How to Install a Direct Vent Fireplace Flue

fireplace in the corner of a room
  • 5-10 hours
  • Advanced
  • 200-3,000
What You'll Need
7 inch pipe
4 inch pipe
90 degree elbow
24 inch vertical direct vent pipe
Wall thimble collar
Wood molding
Horizontal vent cap
Drywall saw
Safety goggles
Gasket cement

Installing the flue is one of the most important jobs when you plan to install a direct vent fireplace. It’s basically the venting system of the fireplace, composed of a dual-walled pipe, or a pipe within another pipe. Let's find out the installation process of the flue.

Step 1 - Observe Building Codes

stamp of approval on blueprint

Go to your local building department and verify the codes and regulations of building a fireplace in your area. Make sure that you follow the prescribed specifications of your local laws, in order to avoid problems and complications in the future, and obtain the proper building permits for your direct vent fireplace.

Step 2 - Horizontal or Vertical

Now you have to decide which type of direct vent fireplace you would prefer. You can go with a horizontal flue, wherein the vent goes through a wall to the outside, or a vertical flue, where the vent goes up through the roof like a chimney. Use whatever works best for you, depending on the available space in your house and where you want to situate your fireplace.

Step 3 - Purchase the Appropriate Kit

Each kit comes with different materials. For the purpose of this article, let’s assume you chose a horizontal vent. This kit will usually come with a 90-degree elbow, 24-inch direct vent pipe, adjustable pipe, wall thimble collar and a horizontal vent cap.

Step 4 - Install

wood stove burning in a cabin

Use the 90-degree elbow’s frame as a guide to make a corresponding hole in your wall for your fireplace vent. Make a mark where you want to make a hole in your wall by tracing an outline of the edges of the elbow. With the mark as your guide, drill four holes at the corners then use the drywall saw starting from one corner going to the next, until the hole for your direct vent fireplace is accomplished. Finish by securing some wood molding onto the sides of the square hole you just made, making a frame to make it tidier. Place the appropriate sized wooden boards on the inside of the hole, drill some holes on them and secure them with screws. This is in order to establish a more secure and smoother frame and not have a rough cutout to fasten your kit into. Making the hole on the exterior surface of the wall will depend on the finish or siding you have.

Step 5 - Connect the Pipes to the Wall

Once the hole has been created and framed, place the four-inch pipe inside the seven-inch pipe, and attach them to the port at the top or rear of the fireplace. Also, attach the elbow to the hole by screwing it to the wall. Make sure it is aligned with the hole. Direct the two concentric pipes to the elbow and it should go right through snugly. Connect the pipes outside as well, directing them up to the roof. Place weatherproof caulking around the vent coming through the wall to provide a weathertight seal.

Step 6 - Install the Vent Cap

Once you have already made this connection, install the vent cap outside. Fit the vent cap over the pipe going up to the roof and screw it safely. Be sure that it is securely fastened. Use some heat-resistant gasket cement to put on the sides of the vent cap in order to prevent rain or snow from coming in. Your direct vent fireplace should now be ready for use.