Chimney Liner for an Open Wood Fireplace: What Works

Why open fireplaces get relined

Most open fireplaces in older homes across the region vent through clay tile flues, or through no liner at all in the oldest brownstones and rowhouses. Over the decades, tiles crack from heat and settling, joints open, and freeze-thaw damage at the top lets pieces fall. A chimney fire can crack a whole run of tile in one evening. When an inspection finds a damaged or missing liner, the fireplace should not be used until the flue is restored.

Relining gives the smoke a sealed, continuous path again and protects the house framing around the chimney from heat and exhaust.

Sizing is the whole game

A stove or insert is a closed box with a small outlet, and its liner matches that outlet. An open fireplace is different: the flue has to pull smoke through the entire front opening, along with all the room air the fire draws in. A flue that is too small for the opening cannot keep up, and smoke spills out the top of the fireplace into the room.

Trade guidance commonly sizes a fireplace flue as a fraction of the opening's area, with the exact ratio depending on the flue shape and the chimney height. The fireplace's width, height and depth are measured, the chimney's height is noted, and the liner is chosen from sizing tables to match. This is why a liner that works perfectly for an insert would make the same fireplace smoke if it were burned open.

The liner options compared

Each option has a place. The chimney's shape, the fireplace size and the condition of the masonry usually narrow it to one or two.

Stainless steel for fireplaces

Stainless steel liners are the most common choice for relining a fireplace. Round liners move air most efficiently, but a large round liner may not fit inside a rectangular clay flue without the tile being removed. Oval and rectangular liners exist for exactly that reason: they use more of the available space so the liner can be large enough for the opening.

For wood fireplaces, the liner is usually insulated, either with a wrap or a poured insulating mix around it. Insulation keeps the smoke warmer so it drafts better and condenses less creosote, and in older chimneys it often helps meet the liner's required clearance to nearby framing.

Cast-in-place and clay tile

A cast-in-place lining is formed inside the existing flue by inflating a form, pouring a lightweight mortar around it and removing the form once it sets. It fills gaps and bonds to the old masonry, which suits chimneys with offsets, irregular flues or weak mortar. It reduces the flue's size somewhat, so the original flue has to be large enough to start with.

Clay tile is the original material for most fireplace flues. Replacing it inside a standing chimney is difficult below the top few feet, so it is usually practical only where damage is near the top or the chimney above the roof is being rebuilt anyway.

What happens at the damper and smoke chamber

The liner has to connect to the smoke chamber, the sloped space above the damper that funnels smoke into the flue. With a stainless liner, the old throat damper usually comes out so the liner can be connected, and a top-sealing damper mounted on the chimney top replaces it. A top damper seals better than most old cast iron dampers, which helps keep heated room air from escaping when the fireplace is not in use.

The smoke chamber itself is often rough, stepped brick in older fireplaces. Smoothing and sealing it with a refractory parging helps smoke move into the liner cleanly and removes ledges where creosote collects.

When a liner is not the right answer

Some fireplaces are too small or too shallow for comfortable open burning, especially the coal-era fireplaces in many brownstones. Others sit in chimneys too narrow to take a liner big enough for the opening. In those cases, the options shift: reduce the opening, install an insert or stove with a smaller liner, convert to gas with venting the gas unit's manual allows, or use the fireplace decoratively with the flue capped. An honest inspection should lay those out rather than force a liner that will smoke.

Signs your fireplace flue needs attention

Owners usually learn about a failed fireplace liner from an inspection, but some signs show up first. Terra cotta shards on the smoke shelf or in the ash are fragments of flue tile. Smoke smell in an upstairs room or closet next to the chimney while a fire burns can mean smoke is escaping through open joints. Dark staining on a chimney breast wall, or heat you can feel on a wall that used to stay cool, are reasons to stop and call.

An inspection after a chimney fire is especially important, since heat can crack a whole run of tile without any visible sign from the room.

• Tile shards on the smoke shelf or in the ash
• Smoke smell in rooms or closets next to the chimney
• Stains or warmth on walls along the chimney breast
• A fireplace that started smoking after years of drawing well

What to expect from the job

The visit begins with an inspection and measurements of the fireplace opening and flue. The flue is swept, damaged tile and obstructions are cleared, the liner is installed and connected to the smoke chamber, and the top is finished with a plate, cap and top damper as needed. Before the crew leaves, a test fire or draft check confirms the fireplace draws. You get the scope, the options and the price on paper, free, before any work starts. Many fireplace relines take a day or two, depending on the liner type and any work at the top.