Click image to enlarge.
1. Mock up the fireplace using the dimensions given
in fireplace brochures and outline the hearth shape with masking
tape.
Click image to enlarge.
2. Cut 2x10s and nail them together to create an
11-1/2 in. tall platform the shape of the fireplace. Nail 2x4 cleats to the
bottom. Cut 3/4-in. plywood to fit and screw it to the top.
3. Set the fireplace on the platform and slide it
into position. Then apply a pencil-width bead of sealant to the starting collar
of the fireplace. Use the sealant recommended by the manufacturer, usually
stove cement or high-temperature silicone caulk.
Click image to enlarge.
4. Slide the first vent pipe over the
starting instructions. If your fireplace requires a gasket collar and lock it
in place according to the to seal the joint between the vent and fireplace,
make sure it’s properly positioned. (Ours required the braided rope
gasket shown.)
5. Connect the 90-degree
elbow and a 9-in. straight section to the first vent pipe. They should meet the
exterior wall at a 90-degree angle. Trace a circle around the pipe on the wall.
Using the interior firestop for reference, mark a 12-in. square on the wall.
Our square is centered 1 in. above the center of the vent
pipe.
6. Cut out 12-in. square the
hole with a drywall saw and look for obstructions. If there’s a wall stud
in the way, cut out the drywall between the two closest studs and about 9 in.
above the square opening. Caution: Keep the saw blade shallow to avoid cutting
hidden electrical wires.
7. Cut out the wall stud and
add a double 2x6 header. Support the header with trimmers screwed to the
existing studs. Notch for electrical cables if necessary. (A metal nail plate
is required if the cable is closer than 1-1/4 in. to the face of the framing.)
Frame the 12-in. opening. Drill a 3/8-in. hole through the wall at each corner
to transfer the location of the opening to the outside.
8. Connect the four holes
with lines and cut out the 12-in. opening in the siding and sheathing. Mark
another square opening the size of your exterior firestop and cap, and cut
through the siding only. Finish the corners with a utility knife or chisel.
Vinyl, aluminum, stucco and brick siding require different
techniques.
9. Replace the insulation and drywall, reusing the
old piece if possible. Seal the drywall seams with caulk and place a bead of
caulk around the opening. Press the interior firestop into the caulk and screw
it to the wall.
10.Complete the vent by sliding a section of pipe
through the firestop from the outside. In our case this pipe was part of the
telescoping exterior firestop and cap. Then seal the gap between the vent and
the interior firestop with high-temperature silicone caulk.
11. Slide the combination firestop and vent
termination into the telescoping section. Screw the firestop to the wall and
seal it with caulk. If your cap has a built-in drip cap that prevents you from
sliding it in, cut it off and slide a prebent drip cap under the siding as
shown.
