Division B
Acceptable Solutions

Part 9 — Housing and Small Buildings

Section 9.21. Masonry and Concrete Chimneys and Flues

9.21.1. General

9.21.1.1. Application

1) This Section applies toI

a)rectangular masonry or concrete chimneys not more than 12 m in height serving fireplaces or serving appliances having a combined total rated heat output of 120 kW or less, and

b) flue pipes connected to such chimneys.

2) Chimneys, other than those described in Sentence (1), gas vents and flue pipes serving gas-, oil- or solid-fuel-burning appliances and their associated equipment, including stoves, ranges and space heaters, covered by the standards referenced in Sentences 9.33.5.2.(1) and 9.33.5.3.(1), shall conform to Subsection 9.33.10.I

3) Chimneysand flue pipes other than those described in Sentences (1) and (2) shall conform to Section 6.3.I

9.21.1.2. Chimney or Flue Pipe Walls

1) The walls of any chimney or flue pipe shall be constructed so as to be smoke- and flame-tight.I

9.21.2. Chimney Flues

9.21.2.1. Chimney Flue Limitations

1) A chimney flue that serves a fireplace or incinerator shall not serve any other appliance.I

2) A chimney flue that serves a solid-fuel-burning appliance shall not be connected to a natural-gas- or propane-fired appliance.I

3) A chimney flue that serves a solid-fuel-burning appliance shall not be connected to an oil-burning appliance unless the solid-fuel-burning appliance is certified for such installation and the installation of both appliances meets the requirements of the relevant standards referenced in Article 9.33.5.2.I

9.21.2.2. Connections of More Than One Appliance

1) Except as required by Article 9.21.2.1., where two or more fuel-burning appliances are connected to the same chimney flue, the connections shall be made as described in Sentences (2) to (4) and an adequate draft shall be provided for the connected appliances in conformance with the requirements of applicable regulations or standards referenced in Subsection 9.33.10. I

2) Where 2 or more fuel-burning appliances are connected to the same chimney flue, the appliances shall be located on the same storey.I

3) The connection referred to in Sentence (2) for a solid-fuel-burning appliance shall be made below connections for appliances burning other fuels.I

4) The connection referred to in Sentence (2) for a liquid-fuel-burning appliance shall be made below any connections for appliances burning natural gas or propane.I

9.21.2.3. Inclined Chimney Flues

1) Chimney flues shall not be inclined more than 45° to the vertical.I

9.21.2.4. Size of Chimney Flues

1) Except for chimneys serving fireplaces, the size of a chimney flue shall conform to the requirements of the appliance installation standards referenced in Sentences 9.33.5.2.(1) and 9.33.5.3.(1).I

2) Where a chimney flue serves only one appliance, the flue area shall be at least equal to that of the flue pipe connected to it.I

9.21.2.5. Fireplace Chimneys

1) The size of a chimney flue serving a masonry fireplace shall conform to Table 9.21.2.5.A or Table 9.21.2.5.B.I

Table 9.21.2.5.A
Diameter of Round Flues for Fireplace Chimneys
Forming Part of Sentence 9.21.2.5.(1)
Fireplace Opening,
m2		 Chimney Height, m
3.0 to 4.5
 > 4.5 to 5.9
 > 5.9 to 8.9
 > 8.9 to 12
Flue Diameter, mm
min. max. min. max. min. max. min. max.
up to 0.150 110 170 100 160 90 150 90 150
0.151 to 0.250 150 210 130 190 130 190 120 180
0.251 to 0.350 180 240 160 220 150 210 140 200
0.351 to 0.500 220 280 200 260 190 250 170 230
0.501 to 0.650 260 320 230 290 220 280 200 260
0.651 to 0.800 290 350 260 320 240 300 220 280
0.801 to 1.00 330 390 290 350 270 330 250 310
1.01 to 1.20 360 420 320 380 300 360 270 330
1.21 to 1.40 390 450 350 410 330 390 300 360
1.41 to 1.60 420 480 380 440 350 410 320 380
1.61 to 1.80 — — 400 460 370 430 340 400
1.81 to 2.00 — — — — 400 460 360 420
2.01 to 2.20 — — — — — — 380 440
Table 9.21.2.5.B
Rectangular Flue Sizes for Fireplace Chimneys
Forming Part of Sentence 9.21.2.5.(1)
Fireplace
Opening, m2		 Chimney Height, m
3.0 to 4.5 > 4.5 to 5.9 > 5.9 to 8.9 > 8.9 to 12
Flue Size, mm
min. max. min. max. min. max. min. max.
up to 0.150 200 x 200 200 x 200 100 x 200 100 x 200 100 x 200 100 x 200 100 x 200 100 x 200
0.151 to 0.250 200 x 200 200 x 200 200 x 200 200 x 200 200 x 200 200 x 200 200 x 200 200 x 200
0.251 to 0.350 200 x 300 200 x 300 200 x 200 200 x 300 200 x 200 200 x 200 200 x 200 200 x 200
0.351 to 0.500 300 x 300 300 x 300 200 x 300 200 x 300 200 x 300 200 x 300 200 x 200 200 x 300
0.501 to 0.650 300 x 300 300 x 400 300 x 300 300 x 300 300 x 300 300 x 300 200 x 300 200 x 300
0.651 to 0.800 300 x 400 300 x 400 300 x 300 300 x 400 300 x 300 300 x 300 300 x 300 300 x 300
0.801 to 1.00 400 x 400 400 x 400 300 x 400 300 x 400 300 x 400 300 x 400 300 x 300 300 x 300
1.01 to 1.20 400 x 400 400 x 400 400 x 400 400 x 400 300 x 400 300 x 400 300 x 400 300 x 400
1.21 to 1.40 — — 400 x 400 400 x 400 400 x 400 400 x 400 300 x 400 300 x 400
1.41 to 1.60 — — — — 400 x 400 400 x 400 400 x 400 400 x 400
1.61 to 1.80 — — — — — — 400 x 400 400 x 400
1.81 to 2.00 — — — — — — 400 x 400 400 x 400
9.21.2.6. Oval Chimney Flues

1) The width of an oval chimney flue shall be not less than two-thirds its breadth.I

9.21.3. Chimney Lining

9.21.3.1. Lining Materials

1) Every masonry or concrete chimney shall have a lining of clay, concrete, firebrick or metal.I

9.21.3.2. Joints in Chimney Liners

1) Joints of chimney liners shall be sealed to provide a barrier to the passage of flue gases and condensate into the cavity between the liner and the surrounding masonry.I

2) Joints of clay, concrete or firebrick chimney liners shall be struck flush to provide a straight, smooth, aligned chimney flue.I

9.21.3.3. Clay Liners

1) Clay liners shall conform to CAN/CSA-A324-M, “Clay Flue Liners.”I

2) Liners referred to in Sentence (1) shall be not less than 15.9 mm thick and shall be capable of resisting, without softening or cracking, a temperature of 1 100°C.I

9.21.3.4. Firebrick Liners

1) Firebrick liners shall conform to ASTM C 27, “Classification of Fireclay and High-Alumina Refractory Brick.”I

2) Firebrick liners shall be laid with high temperature cement mortar conforming to CAN/CGSB-10.3, “Air Setting Refractory Mortar.”I

9.21.3.5. Concrete Liners

1) Concrete flue liners shall conform to Clause 4.2.6.4. of CAN/CSA-A405-M, “Design and Construction of Masonry Chimneys and Fireplaces.”I

9.21.3.6. Metal Liners

1) Metal liners shall be constructed of not less than 0.3 mm thick stainless steel.I

2) Metal liners referred to in Sentence (1) shall only be used in chimneys serving gas- or oil-burning appliances. (See Appendix A.)I

9.21.3.7. Installation of Chimney Liners

1) Chimney liners shall be installed when the surrounding masonry or concrete is placed.I

9.21.3.8. Spaces between Liners and Surrounding Masonry

1) A space not less than 10 mm wide shall be left between a chimney liner and surrounding masonry.I

2) The space required in Sentence (1) shall not be filled with mortar.I

9.21.3.9. Mortar for Chimney Liners

1) Chimney liners used in chimneys for solid-fuel-burning appliances shall be laid in a full bed ofI

a)high temperature cement mortar conforming to CAN/CGSB-10.3, “Air Setting Refractory Mortar,” or

b)mortar consisting of 1 part Portland cement to 3 parts sand by volume.

2) Chimney liners used in chimneys for oil- or gas-burning appliances shall be laid in a full bed of mortar consisting of 1 part Portland cement to 3 parts sand by volume.I

9.21.3.10. Extension of Chimney Liners

1) Chimney liners shall extend from a point not less than 200 mm below the lowest flue pipe connection to a point not less than 50 mm or more than 100 mm above the chimney cap.I

9.21.4. Masonry and Concrete Chimney Construction

9.21.4.1. Unit Masonry

1) Unit masonry shall conform to Section 9.20.I

9.21.4.2. Concrete

1) Concrete shall conform to Section 9.3.I

9.21.4.3. Footings

1) Footings for masonry chimneys and concrete chimneys shall conform to Section 9.15.I

9.21.4.4. Height of Chimney Flues

1) A chimney flue shall extend not less thanI

a)900 mm above the highest point at which the chimney comes in contact with the roof, and

b)600 mm above the highest roof surface or structure within 3 m of the chimney.

(See Appendix A.)
9.21.4.5. Lateral Stability

1) Except as provided in Sentence (2), chimneys shall be braced in accordance with Subsection 4.3.2. to provide lateral stability under wind loads.I

2) A chimney need not be laterally braced providedI

a)no horizontal outside dimension is less than 400 mm, and

b)the chimney extends not more than 3.6 m above a roof or the masonry wall of which it forms a part.

(See Appendix A.)
9.21.4.6. Chimney Caps

1) The top of a chimney shall have a waterproof cap of reinforced concrete, masonry or metal.I

2) The cap required in Sentence (1) shall slope from the lining and be provided with a drip not less than 25 mm from the chimney wall.I

3) Cast-in-place concrete caps shall be separated from the chimney liner by a bond break and be sealed at that location.I

4) Jointed precast concrete or masonry chimney caps shall have flashing installed beneath the cap extending from the liner to the drip edge.I

9.21.4.7. Cleanout

1) A cleanout opening with a metal frame and a tight-fitting metal door shall be installed near the base of the chimney flue.I

9.21.4.8. Wall Thickness

1) The walls of a masonry chimney shall be built of solid units not less than 75 mm thick.I

9.21.4.9. Separation of Flue Liners

1) Flue liners in the same chimney shall be separated by not less than 75 mm of masonry or concrete exclusive of liners where clay liners are used, or 90 mm of firebrick where firebrick liners are used.I

2) Flue liners referred to in Sentence (1) shall be installed to prevent significant lateral movement.I

9.21.4.10. Flashing

1) Junctions with adjacent materials shall be adequately flashed to shed water.I

9.21.5. Clearance from Combustible Construction

9.21.5.1. Clearance from Combustible Materials

1) The clearance between masonry or concrete chimneys and combustible framing shall be not less thanI

a)50 mm for interior chimneys, and

b)12 mm for exterior chimneys.

(See Appendix A.)

2) A clearance of not less than 150 mm shall be provided between a cleanout opening and combustible material.I

3) Combustible flooring and subflooring shall have not less than a 12 mm clearance from masonry or concrete chimneys.I

9.21.5.2. Sealing of Spaces

1) All spaces between masonry or concrete chimneys and combustible framing shall be sealed top or bottom with noncombustible material.I

9.21.5.3. Support of Joists or Beams

1) Joists or beams may be supported on masonry walls which enclose chimney flues provided the combustible members are separated from the flue by not less than 290 mm of solid masonry.I