If you've ever searched for a top mount or side mount chimney cap — also called a chimney topper, chimney rain cap, chimney cover, chimney shroud, or chimney surround — you've probably seen the stainless steel options from the big box stores. They get the job done. But most homeowners don't know a custom fabricated chimney cap is even an option — one built to your exact dimensions, in copper, stainless steel, or aluminum, that actually looks like it belongs on the house.
Here at Archaic Metal, that's all we make. Every cap is cut, formed, and finished by hand. So let's walk through the difference between top mount and side mount, and how to know which one your chimney needs.
Top Mount
What it is: A top-mount cap sits directly on top of the chimney crown and is secured with construction adhesive. The cap rests flat on the masonry surface with no vertical skirt — the screen opening sits centered over the flue, extending 3" beyond the screen on all four sides.
This style is ideal when:
- Your chimney is irregular, out of square, or built from stone
- You want a cleaner, lower profile look without a vertical skirt showing on the sides
- You prefer a smaller cap footprint, which also keeps the cost down
- Your masonry chimney has a beautiful slab of stone on top — it keeps the cap sitting above the stone rather than hiding that nice, finished edge
That last point is one we feel strongly about. If a craftsman laid a nice stone cap on your chimney, a top-mount installation keeps it visible. A side-mount skirt would hide that nice, finished edge.
How to measure for a top-mount cap: Measure the area where you want the screen to sit on the chimney top, then add 6" to both the length and width. That's your cap size.
Side Mount
What it is: A side-mount cap wraps around the outside of the chimney with a vertical skirt that covers the upper portion of the chimney wall — typically 3 to 4 inches down the side, secured with screws through the skirt into the masonry. The skirt covers the entire chimney crown.
This is the preferred installation method in most situations. The skirt provides full coverage of the chimney crown, creates a tighter seal against wind-driven rain, and gives the cap a more substantial, finished appearance sitting on the chimney.
If your chimney has clean, square edges and you want the most weathertight fit, side mount is usually the right call.
How to measure for a side-mount cap: Measure the full outside length and width of the chimney crown. That's your cap size.
Still Not Sure?
Measure your flue opening and the outside of your chimney crown. If the top surface is flat and square, either style works. If it's stone, irregular, or you want to show off the masonry, go top mount. If you want maximum weather protection and a tighter fit, go side mount.
Not sure how to measure? Check our measuring guide → or call or text Sean at (609) 352-9840. Every cap we make at Archaic Metal is custom — if you have an unusual chimney or an in-between size, reach out. We build to fit.
Browse our custom chimney caps → — custom fabricated to cover your entire chimney top. Ships anywhere in the USA.
Sean has 32 years of experience fabricating and installing sheet metal components, copper roofing, and custom architectural metalwork — including historic preservation projects on schools, churches, and government buildings. Every cap that ships from Archaic Metal is built by hand in New Jersey.