy, expensive, and more difficult to maneuver within an existing chimney structure.