The variables behind a relining quote

The appliance picks the liner before the chimney does

The cost to reline a chimney starts with whatever burns at the bottom of it, since a liner is sized to the appliance, not to the chimney it runs through. FBC Residential R1003.11 requires the lining to match the kind of appliance connected to it, per that appliance's listing and its maker's instructions. For an appliance, R1003.14 adds that the flue cannot be smaller in area than the appliance's connector.

Each of these calls for a different liner: an open wood-burning fireplace, a wood insert, a gas appliance. Chapter 10 of the code also ties the flue area of a masonry fireplace to the size of its opening. A liner that suits one appliance can be wrong for another, so the first question on a relining call is what the flue serves today and what it will serve after the work.

Stainless, aluminum or poured in place

Three liner families come up on relining jobs, each with a different scope. Stainless steel liners, rigid or flexible, are listed to UL 1777, the standard for chimney liners, and come in alloys matched to the fuels named in their listing. They cover wood appliances, and gas appliances where the listing allows.

Aluminum liners are listed for certain gas appliances only. They are lighter and quicker to install, and that is where their use stops: they are not a wood-burning liner. Cast-in-place liners are a cement-based mix poured around a form inside the old flue, using a listed system. They can add strength to a tired chimney but take more material, more time and a cure period.

Height, shape and bends in the flue

Length is the plain variable: a taller chimney takes more liner and more time to feed it. Shape is the less obvious one. A round liner can drop into a rectangular clay flue with room to spare, or it can bind at a joint, and a large flue can call for an oval liner to keep enough area without breaking out tile.

Offsets decide between rigid and flexible. A flue with a bend partway up takes a flexible liner, or rigid sections joined with listed elbows. Each bend adds pulling time, and a sharp one can mean opening the chimney wall at the bend to guide the liner through.

Insulation, when the listing calls for it

Some liner listings require an insulation wrap or a poured insulating mix around the liner. The installation instructions say when, for example where the chimney lacks the airspace to framing that the listing depends on. A wrapped liner also holds more heat in the rising gases, and warmer gases draw better.

Insulation adds material, and on a snug flue it raises a fit question. A wrapped liner is bigger than a bare one, and that is the point where tile removal can enter the estimate.

Breaking out old tile to make room

Clay tile that has cracked, shifted or collapsed can block a new liner. A flue that is just big enough for a bare liner may be too small once insulation is added. In either case the old tile comes out first, worked downward with a breaking tool while the debris is caught at the smoke chamber.

Tile removal is slow, dusty work. It gets a separate entry, which shows its share of the job and keeps the choice between an insulated liner and a bare one visible on paper.

A chimney fire can also be the reason relining comes up, since a fire hot enough to crack tile can leave a flue that nobody can call sound. The inspection after the fire decides whether relining is needed.

The parts at each end of the liner

At the top, a top plate seals the liner to the crown or the old tile, and a cap with spark arrestor mesh sheds rain and bars animals. At the bottom, it connects to the appliance, or on an open fireplace to a smoke chamber that may need parging so the smoke has a smooth path into the new liner.

Relining is also a good time to check the crown. A new top plate sealed to a cracked crown will leak around its edges, so crown work can appear on the same estimate, itemized apart from the liner.

Access to the roof and the firebox

Liners go in from the top. Roof height, pitch and covering decide how the crew stages a long coil of flexible liner or a stack of rigid sections. A tall stack on a steep tile roof takes more setup than a short one on a low shingle roof.

Inside, the firebox or the appliance opening decides how easily the bottom connection is made. An insert that has to come out and go back in adds its own time, and so does a narrow firebox with a damper frame in the way.

Six relining jobs compared

With height and access set aside, relining jobs line up like this:

• An aluminum liner for a gas appliance whose listing allows it, in a straight flue.
• A flexible stainless liner in a straight flue with sound tile and no insulation required.
• The same liner with an insulation wrap, where the instructions call for one.
• A flue with offsets, where the liner is pulled through bends or joined with elbows.
• A flue where old tile is broken out before the new liner goes in.
• A cast-in-place liner, formed and poured inside the old flue.

What a new liner does not fix

A liner makes the flue sound again. It does not repair the crown, the flashing, loose brick above the roof or a firebox with open joints, and none of those should be hidden inside a relining price. If the chimney needs them, they are itemized, and the order they happen in, before or after the liner, is spelled out.

The cap works the same way. The relining job includes a cap for the new liner, but the rest of the stack is judged by its condition.

Why two liners of the same type can price differently

Height and access alone can move a job up or down the list above. A short straight flue on an easy roof and a tall offset flue on a steep one can both take a flexible stainless liner and still be very different jobs.

Whether a quote calls it chimney relining cost or chimney liner installation cost, the written estimate should name each variable: the appliance, the liner type and size, insulation, tile removal, the top plate and the cap, plus any work on the crown or the smoke chamber. Reading those lines tells you which of them moved your number.