How Do You Install a Through-the-Wall Chimney in a Garage?

Can You Put a Wood Stove in a Garage?

Yes, if nothing in the stove's manual or listing rules out a garage, your building department approves it and the stove meets your code's garage clauses: in the IRC, its ignition source at least 18 inches above the floor, and protection from vehicles.

Before you buy a wood stove for your garage, settle three things in this order:

1. What the stove's manual and listing label say about a garage, about clearances and about floor protection.
2. What your building department asks for: a permit, the code edition and local amendments, an inspection.
3. Which chimney route fits the garage: through the wall or through the roof.

What the Code Says About Appliances in a Garage

Where your state or town has adopted the International Residential Code (IRC), Chapter 13, three of its clauses reach a stove in a garage. One is written for garages, one for any place where a vehicle could damage an appliance, and one for every appliance:

• Section M1307.3, Elevation of Ignition Source: “Appliances having an ignition source shall be elevated such that the source of ignition is not less than 18 inches (457 mm) above the floor in garages. For the purpose of this section, rooms or spaces that are not part of the living space of a dwelling unit and that communicate with a private garage through openings shall be considered to be part of the garage.” Its exception: “Elevation of the ignition source is not required for appliances that are listed as flammable-vapor-ignition resistant.”
• Section M1307.3.1, Protection From Impact: “Appliances shall not be installed in a location subject to vehicle damage except where protected by approved barriers.”
• Section M1307.1, General: “Installation of appliances shall conform to the conditions of their listing and label and the manufacturer's instructions. The manufacturer's operating and installation instructions shall remain attached to the appliance.”

The garage clauses name no fuel, so ask your building department how it applies them to a wood stove before you buy. The last clause is why the stove's manual decides: if it rules out a garage, or asks for clearances your garage cannot give, that stove is not the one for it.

Questions to Ask Your Building Department

• Do I need a permit for a wood stove and chimney in this garage, and an inspection before the first fire?
• Which edition of the code applies here, and with which local amendments?
• How do you apply Sections M1307.3 and M1307.3.1 to a wood stove?
• Does anything change because the garage is attached to the house, or because it is not?

Through the Wall or Through the Roof

Through the wall, the route this guide covers, uses one of our wood stove pipe kits through the wall. Only insulated Class A chimney pipe passes through the wall thimble. The stove pipe stays in the garage and joins the Class A pipe through a stove pipe adapter before the wall.

Outside, use 6 inch insulated chimney pipe for a stove with a 6 inch flue collar, or 8 inch chimney pipe for an 8 inch collar, unless the stove's manual gives a different chimney diameter.

A Class A chimney is factory-built, so where your state or town has adopted the IRC, Section R1005.1 applies: “Factory-built chimneys shall be listed and labeled and shall be installed and terminated in accordance with the manufacturer's installation instructions.”

Through the roof, our garage chimney kit through the roof takes Class A pipe up through the garage ceiling or roof, with a ceiling or roof support box, an attic insulation shield, and a roof flashing with storm collar that the kit builder matches to your roof pitch (flat, 1/12 to 6/12 or 7/12 to 12/12).

On either route, keep the stove's own clearances from its listing label and manual.

Keep single wall stove pipe at least 18 inches from combustible materials (IRC Table M1803.3.4); the installation instructions for our Class A system allow less only where a clearance reduction system your building department accepts is used or the stove is listed and its instructions give a different clearance.

Keep at least 2 inches between Class A pipe and anything combustible, as the installation instructions of the system installed set.

Why Use a Through-the-Wall Setup for a Garage?

Most garages lack an existing chimney or flue opening. Running a chimney pipe through the roof means penetrating roof framing, adding flashing, and dealing with potential leaks. A through-the-wall installation avoids all of that. The pipe exits horizontally through the wall via a thimble, connects to a tee, and then runs vertically along the outside of the building.

This approach works well for detached garages, workshops, and outbuildings where you want to heat with a wood stove but keep the installation as simple as possible. It is also easier to inspect and maintain because the entire vertical run is visible and accessible from outside.

For a detached garage, our kit for an external chimney brings the thimble, the tee, the base wall support, the brackets and the Class A sections together in one order.

If the garage could take the chimney either way, our comparison of a through-the-wall or through-the-roof chimney sets the two routes side by side, from draft to the parts each one needs.

What Components Do You Need?

A through-the-wall chimney kit includes everything for a complete installation. Here is what each component does:

Stove Pipe vs. Class A Chimney Pipe - Know the Difference

This is a common source of confusion. Stove pipe (also called connector pipe) is only rated for use inside the room, between the stove and the wall or ceiling. It must never pass through a wall, ceiling, or roof. Single-wall stove pipe requires 18 inches of clearance to combustibles; double-wall stove pipe requires the clearance on its listing label, typically 6 inches from combustible walls and 8 inches from ceilings.

Class A insulated chimney pipe is the only pipe type rated to pass through walls, ceilings, and roofs. It needs at least 2 inches of clearance to combustibles, as the installation instructions of the system installed set.

For a through-the-wall  chimney kit installation, Class A pipe is what goes through the wall (inside the thimble) and runs vertically on the outside. The stove pipe stays inside the garage and connects the stove to the Class A pipe through a stove pipe adapter, before the wall: stove pipe never enters the thimble.

Step-by-Step Installation

1. Check local building codes. Before you buy anything, contact your local building department. There is no single national building code in the U.S.: your state, county or town adopts its own, often with amendments, and the building department confirms what applies to your garage. Some areas require a permit and inspection. Review the building codes overview for more detail.
2. Choose your exit location. Pick a spot on the wall where the pipe will exit. Ideally, this is directly behind or near the stove to keep the indoor stove pipe run short. The exit point should be between wall studs. Drill a small pilot hole from inside to outside to confirm your placement.
3. Cut the wall opening. Use a reciprocating saw to cut the hole for the wall thimble. The opening must be large enough to maintain the required 2-inch clearance to any combustible framing around the thimble. Measure carefully: Table 1 on page 6 of the installation instructions for our Class A system gives the framing dimensions.
4. Install the wall thimble. From outside, put the outer half of the thimble in the opening and fix it to the outside wall. From inside, fit the inner half, with the round plate, so its shield slides into the shield of the outer half, and fix it to the inside wall. The thimble protects the combustible wall where the chimney passes through it. Secure it according to the manufacturer instructions.
5. Mount the wall support bracket and tee. Fit a Class A chimney section to the horizontal branch of the tee, with a locking band at that joint, long enough that the stove pipe adapter sits inside the garage at least 18 inches from a combustible wall for single wall stove pipe (for double wall stove pipe, the clearance on its listing label), and slide that section through the thimble from outside, so only Class A pipe passes through the wall. Then join the wall support bracket to the bottom of the tee, set it against the exterior wall directly below the tee, check that it is level and fix it to the wall, as pages 19 and 20 of the installation instructions set out. This bracket carries the full weight of the vertical chimney run. The tee connects the horizontal pass-through to the vertical pipe run, and the clean-out cap at the bottom allows you to remove ash and creosote.
6. Build the vertical chimney run. Stack Class A insulated chimney pipe sections above the tee. Lock each section with a locking band. Add wall straps every 4 to 6 feet to secure the pipe to the building; page 20 of the installation instructions for our Class A system sets the limit, wall brackets no more than 8 feet apart, with at least 2 inches of clearance to combustible materials.
7. Meet the height requirement (3-2-10 rule). Under the 3-2-10 rule from NFPA 211, as our Class A installation instructions set it out, the top of the chimney must be at least 3 feet above the highest point where it passes through the roof and at least 2 feet higher than any portion of a building within 10 feet. Even though the pipe runs along the outside wall, this rule still applies. Taller chimneys also produce better draft.
   • Through a roof overhang, frame for at least 2 inches of clearance and fit a roof flashing and storm collar, or cut away the overhang for a 2 inch clearance.
   • More than 5 feet above the top wall bracket or the roof flashing, the instructions require one extended roof brace. Only one may be used: the chimney may rise no more than 10 feet above the roofline or its highest rigid support and no more than 5 feet above the brace.
8. Install the rain cap. Place the rain cap (with spark arrestor) on the top section. This keeps rain, snow, and debris out of the flue.
9. Connect the stove pipe inside. Inside the garage, run stove pipe from the stove collar to the stove pipe adapter on the Class A pipe that comes through the wall thimble; the stove pipe itself stops before the wall. Keep this run as short and straight as possible. Remember: single-wall stove pipe needs 18 inches of clearance to combustibles; double-wall needs the clearance on its listing label.
10. Inspect and test. Before the first fire, double-check all clearances, locking bands, and support brackets, and if your building department requires an inspection, have it done first. Then light a small test fire to verify proper draft.

Common Challenges and Tips

• Cutting through tough siding. Cement board, brick, or metal siding can be difficult to cut. Use a diamond blade or carbide-tipped hole saw, and always drill a pilot hole first to confirm alignment from both sides.
• Wind exposure. Garages often sit in more exposed locations than the main house. Make sure wall straps are tight and consider adding an extra bracket if your area gets strong winds.
• Draft issues. Exterior chimney runs can be cooler than interior ones, which may reduce draft in very cold weather. A taller chimney run and the insulation built into Class A pipe help maintain draft, and a chase helps too: in areas with long spells of cold weather, the installation instructions for our Class A system recommend enclosing an outside chimney below the roof line in a chase, to help reduce condensation, creosote buildup and poor draft.
• Garage door clearance. Plan your exit point so the vertical pipe run does not interfere with the garage door track or swing path.

What Size Chimney Pipe Do You Need?

Follow your stove's manual for the pipe diameter. Most small to mid-size wood stoves use a 6-inch flue collar, which means you need 6-inch Class A chimney pipe. Larger stoves may need an 8-inch collar, requiring 8-inch Class A pipe. Never choose a chimney with an inside diameter smaller than your stove's outlet.

Related Installations

A through-the-wall garage installation follows the same basic principles as other exterior chimney setups. If you are working on a different building type, these guides may help:

• Installing a Class A chimney in a shed
• A greenhouse wood burning stove and its chimney
• Running a chimney flue along an outside wall
• Choosing the best Class A chimney pipes
• External Class A chimney pipe installation
• Pole barn wood stove installation, through the metal roof or the siding

Not Sure Which Kit or Size You Need?

Every garage is different - wall thickness, stove size, roof height, and local codes all affect what you need. Use our free chimney design service to get a custom recommendation within 24 hours. Just tell us your stove model, garage dimensions, and wall type, and we will put together a complete parts list. You can also call us at 888-834-0880 (9 AM - 9 PM, 7 days a week) or browse chimney liner kits and complete chimney kits to see what is available.

Frequently Asked Questions

Do You Need a Permit to Install a Chimney in a Garage?

Ask your local building department before starting. There is no single national building code: your state, county or town adopts its own, often with amendments, so permit requirements vary. Some areas also require a final inspection before you can use the stove. Check our building codes guide for an overview of the codes involved.

What Size Chimney Pipe Do You Need for a Garage Wood Stove?

Follow the stove's manual for the chimney pipe diameter, as the installation instructions for our Class A system say. Most small to mid-size garage wood stoves have a 6-inch collar. Larger stoves may use an 8-inch collar. Never reduce the diameter below the collar size: the installation instructions for our Class A system say never to choose a chimney with an inside diameter smaller than your appliance's outlet.

Can You Use Single-Wall Stove Pipe Through a Garage Wall?

No. Single-wall and double-wall stove pipe are only rated for use inside the room, between the stove and the wall penetration. Only Class A insulated chimney pipe (UL 103 HT listed) is rated to pass through walls, ceilings, and roofs. Using stove pipe through a wall is a serious fire hazard: our stove pipe pages say anything passing through a wall, ceiling or roof must be Class A insulated chimney pipe.

How Tall Does a Through-the-Wall Chimney Need to Be?

The chimney must meet the 3-2-10 rule from NFPA 211, as our Class A installation instructions set it out: at least 3 feet above the highest point where it passes through the roof and at least 2 feet higher than any portion of a building within 10 feet. A taller chimney produces better draft.

If it rises more than 5 feet above the top wall bracket or the roof flashing, the instructions require one extended roof brace; only one may be used, and the chimney may rise no more than 10 feet above the roofline or its highest rigid support and no more than 5 feet above the brace.

Need More Information?

Hopefully, you just got all the answers you need, but maybe you still have a question. If you want to know about this or any other topic relating to domestic burners and flue pipes, then please check out our FAQ page.

Here are our installation guides.

If you have a more specific problem, or you need your purchase sorted out quickly, then take advantage of our years of experience and head to our contact page.