There’s no denying that a fireplace adds character and ambience to a home’s
interior, but when the traditional coal- or wood-burning fireplace lost
its central- heating role to the automatic furnace, many homes went hearthless.
Retrofitting a traditional masonry fire place in most of those homes is
an expensive and complicated project, but a modular metal fireplace that
burns gas can provide a convincing substitute, without the need for a heavy,
expensive masonry chimney. Most units operate with the flick of a wall switch
or remote control, and optional blower units expand their heating ranges
by actively distributing heated air into the room.
Aside from their simpler, more affordable installation, direct-vent
gas fireplaces eliminate the need to haul firewood through the house
or clean out ashes, and more flexibility in locating the unit. The
insulated metal duct that exhausts hot gases and brings in combustion
air can usually be installed through either an exterior wall or the
1. After mocking up the fireplace in several locations or
test-fitting the unit itself, use framing lumber to construct
a base platform the same size as the fireplace module. Fit a
3/4-in. ply wood top onto the base and fasten it with screws.
Slide it temporarily into position to check the fit against the
wall or corner.
2. With the necessary sealant, which is typically a stove
cement, rope gasket or high- temperature silicone caulk, fit
the first vent- pipe section in place. Fasten it securely according
to the instructions and add the next fitting. In this installation,
it’s a 9Q0 elbow with a straight pipe extension on the back end.
3. Mark an outline of the vent pipe on the wall surface and temporarily move the fire place out of the way. Cut a 12-in.
(30-cm) square opening around the vent-pipe location; add blocking and a header around the opening. If a wall stud obstructs the
path, cut a larger opening to alter the framing, as shown in
| 4. Drill holes at the corners of the square vent opening, penetrating
the exterior wall sheathing and siding. This transfers the opening
to the outer face of the wall so you can cut through the siding and sheathing. Next, fit the outer fire-stop and cap against the
siding and trace the outline; cut through only the siding.
5. Replace the wall insulation and patch the interior wall
surface—a rough patch is fine if you’ll add a fireplace surround and mantle to cover the area. Apply a bead of caulk around the
patch and around the perimeter of the vent opening; press the
interior fire-stop into the caulk and fasten it to the wall with
| 6. Move the fireplace unit into position and insert the interior
vent pipe through to connect with the exterior fire-stop. The procedure
for making the vent-pipe connection can vary with the manufacturer and model, so follow the instructions provided. Seal around the
vent pipe with a bead of high-temperature silicone caulk.
7. Slide the exterior vent fitting (a combination
fire-stop and cap) onto the pipe coming through the wall. If
necessary, install a metal drip cap under the siding, as shown
here, and use screws to fasten the fire-stop flange to the wall.
Use caulk to seal the joints between the siding and the metal
8. After installing the required gas and electrical
lines (we suggest you hire pros for this), level and fasten the
wood platform. Using the illustration at far right as a guide,
frame the remaining structure for the fireplace surround. The
detailing can vary from the example shown, as long as you provide
a nailing base for the drywall.
9. The mantle frame is the next assembly required to complete
the structural framework for the fire place surround. Slide it
into position atop the main façade frame and fasten it with screws.
Follow this step by installing the angled frame pieces at each
end; then build and install the hearth extension and upper wall
10. Cut the column parts from
2x10 and 2x2 stock and screw them to the lower wall frame of
the surround. Note that the vertical 2x2 cleats taper to a point
at their lower end and that the lower 2x10 block is beveled
45° on its upper edge. When complete, fasten drywall over the entire
11. Cover all the outside corners with metal
drywall corner bead. Where two or more corner beads meet, cut
angles at the ends to form a point so the flanges don’t interfere
with each other. Nail the bead tight with drywall nails. For
corners greater than 90°, install a special 120° metal
|12. At inside corners, embed paper drywall tape in joint compound and apply the compound to all surfaces to cover the joints and corner bead. Let dry; then sand and repeat one or two applications
until joints and surfaces are smooth and flat. If desired, apply
a troweled or sponged texture, prime and paint.
Fireplace surround details (image, right). This
illustration reveals the basic framing components of the fireplace
surround, mantle and hearth. Make certain to follow the manufacturer’s
guidelines, which specify safe clearances from combustible materials.
No-vent Gas Fireplaces
No-vent, or vent-free, gas fireplaces represent the simplest route to
getting a fireplace, but they aren’t legal everywhere because of air-quality
concerns. Like a gas kitchen range, they burn natural gas or propane and do it so cleanly that the tiny amounts of combustion by-products
generated don’t require a vent. These units have an oxygen-depletion
sensor that automatically shuts the gas off if the oxygen level in the
room falls below 18 percent; many also integrate carbon-monoxide detectors.
Air circulates around the firebox by natural convection, but the heat
output is modest