How to Install a Gas Fireplace

Complete DIY instructions for installing a direct-vent gas fireplace

Get started building the 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.

Here we'll show you how to install a direct-vent gas fireplace and run the combination intake and exhaust vent directly through the exterior wall. Then we'll show you how to frame, drywall and texture the surround shown here. The surround is a fanciful combination of wood, drywall and special texturing. The design itself is traditional, but you can freely modify it. For fire safety, however, make sure to heed the manufacturer's directions on clearances for combustibles.

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.

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.

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Build a mock-up to find the best position

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 (Photo 1).

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.

Finally, 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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Get the gas, electrical and vent in place first

With the preliminaries out of the way, here's how you proceed. First order the fireplace and vent parts. When you know the delivery date, schedule the plumber and electrician to show up a few days later. This will give you time to accurately lay out the fireplace location on the floor, build the platform and run the vent. After the gas line and wiring are done and all inspections are completed, you'll build the frame, cover it with drywall, and complete the taping and decorating. Photos 2-5 show how to start the framing.

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Punching through the wall is the tough part

Photos 6-11 show how to finish building the platform and connect the vent and run it through the wall. If you don't run into obstructions when you cut the 12-in. hole (Photo 6), you won't have to remove any more drywall. Just frame around the opening with short pieces of lumber slid through the hole and held in place with screws through the drywall. Photos 7 and 8 show how to install the vent cap in a wall with wood siding. If your house has vinyl siding, cut it with a utility knife If it has aluminum or steel siding, use a tin snips or metal-cutting blade. Cover the ends of the siding with vinyl or metal J-bead (available at siding dealers) and install the drip cap (Photo 11) before you slide the vent cap into the hole. If your exterior is stucco, follow the same procedure, except drill the four holes from the inside with a masonry bit. Then use a masonry blade ($5 at a hardware store) in your circular saw to cut the stucco and a regular blade to cut the wood sheathing underneath. If you have a brick exterior, cut it with a masonry blade or brick chisel. Cut only the 12 x 12-in. hole and use plastic anchors and screws to mount the vent cap directly over the brick. Seal around it with urethane caulk. Ask your fireplace dealer if you need a special cap and firestop for brick walls.

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Construct the surround

When the venting is complete, double-check to make sure the fireplace unit is in the right place and construct the surround (Photos 13 – 17). Maintain the required clearance (check the instructions) between the fireplace and wood framing. We left 1/2-in. spaces on the sides and 3-1/2 in. on the top. Our vent required at least a 1-in. distance from combustible materials. If your fireplace is a different size from ours, you'll have to adjust the wood framing dimensions.

Cut out a section of drywall and screw wood blocking between the studs if there are no studs to connect the new framing to (Photo 12).

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Patience is the key, so be fussy for this drywall job

If you don't own a drywall screw gun, rent one for this job (about $25 per day). A 4-ft. drywall T-square, available at home centers and hardware stores for about $15, will speed up the cutting process. Before starting on the corner bead, use a Surform rasp tool to cut back protruding drywall edges.

With this rather complex design, covering all the outside corners with metal corner bead is an intricate job. Expect to spend the better part of a day finishing it. Pay close attention to details like keeping horizontal lines level and straight, vertical lines perfectly plumb and spacing between parallel metal beads even. Where several beads converge in a corner, the goal is to end up with one sharp point. Do this by snipping sharp pointed arrows on the ends of the beads, cutting them to the exact length and accurately lining up the points.

Even after nails are driven home, you can still make minor adjustments to the corner beads' alignment by bending the nail one way or another with a nail set. Buy 120-degree metal bead for angles greater than 90 degrees and special fillable L-bead to finish the drywall edge against the fireplace. You'll have to staple the L-bead to the drywall above the fireplace and rely on the joint compound to hold it in place.

It's all downhill after the corner bead is done. Cover the inside corners and joints with paper drywall tape embedded in joint compound. Then fill the slight valleys between the metal edges of the bead with joint compound (Photo 19). Because of shrinkage, the taping and filling process requires at least three coats, with drying time in between, so be sure to allow a few days to finish.

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Premixed texture make you feel like a master plasterer

We decided to apply a sandy, plaster-like finish to the drywall on our fireplace. There are a dozen ways to accomplish this look. We chose an acrylic-based product manufactured by USG that's typically used as an exterior finish. The USG Exterior Textured Finish is available in five textures, from fine to coarse, and 25 standard colors. A premixed 5-gallon pail costs about $45 and is more than enough for a project like this. To find acrylic texture finish like this, check the Yellow Pages or online for a drywall or stucco supply dealer in your area. You can also get special corner beads from the dealer.

Troweling on the texture is a messy operation, so mask off the walls and floor and put on some old clothes before you start. First prime the walls with a top-quality drywall primer. When the primer is dry, use a wide trowel to spread a thin layer of the premixed texture over an entire section, stopping at a breaking point like a corner. Next you'll float the area to impart texture and smooth out the trowel marks. If you're working in hot, dry conditions, start floating immediately. Otherwise you may have to let the texture mix set up for a few minutes. You'll have to experiment a little to see what works. We used a square of extruded polystyrene foam insulation to float the texture, but a grout float, wooden block or hard plastic trowel also will work.

Each tool gives a little different texture. Practice on a large scrap of drywall to get a feel for the material and refine your floating technique. Work from the top down to avoid splattering on completed texture.

Clean up the spills and splatters before they dry and occasionally clean your tools and float in a bucket of water to avoid a buildup of dry texture mix. If you do mess up a section, it's no big deal—just scrape it all off before it dries and start over with fresh texture mix. When the texture is dry, usually overnight, you can assemble the log set and light the fireplace. Follow the manufacturer's instructions for the exact procedure. If necessary, ask the plumber to help you light the pilot and fire up the burner. The smell of burning oil will go away once the factory residue burns off.

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.

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Additional Information

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