Chimney Sweeps International believes that it shouldn’t just be chimney professionals who understand how your fireplace works. A thorough inspection doesn’t do our customers much good if they don’t understand the results the technician presents them after it is done. For this reason, we have created a playlist of videos explaining what the different parts of masonry and prefabricated fireplaces do, in a way that someone with no prior chimney knowledge will understand. Our goal is to continue to expand our video library, so feel free to contact us with any questions or suggestions for future videos you may have.
What is a masonry chimney?
Masonry chimneys are the most common type of chimney when you think of a standard chimney. They are constructed with non-combustible masonry materials, which include standard brick, mortar, vitrified clay flue liners, and firebrick. Masonry chimneys have detailed design requirements regarding fireplace openings in relation to flue size. Other construction building code requirements must be followed to ensure that the clearances to combustibles will not cause a fire hazard and that the design does not restrict draft and cause the chimney smoke back into the house or cause excessive creosote formation.
What is a prefab chimney?
A prefabricated chimney is a factory-built fireplace typically tested to UL 127 requirements. These metal fireplaces are installed inside a timber framed chimney, and 1 or 2 inch clearance to combustibles is required. These fireplaces typically have a 10-30 year useful life, and after 10 years part and components for these units can be difficult to find. Most manufactures discontinue production of parts because new unit designs and updated code requirements facilitate these changes. The number one cause of prefabricated chimney damage is a rusted or leaking chase cover. These chimneys should be inspected and/or cleaned annually.
What is creosote!
Creosote is formed by unburned wood particles that adhere to your chimney flue passageway when the heated flue gases cool below a temperature of 284 F. As the creosote forms, the buildup can lead to dangerous chimney fires because creosote will ignite at 451 F. The reason why it is advised to burn hard wood is because seasoned hard wood burns at hotter temperatures over 451 F, and creosote buildup ignites during every burning cycle. Pine burns at lower temperatures and can produce many cycles of creosote buildup, and when it gets hot enough, it can cause a dangerous chain reaction chimney fire.
What is a drip edge?
A drip edge is a two-inch overhang at the top of the chimney level with or just below the crown. This is typically constructed from corbelled (stairstep-like) brick that is parged (smoothed with mortar) to make it watertight, but it can also be formed by building the crown from a concrete slab that extends 2 inches over the side of the chimney. A drip edge is designed to “drip” rainwater from the top of the chimney, so this water does not cascade and soak the chimney brick. Brick is porous and will expand and contract during freeze thaw cycles and damage your chimney.
What is a chimney crown?
A chimney crown is concrete at the top of your chimney, and it covers the brickwork that encases the chimney liner, preventing water from pouring into the air space between your flue tiles and the brick exterior of your chimney.
A properly constructed chimney crown is constructed per ASTM 1283 and will have a drip edge, which is a 2-inch overhang level with the crown that helps to drip rainwater away from the sides of the chimney, and an expansion joint that allows the liner to thermally expand and contract during heating cycles.
What are brick joints?
There are three types of brick joints. These are head (vertical), bed (horizontal) and collar (between 2 columns of brick.) Bed and head joints have specific dimensions and strength requirements. The mortar should be weaker than the surrounding brick, so the mortar will fail during tension and compression to make sure that the bricks do not crack. Water that soaks into the brick and mortar joints causes the most damage during freeze/thaw cycles. An industrial strength masonry water repellant is highly recommended.
What is chimney flashing?
Chimney flashing is a crucial component of your chimney for preventing water intrusion. IRC code 903.2.1 states that “Flashings shall be installed at wall and roof intersections, wherever there is a change in roof slope or direction, and around roof openings. Chimney flashing shall be installed to divert the water away from where the eave of a sloped roof intersects a vertical sidewall. Flashing is a metal used to seal off openings in your home from water intrusion. It is constructed with interwoven step flashing into the shingles and counter flashing which laps over the step flashing.
What is a chimney cricket?
A chimney cricket is a roofing component required by IRC code 903.2.2 for all chimneys over 30 inches wide. This is an extension of your roof that runs perpendicular to your main roof between your chimney and the main roof. It covers the width of your chimney and diverts water away from your chimney. This triangular looking ridge separates the water runoff to each side and must be properly constructed based on the slope of the roof and width of the chimney.
What is a smoke chamber?
The smoke chamber is the cavity of your chimney passageway that is directly over the firebox that funnels the smoke from the fireplace to the chimney liner. An improperly constructed smoke chamber will lead to excessive creosote buildup and may cause drafting issues. Smoke chambers are required to be parged (troweled) smooth with refractory mortar and the transition from the top of the damper to the chimney liner should be at less than 30 degrees from vertical and not higher than the width of the firebox.
What are chimney shoulders?
Chimney shoulders are usually corbeled masonry that is the outside transition of the smoke chamber and should be properly capped or sealed to prevent water intrusion. Many times, mortar joints and holes in underlying bricks that construct the shoulders can leak, and this will damage the smoke chamber. Repairing chimney shoulders to be watertight is very important for the maintenance of your fireplace system.
What are lintel joints
Lintel joints, along with firebox profile seams, are the location where the inner and outer hearth meet. The lintel bears on both sides of the fireplace opening and the collar mortar joint that bonds the fireplace front brick surround to the main chimney structure. Lintel and profile seam joints should be filled with refractory mortar if separation cracks are found to prevent transfer of heat to timber wall members.
What is a chimney damper?
A chimney damper is required by building codes and is designed to open and close your chimney flue. While the damper is open, the smoke can travel through the system and expel gases to the outside. If the damper is closed, it can keep the outside air from coming down your chimney. There are several types of dampers, and modern dampers are more energy efficient because they mount on the top of the chimney.
What are profile seams?
Profile seams along a chimney are where the chimney corner meets the home. This intersection many times will be sealed with expandable caulk and is designed to keep sideways rain from penetrating your siding. If this caulk is not periodically resealed, then the old caulk can crack and eventually leak. Water inside your exterior walls can lead to mold formation and moisture damage.
What are firebrick joints?
Firebrick joints are thinner than normal mortar joints and basically glue the firebrick together. Portland cement in regular mortar deteriorates when it cools from high temperatures. This is why firebrick requires special refractory mortar, and joints should be thinner than regular mortar joints.
What is an ash pit door?
An ash pit door is basically a holding pit for ashes of previous fires. The ashes can be swept into the fire pit, and after it fills up from repeated fires, the homeowner can remove the waste from outside the home. This can prevent dusting your home when you clean the ashes from your fireplace.
What is a clean out door?
A clean-out door is required by building code unless the fireplace can be cleaned and serviced from the damper throat. A clean-out door is installed at a location that is 6 inches below the lowest flue tile, as after the liner is swept, the ash debris accumulates at this location. The chimney sweep will open the door and remove the swept debris.
What is a prefab chimney cap?
Prefabricated chimney caps are definitely different than the standard masonry cap. Most of these chimney caps have an air-cooled design, where the cap has spacers to prevent the cap from closing off the top of the liner system. Prefabricated liner systems are designed to circulate air to cool the chimney liner.
What is a storm collar?
A storm collar is designed to shield water away from the chimney chase. Rainwater that coats the exterior chimney liner can drip between the chimney liner and chase cover. If the water penetrates the chase cover, it can rust various components of the top of the fireplace firebox. This can lead to a fire hazard.
What are chase covers
Chase covers are the metal covering at the top of a timber chimney. These manufactured coverings are designed to shed water off the chimney. Most prefabricated chimney manufactures require the chase cover to have cross breaks, which prevents them from rusting. If a chase cover rusts, it can leak into the chimney chase and cause fireplace components to rust.
What is a wood stove insert?
Wood stove inserts are heavy metal boxes that heat and radiate warmth to the home. They are a very efficient way to heat your home; however, due to excessive chimney fires due to draft reduction, wood stoves are required to have a direct connect chimney liner from the wood stove. Newer model wood stoves are also EPA certified and burn cleaner.
Homeowner Training was last modified: February 7th, 2022 by