Is It a Chimney Chase or a Masonry Stack? What Southwest Philly Homes Have
Not every chimney is solid brick. Knowing whether your home has a true masonry stack or a framed chase changes how it should be inspected and maintained. Here is how to tell.
Two very different things called a chimney
The word chimney covers two genuinely different kinds of construction, and knowing which one your home has matters more than most owners realize. The first, and the kind that dominates the older housing of West and Southwest Philadelphia, is the true masonry stack, a chimney built of brick and mortar from the ground or the firebox all the way up past the roof, with the flue running inside that solid masonry column. This is what most people picture when they think of a chimney, and it is what the Victorian twins of Overbrook and the brick rowhomes of Kingsessing and Paschall almost universally have.
The second kind is a framed chase. Instead of solid masonry, a chase is a wood-framed box, often finished on the outside with siding, brick veneer, or stucco, that encloses a metal or prefabricated flue running up inside it. Chases are common on newer construction and on additions, including some of the mid-century and newer homes scattered through Southwest Philadelphia neighborhoods like Eastwick. From the street a brick-veneer chase can look much like a masonry stack, but inside it is a completely different animal, and it fails in completely different ways.
How to tell which one you have
There are a few practical ways to tell a masonry stack from a chase without climbing on the roof. A true masonry chimney is solid brick all the way up, so the stack is heavy, the brick is full-depth, and at the top you will see a masonry crown with one or more clay or metal flue liners poking through it. A chase, by contrast, is a lighter framed structure, and at the top it is typically finished with a chase cover, a flat metal cap over the whole box, with a metal flue pipe and often a rain cap rising out of it, rather than a masonry crown. If the top of your chimney is a metal cover rather than a mortar crown, you are very likely looking at a chase.
Inside the house, the clues continue. A masonry chimney usually has a substantial brick or masonry presence, a real firebox of firebrick, and the heft you would expect of a brick column. A chase often houses a prefabricated metal firebox, a factory-built unit rather than masonry, and the surrounding structure feels like framed wall rather than solid brick. The home's age and history help too. A century-old rowhome or twin almost certainly has a masonry stack, while a newer home, an addition, or a home where a fireplace was added later may well have a framed chase. When in doubt, an inspection settles it quickly.
- Masonry stack: full-depth brick, mortar crown, clay or metal liners through the top
- Framed chase: lighter framed box, metal chase cover at the top, prefab flue pipe
- Masonry firebox of firebrick versus a factory-built metal firebox
- Older twins and rowhomes are almost always masonry
- Newer homes, additions, and added fireplaces are more often chases
Why the difference changes the maintenance
The two kinds of chimney need different attention because they fail differently. A masonry stack's enemies are water and freeze-and-thaw, washing out the mortar, spalling the brick, and cracking the crown, so its maintenance centers on repointing, crown repair, a good cap, and keeping the flue swept and the liner sound. A chase, on the other hand, has no mortar to wash out, but it has a chase cover that can rust and leak, framing that can rot if water gets in, and a prefabricated flue and firebox with their own service life and their own parts. A leaking chase cover that rots the framing inside the box is a classic chase failure that has no equivalent on a masonry stack.
Because of this, an inspection has to know which kind it is looking at and check the right things. On a masonry stack we are scoping the flue and examining the crown, the brick, and the joints. On a chase we are looking at the chase cover, the flashing, the condition of the framing and the exterior finish, and the prefabricated components inside. Treating one like the other misses what actually matters. This is part of why a real inspection is worth more than a glance, the inspector who knows the difference checks the failure points that your specific kind of chimney actually has.
Knowing what you own
For a Southwest Philadelphia homeowner, the takeaway is to know which kind of chimney you have, because it shapes everything from what can go wrong to what maintenance makes sense. If you have a true masonry stack, which most older homes here do, your attention goes to the brick, the crown, the cap, and the flue. If you have a framed chase, more likely on a newer home, an addition, or an added fireplace, your attention goes to the chase cover, the flashing, the framing, and the prefabricated parts. Either way, knowing what you own lets you maintain it intelligently rather than guessing.
If you are not sure which you have, an inspection will tell you in short order, and a good one will then check the things that actually matter for your kind of chimney. There is no shame in not knowing, plenty of owners assume a brick-veneer chase is solid masonry, or are surprised to learn their old chimney is exactly the heavy brick stack it appears to be. The point is simply to find out, so that the care your chimney gets matches the way it was actually built.
Not sure whether you have a masonry stack or a framed chase? An inspection tells you fast and checks the failure points your kind of chimney actually has. Call Philly Flue Pros at 215-602-7630.
Call 215-602-7630 and we will read the chimney honestly and quote it in writing.