Stove Pipe Types: Single-Wall, Double-Wall and Class A Chimney

Chimney Academy · Compare options · Updated October 2026

Two jobs: the connector and the chimney

Think of the system in two pieces. The connector runs from the stove’s flue collar to the chimney. The chimney carries exhaust the rest of the way up and out above the roof. They sit at very different temperatures and are built differently for that reason.

Connector pipe lives in the room, where it gets hot and radiates heat to nearby walls and furniture. Chimney pipe passes through ceilings, attics and roofs and is insulated and tested to resist heat soaking into framing. When people say “stove pipe” they usually mean the connector, but some use the phrase for all of it, which is where conversations go wrong.

Our guide to thimbles and connector pipes goes deeper on the joint where the connector meets the chimney.

The three types side by side

“Class A” is a common trade name for factory-built chimney systems tested to a high-temperature standard (UL 103 HT). Manufacturers also call these all-fuel systems because they can serve wood, oil, gas and coal appliances, subject to each product’s own limits. The wording matters because a gas vent labeled B-vent is a different, lower-temperature product and does not belong on a wood stove.

Where each type is typically used

Specific rules come from the stove’s listing and the local code, so the points below are general patterns, drawn from manufacturer instructions.

Single-wall connector

One stove manufacturer’s manual allows black steel or stainless single-wall pipe of a minimum thickness for its stove and bars aluminum and galvanized steel. It also limits how long and how steep the run can be, and caps the number of sharp elbows. Another connector maker states plainly that its all-fuel chimney instructions prohibit installing single-wall pipe through the wall thimble. The point is that single-wall pipe stays in the room and meets the chimney at a thimble or support box designed for it.

Double-wall connector

A manufacturer of close-clearance double-wall pipe describes it as acceptable anywhere single-wall is allowed, and as a way to use smaller clearances where the stove manual permits them. The same instructions say not to enclose it or run it through walls, ceilings, attics or closets, and not to connect more than one wood-burning appliance to a single connector and chimney. Its stated clearances are specific to that product (6 inches to walls and 8 inches to ceilings), so do not apply those figures to other pipe or to your stove.

Class A chimney

Class A systems pass through framing using matching support boxes, firestops and roof flashing, and they depend on a minimum air space from combustibles that must never be filled with insulation. They are the usual choice when a stove vents through the ceiling and roof, or up the outside of a house in a chase.

Why mixing parts is a problem

A chimney system is listed as a complete assembly. The test lab checks the pieces together at high temperatures with specific clearances. One all-fuel chimney manual puts it bluntly: use only parts from that system, do not match parts from another maker, and avoid improvised solutions. It also warns that departing from the instructions can void the warranty and may affect your homeowner’s insurance and the product’s listing.

Real-world mixing looks like this:

• Single-wall pipe pushed through a ceiling support box built for double-wall or Class A.
• Connector pipe pressed into a chimney with a crimped adapter that was never designed for that size.
• A different brand’s section added because it “looks the same.”
• Gas B-vent used for a wood stove, or galvanized duct used in place of stove pipe.

Each of these can hold up for a season and still leave a gap in heat protection or a leak at a joint that you cannot see. That is why a mismatch is worth correcting even if nothing has gone wrong yet.

How to find out what you have without touching anything risky

You can learn a lot from the floor.

• Labels. Listed connector and chimney sections carry stamped or printed labels with a maker’s name and a model or listing mark. Look at pipe sections you can see without climbing or taking anything apart.
• The stove’s data plate and manual. The manual names the pipe type, minimum diameter and clearances. If it is missing, most manufacturers post manuals online by model number.
• Where it goes. Is there a masonry chimney, or does the pipe go into a metal chimney through the ceiling? Our guide on masonry versus factory-built chimneys explains how to tell.
• Old photos and permits. Closing documents or earlier contractor paperwork may name the system.

Do not remove sections to look inside, and do not climb on the roof to check the cap. Those are inspection tasks.

When to call a professional

Arrange an inspection when you bought a house with a stove already in it, when pipe runs through a wall or ceiling and you cannot tell why, when rust, sagging or loose joints show up, or when you plan to replace the stove. A chimney inspection checks the connector, the chimney and how they join. If pieces need to change, a chimney repair visit can address them, and AM explains its findings and options before any work begins.

Bring the questions below to the appointment.

1. Is the connector the type the stove manual calls for?
2. Is the chimney listed for this fuel, and is it one system or a mix of brands?
3. Are clearances to walls, ceilings and the hearth being met?
4. Are there any joints, thimbles or supports that need replacing?

What this guide does not cover: it gives no clearance numbers for your home and cannot tell you whether your installation is correct. Those answers come from your appliance manual, the product listings and your local code official. Our guide to clearances to combustibles explains why those numbers are so strict.

Frequently asked questions

Related reading

• Thimbles and connector pipes
• How a wood stove should be vented
• Masonry vs factory-built chimney: how to tell
• Clearances to combustibles
• Chimney inspection