Chimney Flue Repair and Relining in New Jersey

The flue is the passage that smoke and gases travel through, and the liner is the material forming its walls. In most masonry chimneys that liner is a stack of clay tiles set inside the brick. Newer relining work usually means a stainless steel pipe dropped down the old flue. A chimney is the whole structure around it, which may hold one flue or several.

The liner has two jobs. It keeps heat from reaching the wood framing that sits near a chimney, and it keeps corrosive gases and moisture off the brick and mortar. New Jersey's residential code says masonry chimneys shall be lined, with the lining appropriate for the appliance connected, and the options it lists include clay flue lining and listed chimney lining systems complying with UL 1777. Many houses built long before that rule have thin or partial liners, and some of the oldest stacks have sections with none at all.

Pieces of clay tile in the firebox, at the base of a furnace flue or in the cleanout are the plainest sign a liner is breaking up. Other signs include tile flakes on the smoke shelf, a flue that smells strongly in damp weather, stains or dampness on an inside wall beside the chimney, and a water heater or furnace that spills exhaust at the draft hood. A sweep with a strong light can show cracked tile, missing mortar between tiles, and offset joints.

Damage is easy to miss on a stack nobody watches, and on a flue that only vents a basement appliance. Cooler, wetter gas exhaust wears at old tile and mortar from the inside. A chimney fire can crack tile in one night, and creosote glaze can hide the damage until the flue is cleaned. Treat tile in the firebox as a stop sign: leave the fireplace unlit and have the flue looked at before the next fire.

A flue with limited, reachable damage can often be repaired, while one with damage along its length, or with no sound liner at all, is usually better relined. A loose tile at the top, a joint near the crown or a section at the base of the flue can be handled on its own. Cracks scattered through the height of a stack are out of reach from either end without opening the masonry, so a new liner dropped down the inside is the practical repair.

Relining has other advantages. A new liner gives a continuous, smooth passage sized to the appliance, and it can often go in without opening a wall or disturbing plaster. It also lets a damaged flue stay in service where taking the stack apart would be out of proportion to the problem. The trade-off is the size of the old flue. A liner takes up room, so a large fireplace may lose some draft capacity if the new pipe is too small for the opening. That is checked before anything is ordered.

A new high-efficiency furnace usually vents through plastic pipe in a side wall, which takes it off the chimney and leaves the water heater by itself in a flue built for a far larger load. That oversized flue never warms up properly. The small stream of exhaust cools on the way up, draws weakly and condenses on the tile, and the moisture and acids work at the mortar. The chimney was fine for decades, and the same flue can become a problem the week the furnace changes.

A sound flue has to suit the appliance using it, and past performance does not settle that question. Across the two-family blocks of Elizabeth, Bayonne and Clifton, where a boiler swap often leaves a lone water heater in the old stack, a liner sized to what remains is the common answer. Oil-to-gas conversions raise the same issue. Before new equipment is connected, ask the installer what the flue has to be, and have the chimney checked against that answer.

The right liner follows the appliance, so a fireplace, a stove and a gas water heater may each call for something different. Clay tile suits many wood fireplaces when it is sound, and a stainless steel liner is the usual relining choice for gas and oil equipment. A wood stove or an insert that heats a house through the winter calls for a liner sized to the stove's outlet, as stoves in Howell and Hopewell keep a flue working harder than a weekend fireplace does.

Every estimate starts from what vents into the flue now, and you see photographs of the tile before a repair or a liner is recommended. The evaluation and the estimate are free. Veteran owned and licensed and insured (NJ HIC 13VH13654300), AMG answers 24 hours a day, 7 days a week, so a piece of tile in the firebox can be looked at before the next fire. Ask the town building department whether a permit applies to the relining, and tell your heating contractor what the flue has been fitted with.