Step 3.
To install the round support box/wall thimble cover in a flat ceiling, cut a 229 mm square hole in the ceiling, centered on the hole drilled in Step 2. Frame the hole as shown in Figure 7.22.
CEILING JOISTS
SHINGLES OVERLAP ON TOP EDGE OF FLASHING
FRAMING
229 mm x 229 mm 
ROUND CEILING SUPPORT BOX/WALL THIMBLE COVER
CAP AND STORM COLLAR NOT SHOWN FOR CLARITY
Figure 7.23
Step 7.
40 mm LONG 
WOOD SCREWS
Figure 7.22
Step 4.
Assemble the desired lengths of pipe and elbows neces- sary to reach from the gas stove up through the round sup- port box. Ensure that all pipe and elbow connections are in their fully
Step 5.
Cut a hole in the roof centered on the small drill hole placed in the roof in Step 2. The hole should be of sufficient size to meet the minimum requirements for clearance to com- bustibles, as specified. Continue to assemble lengths of pipe and elbows necessary to reach from the ceiling support box/wall thimble up through the roof line. Galva- nized pipe and elbows may be utilized in the attic, as well as above the roofline. The galvanized finish is desirable above the roofline, due to its higher corrosion resistance (compared to black pipe).
NOTE:
(1) If an offset is necessary in the attic to avoid obstruc- tions, it is important to support the flue pipe every 91.4cm to avoid excessive stress on the elbows, and possible separation. Wall straps are available for this purpose, Figure 7.10, page 15.
(2)Whenever possible, use 45° elbows, instead of 90° elbows. The 45° elbow offers less restriction to the flow of flue gases and intake air.
Step 6.
Slip the flashing over the pipe section(s) protruding through the roof. Secure the base of the flashing to the roof with roofing nails. Ensure the roofing material over- laps the top edge of the flashing as shown in Figure 7.23. Verify that the chimney is the required height above the roof. See roof pitch table, Figure 4.3.
Continue to assemble pipe sections until the height of the flue (before adding the termination cap) meets the mini- mum local code requirements. Note that for steep roof pitches, the flue height must be increased. See Roof Pitch Table (Figure 4.3). In high wind conditions, nearby trees adjoining rooflines, steep pitched roofs, and other similar factors can result in poor draft, or down drafting. In these cases increasing the flue height or switching to the high wind termination cap may solve this problem.
Step 8.
Slip the storm collar over the pipe, and push it down to the top of the flashing (Figure 7.24). Use
SECURE FLASHING WITH
AND ROOFING NAILS
Figure 7.24
Heat & Glo • | 35 |
