Firth Chimneys and Open Fireplaces PDF 3.6 MB

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FIRTH CHIMNEYS AND
OPEN FIREPLACES
January 2014
Precast open fireplaces continue to enjoy popularity with many
architects and builders, because of their aesthetic appeal and ease
of construction.
HOW IT WORKS
Room air is drawn into the fire chamber and through
the fuel bed, thereby supplying oxygen for the burning
process. Combustion gases and smoke rise from the
burning fuel to the throat and then through the flue to
the outer air. A correct balance between the sizes of
fire chamber, throat, flue cross sectional area and flue
length are essential to a continuous upwards discharge
draft of combustion gases and smoke. Satisfactory
dispersal of combustion gases and smoke could be
impeded by a flue being too big or too small in relation
to the size of the fire chamber.
Flue
Lintel
Mantle
Surround
Gathering
Smoke Shell
Throat
Fire back
Front
Hearth
Fire chamber
Grate
Tip Plate & Frame
Ash-dump
Hob
Foundation
The foundation should be excavated into naturally
solid ground (never less than 300mm deep) and be
of a sufficient area to ensure stability. The foundation
pad should be of reinforced concrete never less than
150mm thick.
Flue
The height of the chimney shaft above the roof line
should be greater than 600mm and less than 2400mm
above the highest part of the roof intersect. The top of
the chimney has to be more than 1500mm from the
nearest point of the roof measured horizontally.
Height
The maximum height for a sectional pumice chimney
is 9140mm, measured from the ground to the highest
point of the chimney cap. A minimum flue height of
4.6m is recommended for optimum performance.
Supports
Our sectional pumice chimneys should be secured to
the building at the ceiling, the roof line and at each
floor level with galvanised metal straps, at no less
than intervals of 2.4 metres. Suitable provision will
need to be included in the design of individual houses
to ensure that they possess adequate strength to resist
the horizontal wind and seismic loads which will be
transferred into the house frames from the chimney.
Mortar Joints
To join the pumice sections together, a full bed of
premixed mortar should be used.
Back
Hearth
\
Reinforcing
Base Slab
The chimney should have continuous vertical reinforcing
consisting of four 12mm deformed steel rods. The
reinforcing extends the full length of the chimney above
the gathering. All reinforcing should be grouted with
a high strength low shrinkage pourable cementicious
grout.
The base on all chimneys for an outdoor setting must
have a base larger than the chimney. This is to prevent
the chimney from falling over. An engineer should be
consulted to provide the correct dimensions for this
base.
Fire back
Fire bricks should be laid on the flat using a refractory
mortar, the sides of the fire chamber should be vertical,
but in plan view should be angled so as to reduce the
back width of the chamber, this back width should be
the same as that of the chosen grate.
The fire back should rise vertically for the first
150mm and then slope forward in a straight line
towards the throat.
Chimney Selection
The chimneys approved for an outdoor setting are;
•
•
•
•
Super Heat Master chimney
Standard Log Burner chimney
Super Log Burner chimney
Super Room Warmer chimney
FOR ALL NON STANDARD APPLICATIONS AN
ENGINEER SHOULD BE CONSULTED.
Timber
Framing
Cement
Compo.
The fire back must not be laid with a cruve as it rises,
because this could cause smoke to be curled forward
of the lintel and into the room. There should be a space
between the structural chimney and the fire back, this
space being filled with fine dry pumice and capped with
a smoke shelf which shall be dished.
Air Tight
Seal
TW
Throat
TH
H
Outdoor Chimney
For the outdoor chimney to draw properly, a minimum
height of 3.0m is recommended. For finishing we recommend plastering outdoor chimneys only.
Bracing Requirements
The maximum a chimney can be built free standing
without bracing is 2.4 metres. Because of the reinforcing
detail both the Log Burner chimneys require a wing
wall built behind the chimney for bracing purposes. The
Log Burner chimneys require bracing for the bases, sill
block rectangle, sill block gathering and in the case of
the Standard Log Burner the extension gathering as
well. Above this wing wall, 2.4 metres of freestanding
flue blocks including the cap can be installed.
ricks
Fireb
As
Narrow
As Possible
lope
ght S
Strai Curved)
(Not
The throat should be the full width of the fire chamber
and relatively narrow e.g. between 90mm and 100mm.
The fireback should rise at least 75mm higher than the
lintel.
D
Fine Shingle
Filling
For optimum performance a flue height of 4.6m
is recommended.
Wind conditions can influence the air flow into the
chimney and result in instances of smoke exiting
below the lintel.
Inside
260 x 150
230
Inside
335 x 230
150
390
490
410
510
Standard Flue Block
395
Extension Gathering
400
1090
Deflector
250
1090
570
Standard Heat Master Chimney
Base Section
Rectangle Gathering
Extension Gathering
Standard Flue Blocks
Standard Flue Cap
Base Section
Standard Flue Cap
Firebricks (80)
Steel Rod D12 (10 metres)
Refractite Cement (16kg)
710
890
1090
570
Note: Steel is not supplied.
Super Flue Cap
Inside
260 x 150
1090
70
410
Inside
350 x 250
Super Flue Block
1090
150
410
Open Gathering
1090
300
405
Deflector
250
1090
570
Base Section
710
Super Heat Master Chimney
Base Section
Rectangle Gathering
Open Gathering
Super Flue Block
890
Super Flue Cap
Firebricks (80)
Steel Rod D12 (10 metres)
Refractite Cement (16kg)
570
Note: Steel is not supplied.
210
Reinforcement Details
65
300
Hole Size 50mm dia.
50
50
300
400
300
1090
Inside
260 x 150
230
Inside
335 x 230
150
Standard Flue Cap
390
490
410
510
Standard Flue Block
380
Extension Gathering
400
1090
Sill Block Gathering
300
1600
405
Sill Block Rectangle
300
Standard Log Burner Chimney
Base Section Lower
Base Section Upper
Sill Block Rectangle
Sill Block Gathering
Extension Gathering
1600
580
Standard Flue Block
Standard Flue Cap
Firebricks (120)
Steel Rod D12 (10 metres)
Refractite Cement (24kg)
Base Section Upper
1410 600
1
355
590
Base Section Lower
1410 600
1
355
Note: Steel is not supplied.
590
70
410
150
410
300
300
Super Log Burner Chimney
Base Section Lower
Base Section Upper
Sill Block Rectangle
Sill Block Gathering
410
580
Super Flue Block
Super Flue Cap
Firebricks (120)
Steel Rod D12 (10 metres)
Refractite Cement (24kg)
1100
1600
Super Flue Block
Still Block Gathering
Still Block Rectangle
1600
1410 600
1
360
590
Note: Steel is not supplied.
60
60
460 crs
Hole Size 50mm dia.
60
Base Section Lower
1410 600
1
590
Reinforcement Details
1470 crs
1090
Super Flue Cap
Base Section Upper
360
60
1090
Inside
260 x 140
230
Inside
335 x 230
150
390
490
410
510
Standard Flue Block
430
Extension Gathering
1090
560
Deflector
250
1090
570
Standard Fireglow Chimney
Base Section
Deflector
Extension Gathering
Standard Flue Block
Standard Flue Cap
Base Section
Standard Flue Cap
Firebricks (80)
Steel Rod D12 (10 metres)
Refractite Cement (16kg)
710
890
570
1090
Note: Steel is not supplied.
Inside
260 x 150
70
Inside
350 x 250
150
1090
410
Super Flue Cap
Super Flue Block
1090
410
Open Gathering
300
1090
405
Deflector
250
1090
570
Base Section
710
Super Fireglow Chimney
Base Section
Deflector
Extension Gathering
Super Flue Block
Super Flue Cap
Firebricks (80)
Steel Rod D12 (10 metres)
Refractite Cement (16kg)
570
Note: Steel is not supplied.
210
Reinforcement Details
65
300
Hole Size 50mm dia.
50
50
300
400
300
890
1090
Inside
240 x 140
230
Inside
335 x 230
150
390
490
410
510
Standard Flue Cap
Standard Flue Block
430
Extension Gathering
1095
600
Gathering Slab
76
1244
600
Deflector
485
Standard Room Warmer Chimney
Base Section
Deflector
Gathering Slab
Extension Gathering
Standard Flue Blocks
Standard Flue Cap
Firebricks (80)
Steel Rod D12 (10 metres)
Refractive Cement (16kg)
600
1040
1244
Base Section
480
1040
600
1244
Note: Steel is not supplied.
Super Flue Cap
Inside
260 x 150
75
Inside
350 x 250
150
1090
410
Super Flue Block
1090
410
Open Gathering
300
410
Gathering Slab
75
1244
600
Deflector
485
600
Super Room Warmer Chimney
Base Section
Deflector
Gathering Slab
Extension Gathering
Super Flue Blocks
Super Flue Cap
Firebricks (80)
Steel Rod D12 (10 metres)
Refractive Cement (16kg)
Base Section
480
50
50
50
Hole Size 50mm dia.
120
120
300
400
300
1040
600
Note: Steel is not supplied.
Reinforcement Details
1040 4
124
1244
TECHNICAL SPECIFICATION - CHIMNEY FOUNDATION
Figure 1
lap
300mm
75mm hearth slab
D10 at 255mm ctrs each way
500mm
max
Timber floor (double joists
each side of hearth slab)
Floor line for
internal chimney
Foundation for base
lap
300mm
D12 starters at 400mm
max ctrs to match
vertical rods in chimney
300mm
lap
D12 at 400mm ctrs (300mm legs)
R6 U bars at 200mm ctrs in walls
150mm
min
300mm
min
200mm
Chimney foundation slab.
D12 at 300mm ctrs each way
or 661 mesh top and bottom
300mm leg
(A) Suspended Floor
Floor line for
internal chimney
lap
300mm
D12 starters at 400mm
max ctrs to match
vertical rods in chimney
400mm lap
Ground Floor Slab
150mm
Chimney foundation slab.
D12 at 300mm ctrs each way
or 661 mesh top and bottom
(B) Slab On Ground
D12 at 400mm ctrs max (300mm leg)
Lap 400mm with slab reinforcement
TECHNICAL SPECIFICATION - FLOOR AND ROOF BRACKETS
Figure 2
Chimney Stack
Ceiling Joist
Flashing
min 400mm
50mm x 4mm Galv. steel
strap. Three M12 bolts at
75mm min ctrs
Packer each side
See NZBC acceptable solution
B1/AS3 Paragraph 1.7.2
Floor and Roof Brackets
Note:
Although drawn for roof restraint of a chimney on an exterior wall, the bracket details also apply to
an interior chimney and floor restraint of chimneys.
TECHNICAL SPECIFICATION - CHIMNEY RESTRAINT
Figure 3
D12 grouted into
50mm Ø duct
Flue
90mm
Fixing Tie
See Note 1
Fixing Bracket
See Note 2
Packer. See
NZBC B1/AS3
Paragraph 1.7.2
Fix Bracket to stud
with 12mm Ø
coach screw
50mm
Double Stud
Option A
Notes:
1. Ties shall comprise 4mm galvanised hairpins located in
the mortar joints between units at no more than:
480mm maximum centres for stacks up to 600mm wide
320mm maximum centres for stacks over 600mm wide
Option B
Notes:
1. Brackets shall be made from 5mm thick M.S. angle with a
50mm hole drilled to suit the reinforcing duct. Locate brackets
in the mortar joints between units at no more than:
480mm maximum centres for stacks up to 600mm wide
320mm maximum centres for stacks over 600mm wide
TECHNICAL SPECIFICATION - STEEL REINFORCING DETAILS
Figure 4
Two outside stack
rods pass
continuously from
foundation to base
to gather to stack
Base rods to be
bonded 200mm min
into gather with a high
strength grout
A
A
Two inside stack
rods to be fixed a
minimum of
200mm into gather
with a high
strength grout
Plan
50mm dia
ducts for
reinforcing
rods
Chimney stack units
D12 grouted in
50mm diameter duct
50mm dia duct for
reinforcing in gather
D12 in high strength
grout over length of
200mm min
gather
D12 grouted in
50mm diameter duct
Chimney base
Section A-A
Chimney Foundation
and starters as in Fig. 1
TECHNICAL SPECIFICATION - BRICK VENEERS
Figure 5
A
fix to ceiling
joist with
3 x M12 galv.
bolts @
75mm min
centres
A
80 x 60 x 5mm M.S. angle
or 65 x 10mm M.S. flat
Grouting
between
chimney & brick
veneer shall be
17.5 mPa
Section A-A
Packer each side. See
NZBC acceptable solution
B1/AS3 Paragraph 1.7.2
50mm grouting cavity
Bricks shall
be fixed to
precast
chimney with
brickweld
between the
joints.
Firebricks
D12 at 400mm
max ctrs
(300mm min laps)
See Note
Max height 9m
50mm x 4mm
U strap at
roof level
See Note
above roof level fixing
2.4m max cantilever
Secured to wall (internal
or external) at no less than
intervals of 2.4 metres.
Precast Pumice Units
Brick Veneer
B
B
Section B-B
Vertical Section
Note:
Figure 5 has been drawn for the chimney being
exterior to the building
The dotted lines indicate the ceiling joists and floor for
an internal chimney.
SUSTAINABILITY: THE FIRTH CONCRETE & CONCRETE MASONRY SUSTAINABILITY LIFECYCLE
4 Environmentally compliant manufacturing plants
n
4 Surplus water and some aggregates recycled
n
4 Low transport impacts
n
4 Leftover concrete returned from construction sites
n
4 Passive solar heated thermal mass makes completed buildings
n
more energy-efficient
4
n
4
n
4
n
4
n
4
n
4
n
Most wash water returned from construction sites
For more on Firth’s
Highly durable, low maintenance buildings and no rot
contribution to building
High degree of noise control
a sustainable tomorrow
Inherent fire resistance
today, visit www.firth.co.nz
Overall longer effective building life
or call us on 0800 800 576
Demolished concrete can be recycled as hard fill or aggregate
for our free brochure.
© Copyright Firth 2010
Jan 2014 Chalis FIR21774
0800 800 576
www.firth.co.nz