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) Intent StatementThis Section applies to
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) Intent StatementChimneys, 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, change begincooktops, ovenschange end 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.
3) Intent StatementChimneys and flue pipes other than those described in Sentences (1) and (2) shall conform to Section 6.3.
9.21.1.2. Chimney or Flue Pipe Walls
1) Intent StatementThe walls of any chimney or flue pipe shall be constructed so as to be smoke- and flame-tight.

9.21.2. Chimney Flues

9.21.2.1. Chimney Flue Limitations
1) Intent StatementA chimney flue that serves a fireplace or incinerator shall not serve any other appliance.
2) Intent StatementA chimney flue that serves a solid-fuel-burning appliance shall not be connected to a natural-gas- or propane-fired appliance.
3) Intent StatementA 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.
9.21.2.2. Connections of More Than One Appliance
1) Intent StatementExcept 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 provincial or territorial regulations or municipal bylaws or, in the absence of such regulations or bylaws, with the requirements of the relevant standards listed in Subsection 9.33.10.
2) Intent StatementWhere 2 or more fuel-burning appliances are connected to the same chimney flue, the appliances shall be located on the same storey.
3) Intent StatementThe connection referred to in Sentence (2) for a solid-fuel-burning appliance shall be made below connections for appliances burning other fuels.
4) Intent StatementThe 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.
9.21.2.3. Inclined Chimney Flues
1) Intent StatementChimney flues shall not be inclined more than 45° to the vertical.
9.21.2.4. Size of Chimney Flues
1) Intent StatementExcept 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).
2) Intent StatementWhere a chimney flue serves only one appliance, the flue area shall be at least equal to that of the flue pipe connected to it.
9.21.2.5. Fireplace Chimneys
1) Intent StatementThe 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
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) Intent StatementThe width of an oval chimney flue shall be not less than two-thirds its breadth.

9.21.3. Chimney Lining

9.21.3.1. Lining Materials
1) Intent StatementEvery masonry or concrete chimney shall have a lining of clay, concrete, firebrick or metal.
9.21.3.2. Joints in Chimney Liners
1) Intent StatementJoints 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.
2) Intent StatementJoints of clay, concrete or firebrick chimney liners shall be struck flush to provide a straight, smooth, aligned chimney flue.
9.21.3.3. Clay Liners
1) Intent StatementClay liners shall conform to CAN/CSA-A324-M, “Clay Flue Liners.”
2) Intent StatementLiners 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.
9.21.3.4. Firebrick Liners
1) Intent StatementFirebrick liners shall conform to ASTM C 27, “Classification of Fireclay and High-Alumina Refractory Brick.”
2) Intent StatementFirebrick liners shall be laid with high temperature cement mortar conforming to CAN/CGSB-10.3, “Air Setting Refractory Mortar.”
9.21.3.5. Concrete Liners
1) Intent StatementConcrete flue liners shall conform to Clause 4.2.6.4 of CAN/CSA-A405-M, “Design and Construction of Masonry Chimneys and Fireplaces.”
9.21.3.6. Metal Liners
1) Intent StatementMetal liners shall be constructed of not less than 0.3 mm thick stainless steel.
2) Intent StatementMetal liners referred to in Sentence (1) shall only be used in chimneys serving gas- or oil-burning appliances. (See Appendix A.)
9.21.3.7. Installation of Chimney Liners
1) Intent StatementChimney liners shall be installed when the surrounding masonry or concrete is placed.
9.21.3.8. Spaces between Liners and Surrounding Masonry
1) Intent StatementA space not less than 10 mm wide shall be left between a chimney liner and surrounding masonry.
2) Intent StatementThe space required in Sentence (1) shall not be filled with mortar.
9.21.3.9. Mortar for Chimney Liners
1) Intent StatementChimney liners used in chimneys for solid-fuel-burning appliances shall be laid in a full bed of
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) Intent StatementChimney 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.
9.21.3.10. Extension of Chimney Liners
1) Intent StatementChimney 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.

9.21.4. Masonry and Concrete Chimney Construction

9.21.4.1. Unit Masonry
1) Intent StatementUnit masonry shall conform to Section 9.20.
9.21.4.2. Concrete
1) Intent StatementConcrete shall conform to Section 9.3.
9.21.4.3. Footings
1) Intent StatementFootings for masonry chimneys and concrete chimneys shall conform to Section 9.15.
9.21.4.4. Height of Chimney Flues
1) Intent StatementA chimney  flue shall extend not less than
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) Intent StatementExcept as provided in Sentence (2), chimneys shall be braced in accordance with Subsection 4.3.2. to provide lateral stability under wind loads.
2) Intent StatementA chimney need not be laterally braced provided
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) Intent StatementThe top of a chimney shall have a waterproof cap of reinforced concrete, masonry or metal.
2) Intent StatementThe 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.
3) Intent StatementCast-in-place concrete caps shall be separated from the chimney liner by a bond break and be sealed at that location.
4) Intent StatementJointed precast concrete or masonry chimney caps shall have flashing installed beneath the cap extending from the liner to the drip edge.
9.21.4.7. Cleanout
1) Intent StatementA cleanout opening with a metal frame and a tight-fitting metal door shall be installed near the base of the chimney flue.
9.21.4.8. Wall Thickness
1) Intent StatementThe walls of a masonry chimney shall be built of solid units not less than 75 mm thick.
9.21.4.9. Separation of Flue Liners
1) Intent StatementFlue 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.
2) Intent StatementFlue liners referred to in Sentence (1) shall be installed to prevent significant lateral movement.
9.21.4.10. Flashing
1) Intent StatementJunctions with adjacent materials shall be adequately flashed to shed water.

9.21.5. Clearance from Combustible Construction

9.21.5.1. Clearance from Combustible Materials
1) Intent StatementThe clearance between masonry or concrete chimneys and combustible framing shall be not less than
a) 50 mm for interior chimneys, and
b) 12 mm for exterior chimneys.
(See Appendix A.)
2) Intent StatementA clearance of not less than 150 mm shall be provided between a cleanout opening and combustible material.
3) Intent StatementCombustible flooring and subflooring shall have not less than a 12 mm clearance from masonry or concrete chimneys.
9.21.5.2. Sealing of Spaces
1) Intent StatementAll spaces between masonry or concrete chimneys and combustible framing shall be sealed top or bottom with noncombustible material.
9.21.5.3. Support of Joists or Beams
1) Intent StatementJoists 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.