The modern garage is frequently much more than the place you park the family car. Perhaps its also used as a workshop or has been converted to an extra family activity area, but a garage is commonly unheated and installing a woodstove can transform the functionality and enjoyment of the space for other uses.
Place the woodstove in the desired location, positioned according to the manufacturer's clearance and placement recommendations for both the stove unit and the required chimney assembly.
Access the ceiling from a stepladder, then use a plumb bob to locate and mark the centre of the stove's chimney connection flange on the garage ceiling. This will be the centre point of the chimney assembly's collar box.
Measure the outside dimensions of the chimney's ceiling collar box and layout these dimensions from the centre point marked in Step 2.
NOTE: Adjust the woodstove's position on the floor, as necessary, to keep the collar box centred between ceiling joists and the roof penetration a minimum of 2-inches from the roof rafters.
Cut the chimney collar box outline marked in Step 3 with a jab saw, then mount the collar box to the ceiling joists according to the manufacturer's specifications.
Mark the centre line of the chimney on the underside of the roof sheathing using a plumb bob centred through the ceiling collar box to the woodstove's chimney connection flange.
Drill a ¼-inch hole through the roof sheathing and roofing at the centre point marked in Step 5, using an electric drill mounted with a ¼-inch wood boring bit.
Go to the garage roof and locate the hole drilled in Step 6 and remove the roofing to a minimum radius of 8-inches around the drilled hole. Save the roofing for possible reinstallation over the chimney flashing.
Cut the chimney opening in the roof sheathing, using a jigsaw or reciprocating saw, to the diameter of the chimney plus 4-inches. Position the chimney flashing centred over the hole and secure according to the chimney manufacturer's specifications.
Replace the roofing over the chimney flashing as necessary to insure drainage and a watertight seal using roofing mastic, as needed, where the replaced roofing laps over the flashing metal.
Return to the garage and assemble the chimney pipe sections to a length sufficient to stack through the roof flashing installed in Step 8 when attached to the woodstove's connection flange. Insert the assembled chimney piping through the roof opening and flashing, then connect the assembled chimney base to the stove's connection flange following the manufacturer's instructions using the screws provided. Use a builders level to verify the chimney is plumb.
Go to the roof and add the remaining chimney sections and attach the chimney cap by snapping the cap's base over the locking tabs onto the top of the top chimney section.
Attach the chimney counter-flashing, called a "storm collar," over the roof flashing installed in Step 8 and secure by tightening the collar clamp's screw with a screwdriver.
Seal the storm collar by applying a continuous bead of caulking around the perimeter where the collar flashing's inside edge meets the chimney's vertical surface.
If your woodstove is not equipped with a rear heat shield, the adjacent wall surface will need to be covered with a non-combustible material.
National and local building and fire codes set requirements for the installation of woodstoves and chimneys and the materials specified in this project are superseded by those codes and the woodstove manufacturer's specifications. Consult your local building department to make certain your installation complies with all fire code requirements prior to undertaking this project.