How to Install a Gas Fireplace

Complete DIY instructions for installing a direct-vent gas fireplace

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Enjoy the comfort and ambiance of a crackling fire on a cold winter's night. Here we'll show you how to install a gas fireplace. Don't worry about installing a chimney. You don't need one. You simply vent the fireplace out the side of the house. Once the fireplace is installed, you just flip a switch to start a roaring fire.

Tools Required

  • Brad nail gun
  • Caulk gun
  • Circular saw
  • Cordless drill
  • Drill bit set
  • Drywall sander
  • Drywall saw
  • Dust mask
  • Hammer
  • Hearing protection
  • Knee pads
  • Knockdown knife
  • Level
  • Mud pan
  • Paintbrush
  • Rasp
  • Roller sleeve
  • Roller tray
  • Sanding block
  • Sanding pole
  • Screw gun
  • Socket/ratchet set
  • Straightedge
  • Stud finder
  • T-square
  • Tape measure
  • Tin snips
  • Utility knife

Materials Required

  • 1/2x48x96 drywall
  • 100-grit sandpaper
  • 2x10x12' lumber (2)
  • 3/4x4x4' plywood
  • 9" vent pipe
  • Acrylic caulk
  • Corner beads
  • Gas fireplace
  • Heat shield flashing
  • Interior firestop
  • Joint compound
  • Metal drip cap
  • Metal nail plates
  • Paint or textured finished
  • Polyurethane caulk
  • Silicone caulk
  • Straight pipe

Choosing a Gas Fireplace

It’s hard to beat a crackling wood fire on a chilly night. But modern gas fireplace come pretty close, and without the drawbacks of wood. Not only does gas burn much cleaner, making it a better choice for the environment, but there are no messy logs to carry through the house or ashes to clean out. And lighting the fire is as simple as flicking a switch or turning a valve.

A direct-vent gas fireplace doesn’t need a chimney. Rather, you can run a special vent to the outside through an exterior wall. This process is simple and fire-safe as long as you follow the manufacturer’s directions. Be sure to read them carefully, because they might differ slightly from what we show here. For fire safety, however, make sure to heed the manufacturer’s directions on clearances for combustibles.

Cost to Install a Gas Fireplace

Wondering how much does it cost to install a gas fireplace? If you have some carpentry and drywalling experience, you shouldn’t have any trouble finishing this project. The fireplace will take you about a day to install. Then plan to spend an entire weekend framing and installing drywall and a few hours each day for the rest of the week troweling on additional coats of joint compound. The following weekend you can prime the walls and apply the texture.

  • The direct-vent fireplace and vent parts we purchased cost us about $1,800. For $650 more, our fireplace dealer would have installed the fireplace, not including the gas and electric hookups or any interior finishing.
  • The materials for the wood framing, drywall and stucco coating cost an additional $175. Hire a plumber to run the gas line during the framing process and connect it to the fireplace ($250 to $500).

In addition to a basic set of hand tools, you’ll need a circular saw and a drill. A power miter box is handy but not necessary for cutting the angles on the framing parts. You’ll need a tin snips for cutting the metal corner bead, a collection of taping knives (2-in., 4-in., 6-in. and 12-in.) and a mud pan for applying the joint compound and texture.

Shopping for a Gas Fireplace

The fireplace we’re using, and the type we recommend, is a direct-vent fireplace. This type draws air from outdoors to feed the flame. Not only is this setup more efficient because you’re not losing valuable heated air up the chimney, it’s safer too because it greatly reduces the possibility of dangerous carbon monoxide backing up into your home.

The best place to shop for fireplaces is at fireplace dealers that have showrooms with working models on display. You’ll be able to see how the artificial logs look when they’re burning and pick a fireplace style you like.

Make Sure You Have Proper Venting

Adding a fireplace to a house is a complex project, but you can do it yourself. Proper ventilation is essential for a safe-operating fireplace.

Project step-by-step (22)

Step 1

Build a Mockup To Find the Best Position

Mock up the fireplace using the dimensions given in fireplace brochures and outline the hearth shape with masking tape. Your new fireplace will have a major impact on your room. Build a simple mock-up to get a feel for the amount of space it takes up and to see how the angled placement will affect furniture arrangement and traffic patterns.

When you’re satisfied with the aesthetics of the fireplace, turn your attention to the mechanical requirements. You’ll need to run a gas supply line for the fireplace. Call in a plumber to plan the route before you order the fireplace.

Most gas fireplaces don’t require electricity to operate. However, if you ever decide to add a blower to increase heat output or a hand-held remote control, you’ll have to connect the fireplace to an available electrical circuit, so run a wire to the fireplace while it’s accessible.

In addition, since electrical codes don’t allow you to simply cover a box that contains live wires, you’ll have to disconnect or relocate any boxes or receptacles that will be covered by the new fireplace.

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Step 2

Get the Gas, Electrical and Vent in Place First

Determine how you’ll get the vent from the fireplace to the outdoors. Thanks to the ingenious two-layer design that keeps the outside of the pipe relatively cool, the vents from direct-vent fireplaces can run straight out through the wall or up through the roof, allowing great flexibility in design and placement of the fireplace. Even so, there are very specific requirements that your fireplace and vent installation must meet. Check the installation manual to make sure. Here are a few key points to look for:

  • Clearances from the fireplace box to surrounding walls and to the wood framing. Ours required 1/2 in. on the sides and back and 3-1/2 in. on top.
  • Distance the vent must be kept from insulation, wood and other combustibles. Sometimes metal shields must be used over the top of the vent to divert the heat.
  • Maximum number of bends in the vent pipes and the relationship of horizontal to vertical lengths of pipes. Our manual had many illustrations with dimensions to help with the venting layout. You can ask the dealer for help with vent design.
  • Distance the vent cap must be kept from windows, doors, corners and other elements at the point where it leaves the house. Measure where the vent pipe will come out and make sure it meets the specifications.
  • And before you begin, contact the local building inspections department to obtain the permits required for a fireplace installation.

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