When is a Chimney Not a Chimney?


Part Two of ‘Why is MY Chimney Leaking?’  

There are quite a number of ambiguous and even confusing terms used in the hearth industry.  Among them is the very basic word ‘chimney’.  If what looks like a chimney and sticks up out of your roof is covered with siding or stucco, it’s probably actually a ‘chase’.  The chase is the framed box and it’s the metal pipe inside that is the chimney.  But all this does is lead to the same questions we answered last month – why is my chimney leaking?  Or my chase or whatever you want to call it?!?!?

In order to safeguard performance and all who live in your home, you must take steps to waterproof your chimney.

In order to safeguard performance and all who live in your home, you must take steps to waterproof your chimney.

Water leaking into your home is a hassle and it can be difficult to locate the source.  Whether you’re venting a fireplace, a stove or even a furnace; the fundamentals of investigating a leak on are the same with a chase as with a chimney:  start at the top and work down to the roofline.  Usually the chase is covered by a sheet metal cover that was fabricated for that specific chase – it looks like an upside down cake pan.  In order to keep it from leaking, the ‘chase cover’ needs to be properly supported and sized for whatever chimneys pass through it.  A properly installed chase cover consists of four components:  the underlying framing and plywood to support it, the cover itself – it should have 4” sides and a drip edge, the chimney collar – the transition from flat to round, and the storm collar – the hat brim-shaped strip of metal that fits around the outer wall of the chimney above the chimney collar.

If water leaks into the chase cover from the top, it typically runs down the outside of the pipe until it reaches something to absorb it.  That can be the ceiling, the top of a freestanding stove or even the walls on the front of a fireplace.  It’s also common for water leaking into the chase to eventually create rust on the top of a built-in fireplace, causing a serious deficiency in the ability of the fireplace to protect the surrounding combustible material.

Because the chase is built very similarly to a standard wall, the sides of a conventional chase are the easiest to evaluate during a leaky chimney diagnosis.  Like anywhere else on your home, water can enter through gaps and/or splits in the siding, cracks in the stucco, and even through holes made by animals.  A comprehensive chimney inspection will include an evaluation of all four sides of the chase.

Where the chase meets the roofline can be the most complicated region of a leaking chimney to diagnose.  Every roof-chimney interface should have an overlapping system that includes both flashing and counter-flashing.  The flashing starts under the roofing materials and runs up alongside the chimney.  The counter-flashing starts out with a ‘cut’ into the side of the chimney and then overlaps the flashing to create a barrier to water intrusion.  Unfortunately, a huge percentage of homes in our community have chimneys that are flashed improperly.  We often see chimneys where the counter-flashing is just placed along the chimney and ‘sealed’ with some type of goop.  WRONG!  Chimneys like these need significant repairs to keep the water out of your home.

To correctly diagnose and fix a leaking chimney/chase, we evaluate the entire chimney/chase as a system: top (cap and cover), middle (siding and/or stucco) and bottom (flashing and counter-flashing).  If any of the three sections is leaking, then the chimney has a potential for water to enter the home.  Our standardized 20-point inspection process is designed to locate the source of leaks and allow us to create a repair program for stopping the water penetration into your home.

To schedule a fireplace/chimney sweeping and/or inspection – call us today at Mountain Man Fireplace and Chimney, Inc – (303) 679.1601 / 838.3882 or electronically at office@MtnManChimney.com.  Semper Fi!