Unlined Stack

Definition

An unlined stack is a chimney or vent constructed of a single pipe without any internal lining.

Purpose

Unlined stacks are used to vent combustion gases from fireplaces, stoves, or furnaces. While they serve the basic function of removing smoke and gases, they lack the durability and safety features of lined stacks, making them more susceptible to heat damage and corrosion.

Examples of Use

• Old Fireplaces: Older homes with unlined chimneys that vent fireplace smoke directly through a single pipe.
• Wood Stoves: Basic wood stove installations using unlined vents to exhaust smoke.
• Industrial Applications: Certain industrial processes that use unlined stacks for venting non-corrosive gases.

Related Terms

• Lined Chimney: A chimney with an internal lining made of clay, ceramic, or metal to protect against heat and corrosion.
• Flue: A duct or pipe for conveying exhaust gases from a fireplace, furnace, or boiler to the outside air.
• Vent Pipe: A pipe that allows the escape of gases or smoke from a building.

Notes

Unlined stacks are generally less safe and less efficient than lined stacks. Modern building codes often require chimneys and vents to be lined to improve safety and performance.