Chimney Liner Installation

Chimney Liner Installation

This page is about putting a liner into a chimney that does not have one, an older unlined masonry chimney, or a chimney being brought into service for a new appliance. If your chimney already has a liner and it has failed, that is liner replacement. If you want the wider picture of when relining is warranted at all, start with chimney relining.

Free estimates, no obligation. Call (888) 882-2070.

Why an Unlined Chimney Is a Problem

In an unlined masonry chimney, the flue gases are in direct contact with the brick and mortar. Three consequences follow, and they are the reason codes require a liner for fuel-burning appliances:

• Gases pass through the mortar joints. Mortar is porous and joints open over time. Combustion products, including carbon monoxide, can migrate through them into wall cavities and living space.
• Heat reaches framing. Masonry conducts heat, and an unlined flue transfers more of it into the surrounding structure than a lined one.
• The masonry deteriorates faster. Flue gases are acidic and attack mortar from the inside, which is how an unlined chimney gradually turns into a leaking one.

None of this is dramatic on any given day, which is why an unlined chimney can go unremarked for a very long time. The risk is cumulative and invisible.

Sizing Comes From the Appliance

The most common technical error in liner work is sizing to the space available rather than to the appliance. Both directions are wrong.

Oversized and exhaust cools before it reaches the top, giving weak draft and, with gas or oil, condensation inside the liner. That condensate is acidic and corrodes the liner from within, so an oversized liner shortens its own life.

Undersized and the appliance cannot vent properly, which is a safety problem rather than a performance one.

A wood stove insert typically vents through six inches, some units eight. Any quote should state the diameter and relate it to your appliance's outlet.

What Gets Installed

316Ti stainless is a titanium-stabilised grade that resists the acidic condensate gas and oil produce, and it is the right specification for those fuels. 304 suits wood-burning. Aluminium is limited to certain gas appliances and is not suitable for wood or oil. Cast-in-place pours a cementitious liner that also adds structural strength, which is worth considering where the masonry itself is weak.

Flexible corrugated liner negotiates offsets, which most masonry chimneys have. Rigid has a smoother bore but only suits a genuinely straight flue, it cannot pass an offset a flexible liner will.

Insulation keeps exhaust hotter on the way up, improving draft and reducing the condensation that corrodes liners from within. Where a liner sits inside a much larger flue, it is closer to necessary than optional.

The Florida Case

Two things shape this locally. First, gas condensate rather than creosote is what attacks liners here, because so many Florida fireplaces are gas or converted, which is why 316Ti matters on a gas installation and why insulation on an oversized flue is not an upsell.

Second, water from above. A cracked crown, a missing cap or a rusted chase cover lets rain into the flue. Installing a new liner beneath one of those means the new liner starts with water running down it, so the crown or cap belongs in the same job.

Freeze-thaw, which most national liner content leans on to explain flue damage, is not a factor here.

What Drives the Cost

The spread comes from what the flue will accept, what is going on it, and whether anything has to come out first. At the modest end, a short straight flue with good roof access, lined in stainless and connected at the appliance inside a day. At the far end, a stack whose flue wanders, whose survey turns up an old liner to remove, and whose tired masonry wants a poured cementitious liner instead.

What the chimney decides

• The run and the bends in it. Liner is priced by the foot, so a two-story stack takes more of it, and offsets slow the feed and rule out rigid liner.
• What the survey finds inside. The camera settles whether the flue is genuinely unlined, and where an old liner turns up it comes out before the new one goes in.
• What is being connected. Diameter follows the appliance outlet, not the space available, and the fuel fixes the grade: 316Ti for gas and oil, 304 for wood, aluminium for certain gas units only. A liner inside a much larger flue also wants insulating.
• The top, and getting to it. A cracked crown or missing cap lets rain into a flue about to be lined, masonry sometimes needs making sound before a top plate goes on, and poor access stretches it.

What you decide

• The appliance, first. Diameter comes from its outlet and grade from its fuel, so settle the unit before the flue is sized.
• Metal or a poured liner. Where the masonry is deteriorating, a cast-in-place pour forms the flue and adds strength at once. It is the largest of the options and unnecessary on a sound chimney.
• Crown or cap in the scope. If either is failing, yes: a new liner under a cracked crown starts with water running down it, and one visit saves paying twice for access.
• Not much else, honestly. Grade follows the fuel and insulation follows the flue, so leaving it off a flue that wants it quotes a shorter-lived installation.

The number comes from the survey. The crew camera-surveys the flue, measures its height and its width against the appliance outlet, then puts grade, diameter, insulation and exclusions in writing, free and itemised. Nobody can tell from the room below how far the flue rises or what is already inside it, so a phone figure would be a guess.

What to Ask

• Did you camera-survey the flue to confirm it is unlined?
• What diameter, and how does it relate to my appliance outlet?
• What grade, and why that one for my fuel?
• Is insulation included, and if not why not on this flue?
• Is the crown or cap being dealt with in the same job?

Free estimates, no obligation, call (888) 882-2070.