Fireplace Construction and Layout
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CHAPTER 40
Fireplace Construction
and Layout
I N T R O D U C T I O N
Thought was given to the type and location of the fireplace in
Chapter 18 when the floor plan was drawn. As the sections are
being drawn, consideration must be given to the construction
of the fireplace and chimney. The most common construction
materials for a fireplace and chimney are masonry and metal. The
metal, or zero-clearance, fireplace is manufactured and does not
require a section to explain its construction. A metal fireplace is
surrounded by wood walls that can be represented on the floor
or framing plans. Figure 40-1 shows a metal fireplace installed
in a wood-frame chase. The interior can be covered in masonry,
stone, tile or some other noncombustible material, as in Figure
40-2. Metal fireplaces are available that do not require a chimney.
Notice in Figure 40-1 that a side-venting metal chimney has been
provided. This vent functions more like a dryer vent than a
chimney, providing an outlet for exhaust gases. Figure 40-3
shows a gas-burning fireplace that is vented through the wall.
FIREPLACE ALTERNATIVES
Three common alternatives to a masonry fireplace
include direct-vent, top-vent, and vent-free fireplaces.
Direct-vent fireplaces vent out the back of the appli-
ance and through the house wall to outside air as FIGURE 401 Metal fireplace insert encased with standard
shown in Figure 40-3. Top-vent fireplaces can be used wood framing.
as a fireplace insert or as a freestanding unit as seen in
Figure 40-1. When used as an insert, the unit is installed
in an existing masonry fireplace, and it vents through
the fireplace’s existing chimney. When installed as a
fireplace, a metal chimney is provided, and both are
enclosed with a wood-frame chase.
A vent-free fireplace has no exhaust vent. A gas line
is connected to the unit and the flame burns inside
the fireplace without a vent. Not all states allow the
use of vent-free gas fireplaces because of conflicts with
building codes that require airtight, energy-efficient
construction. Although exterior air is required to be
provided for factory-built fireplaces, the IRC allows
the use of vent-free units if the room is mechanically
ventilated and controlled so that the indoor air pressure
is either positive or neutral. Many vent-free fireplaces FIGURE 402 Metal fireplace units can be covered in masonry,
are equipped with an oxygen-depletion sensor that stone, tile, or some other noncombustible material.
914
Chapter 40: Fireplace Construction and Layout 915
SPARK ARRESTER SCREEN CLAY FLUE LINER
2" MORTAR CAP
1 1/2" (40 mm) MIN. METAL FLASHING
GROUT BTWN. 4" CMU
& FLUE LINER CRICKET
4" (100 mm) CMU IF
LINED / 8" (200 mm)
IF UNLINED
VERT. STEEL REINFORCING STEEL ANCHOR STRAP
2" MIN HORIZ. STEEL
REINFORCING
MORTAR FILL
SMOKE CHAMBER
DAMPER
SMOKE SHELF
THROAT
FIREBRICK LINER
LINTEL
26"
ASH DUMP
8" 20" 18"
MIN MIN.
.
FIGURE 403 Exterior view of a self-venting gas fireplace; it CLEAN OUT
requires a vent similar to a dryer.
12"
terminates the gas supply to the fire if it senses a lack of
oxygen in the room.
When working with factory-built fireplaces, several 6" 4" (100 mm) MIN.
THICK HEARTH
items must be specified. The IRC requires the chimney
for direct- and top-vent fireplaces to conform to UL FIGURE 404 Parts of a masonry fireplace and chimney.
standard 127. Factory-built fireplaces producing gases
with a temperature above 1000°F (540°C) at the chim-
ney entrance must meet UL 959. Although a section occurs and will be explored shortly. The size of the
is not required, each of these chimney specifications fireplace opening is important for the appearance and
should be provided on the floor plan or interior eleva- operation of the fireplace. If the opening is too small,
tions, along with instructions to provide and install all the fireplace will not produce a sufficient amount of
materials per the manufacturer’s specifications. heat. If the opening is too large, the fire could make a
room too hot. Common design guidelines suggest that
the opening be approximately 1/30 of the room area
FIREPLACE TERMS
for small rooms, and 1/65 of the room area for large
Fireplace construction has its own vocabulary, which rooms. Table 40-1 shows suggested fireplace-opening
a drafter should know in order to draw a section. sizes relative to the room size. The ideal dimensions for
Although some of these terms apply to prefabricated a single-face fireplace have been determined to be 36"
fireplace units, they primarily relate to masonry fire- (900 mm) wide and 26" (650 mm) high. These dimen-
places. Figure 40-4 shows the major components of a sions may be varied slightly to meet the size of the brick
masonry fireplace and chimney. Terms are grouped by or to fit other special dimensions of the room.
components in the firebox and the chimney to aid in The fireplace opening is the front of the firebox
learning their location and function. where the combustion of the fuel occurs. The opening
to the firebox may be on one, two, or three sides of the
fireplace. The more openings that are provided, the
Terms Related to the Firebox
more decorative and less efficient the unit becomes.
The fireplace opening is the area between the side and Units can also be constructed so that the firebox is
top faces of the fireplace that serves as the front of the covered with a hood allowing it to be totally open.
firebox. The firebox is the area where the combustion Totally open fireplaces are typically used outside on
916 Architectural Drafting and Design
Suggested Width of Fireplace Openings Appropriate to Room Size
SIZE OF ROOM IF IN SHORT WALL IF IN LONG WALL
(FT) (MM) (IN.) (MM) (IN.) (MM)
10 ⫻ 14 (3048 ⫻ 4267) 24 (610) 24–32 (610–813)
12 ⫻ 16 (3658 ⫻ 4877) 28–36 (711–914) 32–36 (813–914)
12 ⫻ 20 (3658 ⫻ 6096) 32–36 (813–914) 36–40 (914–1016)
12 ⫻ 24 (3658 ⫻ 7315) 32–36 (813–914) 36–48 (914–1219)
14 ⫻ 28 (4267 ⫻ 8534) 32–40 (813–1016) 40–48 (1016–1219)
16 ⫻ 30 (4877 ⫻ 9144) 36–40 (914–1016) 48–60 (1219–1524)
20 ⫻ 36 (6096 ⫻ 10 973) 40–48 (1016–1219) 48–72 (1219–1829)
TABLE 401 The Size of the Fireplace Should Be Proportioned to the Size of the Room (This will give both a pleasing appearance and
a fireplace that will provide sufficient heat without overheating the room.)
a patio or as a divider between rooms. For a fireplace greater than 6 sq ft (0.557 m2), the hearth extension
with only one opening, the sides should be slanted must be increased to be 20" (500 mm) minimum with
slightly to radiate heat into the room. The rear wall 12" (300 mm) minimum side extensions. An ash dump
is inclined to provide an upward draft into the upper is usually located in the inner hearth of a masonry
part of the fireplace and chimney. The firebox is usually fireplace.
constructed of fire-resistant brick set in fire-resistant The ash dump is an opening in the inner hearth into
mortar. Figure 40-5A and Figure 40-5B show mini- which ashes can be dumped. The ash dump is covered
mum wall thickness for the firebox and other fireplace with a small metal plate, which can be removed to
components. provide access to the ash pit. The ash dump must be
The minimum depth of the firebox is required located so that the ash removal will not create a hazard
to be 20" (500 mm). The firebox depth should be to combustible materials. The ash pit is the space below
proportional to the size of the fireplace opening. the fireplace where the ashes can be stored.
Providing a proper depth ensures that smoke will not The outer hearth may be made of any noncombus-
discolor the front face (breast) of the fireplace. With tible material. The material is usually selected to blend
an opening of 36" × 26" (900 × 650 mm), a depth of 20" with other interior design features and may be brick,
(500 mm) should be provided for a single-face fire- tile, marble, or stone. The outer hearth protects the
place. Table 40-2 lists recommended fireplace opening- combustible floor around the fireplace.
to-depth proportions. Above the fireplace opening is a lintel. The lintel is
The hearth is the floor of the firebox and con- a reinforced masonry or steel angle that supports the
sists of an inner and outer hearth. The inner hearth masonry above the fireplace face. The minimum required
is the floor of the firebox. The hearth is made of bearing length for the lintel at each end of the fireplace is
fire-resistant brick and holds the burning fuel. The 4" (100 mm). The throat of a fireplace is the opening at
structural portion of the hearth must be made of 4" the top of the firebox that opens into the chimney. The
(100 mm) minimum reinforced masonry or concrete, throat must be at least 8" (203 mm) above the fireplace
but the portion that extends in front of the fireplace opening and must be a minimum of 4" (100 mm) in
can be a minimum of 2" (50 mm) thick. The hearth depth. The cross-sectional area of the passageway above
is required to extend 16" (400 mm) in front of the the firebox, including the throat, damper, and smoke
fireplace opening and 8" (200 mm) beyond each side chamber, can’t be less than the cross-sectional area
of the fireplace. If the size of the fireplace opening is of the flue. The throat should be closable when the
Chapter 40: Fireplace Construction and Layout 917
General Code Requirements
ITEM LETTER UNIFORM BUILDING CODE* 1997
Hearth Slab Thickness A 4”
Hearth Slab Width B 8” Fireplace opg. ⬍ 6 sq. ft.
(Each side of opening) 12” Fireplace opg. ⱖ 6 sq. ft.
Hearth Slab Length C 16” Fireplace opg. ⬍ 6 sq. ft.
(Front of opening) 20” Fireplace opg. ⱖ 6 sq. ft.
Hearth Slab Reinforcing D Reinforced to carry its own weight and all imposed loads.
Thickness of Wall or Firebox E 10” common brick or 8” where a fireback lining is used.
Jts. in fireback 1/4” max.
Distance from Top of Opening to Throat F 6”
Smoke Chamber Edge of Shelf G
Rear Wall—Thickness 6”
Front & Side Wall—Thickness 8”
Chimney H Four #4 full length bars for chimney up to 40” wide. Add two #4 bars
Vertical Reinforcing for each additional 40” or fraction of width or each additional flue.
Horizontal Reinforcing J 1/4” ties at 18” and two ties at each bend in vertical steel.
Bond Beams K No specified requirements.
Fireplace Lintel L Noncombustible material.
Walls with Flue Lining M Solid masonry units or hollow masonry units grouted solid with at
least 4” nominal thickness.
Walls with Unlined Flue N 8” solid masonry.
Distance between Adjacent Flues O 4” including flue liner.
Effective Flue Area P See Figure 40–6.
(Based on Area of Fireplace Opening) Verify with local code.
Clearances R 1” when outside of wall or 1/2” gypsum board.
Wood Frame 2” when entirely within structure.
Combustible Material 6” min. to fireplace opening.
Combustible material within 12” (305 mm) of the fireplace opening
can’t extend more than 1/8” for each inch (3/25 mm) distance from
the opening.
Above Roof 2’ at 10’
Anchorage S
Strap 3/16” ⫻ 1”
Number 2
Embedment into Chimney 12” hooked around outer bar w/6” ext.
Fasten to 4 joists
Bolts Two 1/2” dia.
Footing T
Thickness 12” min.
Width 6” each side of fireplace wall.
Outside Air Intake U Optional
Glass Screen Door Optional
FIGURE 405A General code requirements for fireplace and chimney construction. The letters in the second column will be helpful in
locating specific items in Figure 40-5B.
918 Architectural Drafting and Design
E
BRICK BLOCK
10'-0' MIN.
CLEARANCE L
MORTAR OR
MASONRY CAP R
2'-0"
MIN.
8" WIDTH OF
B
K BOND BEAM FIREPLACE
OPENING
10'-0' MIN.
EFFECTIVE FLASHING
P CLEARANCE
FLUE AREA
MORTAR CAP
HORIZONTAL R
MIN.
2'-0"
J
BOND BEAM
K
4" CMU
FLASHING
ANCHORAGE EFFECTIVE
S P
FLUE LINING FLUE AREA
6"
MIN.
HORIZONTAL
J
REINFORCING
BOND BEAM
K TIES
BOND BEAM
WALL THICKNESS K
M R
PARGE w/ MORTAR ANCHOR STRAP 1 1/2" MIN.
N R S
FLUE LINER GROUT BTWN. 4"
CMU & CLAY
VERTICAL 4" FLUE LINING
H
REINFORCING MIN.
21" MINIMUM
SMOKE
THERMAL
DISTANCE
8" . 8" G
IN CHAMBER
SMOKE CHAMBER M
G MIN.
F VERT. REINF.
H
20" LAP IF
F SPLICED TO
FTG. DOWELS
LINTEL
L
HEARTH
L
32"
EXTENSION
FIREBOX WALL
FIREBOX WALL 20" C E
E C THICKNESS
THICKNESS MIN.
HEARTH SLAB
HEARTH SLAB A
A THICKNESS
THICKNESS
NATURAL GRADE
BARS IN
CONCRETE
OPTIONAL FOOTING
FOOTING T DEPTH
CLEAN OUT HEARTH SLAB
D
REINFORCEMENT
OPTIONAL
ASH DUMP 4" (100mm) MIN. FOOTING WIDTH
T
T THICK HEARTH 6" AROUND FREE
STANDING FIREPLACE
BRICK FIREPLACE & CHIMNEY BRICK FIREPLACE / BLOCK CHIMNEY
FIGURE 405B Brick fireplace and chimney components. The circled letters refer to item references in Figure 40-5A.
fireplace is not in use. The flow of air through the fire-
place throat is controlled by a damper. The damper
Chimney Terms
must be made of ferrous metal that extends the full The smoke chamber acts as a funnel between the fire-
width of the throat to prevent heat from escaping up box and the chimney. The shape of the smoke chamber
the chimney when the fireplace is not in use. When should be symmetrical so that the chimney draft pulls
fuel is being burned in the firebox, the damper can be evenly and creates an even fire in the firebox. The smoke
opened from inside the room that contains the fireplace chamber should be centered under the flue in the
to allow smoke from the firebox into the smoke cham- chimney and directly above the firebox. The overall
ber of the chimney. size of the smoke chamber is regulated by the IRC.Chapter 40: Fireplace Construction and Layout 919
Width of Height of Depth of
Opening (W) Opening (H) Opening (D)
FIREPLACE
TYPE (IN.) (MM) (IN.) (MM) (IN.) (MM)
Single face 28 700 24 600 20 500
30 760 24 600 20 500
30 760 26 660 20 500
36 900 26 660 20 500
36 900 28 700 22 560
40 1000 28 700 22 560
48 1200 32 800 25 635
Two faces 34 865 27 685 23 585
adjacent ”L” 39 990 27 685 23 585
or corner type 46 1170 27 685 23 585
52 1320 30 760 27 635
Two faces* 32 800 21 530 30 760
opposite 35 890 21 530 30 760
look-through 42 1070 21 530 30 760
48 1200 21 530 34 865
Three face* 39 990 21 530 30 760
2 long, 1 short 46 1170 21 530 30 760
3-way opening 52 1320 21 530 34 865
Three face* 43 1090 27 685 23 585
1 long, 2 short 50 1270 27 685 23 585
3-way opening 56 1420 30 760 27 686
*Fireplaces open on more than front and one end are not recommended.
TABLE 402 Guide for Fireplace Opening-to-Depth Proportions
The inside height of the chamber can’t be greater than The chimney is the upper extension of the fireplace
the inside width of the fireplace opening. The walls of the and is built to carry off the smoke from the fire. The
smoke chamber must be made of solid masonry units, main components of the chimney are the flue, lining,
stone, concrete, or hollow masonry units that have been anchors, cap, and spark arrester. The wall thickness
filled with grout. The material is corbelled to form the of the chimney will be determined by the type of flue
tapered shape, but the IRC requires that the interior construction. Masonry chimneys are not allowed to
surface of the masonry units should not be exposed change in size or shape within 6" (150 mm) above or
to the smoke chamber. The walls of the smoke cham- below any combustible floor, ceiling, or roof compo-
ber can’t be greater than 30° when formed from cor- nent penetrated by the chimney. Figure 40-5A shows
belled masonry units, but can be inclined up to 45° the minimum wall thickness for chimneys.
if prefabricated linings are used. If the walls of the The flue is the opening inside the chimney that
chamber are made with a lining of 2" (50 mm) fire- allows smoke and combustion gases to pass from the
brick or of 5/8" (16 mm) vitrified clay, each of the four firebox away from the structure. A flue may be con-
chamber walls must have a minimum thickness of 6" structed of normal masonry products or may be covered
(150 mm), including the liner. If no lining is provided, with a flue liner. The size of the flue must be propor-
the four chamber walls must each be a minimum of 8" tional to the size of the firebox opening and the number
(200 mm) thick. A smoke shelf is located at the bottom of open faces of the fireplace. A flue that is too small will
of the smoke chamber behind the damper. The smoke not allow the fire to burn well and will cause smoke to
shelf prevents downdrafts from the chimney entering exit through the front of the firebox. A flue that is too
the firebox. large for the firebox will cause too great a draft through920 Architectural Drafting and Design
3000
2800
2600
2400
MIN. CROSS-SECTIONAL AREA (SQ. IN.) 224 269 2200
2000
187 214 1800
1600
140 168 1400
1200
110 124
1000
76 91 800
70 82 600
53 58
400
32 37
200
RECTANGULAR
OPENING AREA
13 14 15 16 17 18 19 20 21 22 23 24 25
SQUARE OR
FIREPLACE
(SQ. IN.)
ROUND
HEIGHT, MEASURED FROM FLOOR
FLUES
FLUES
OF COMBUSTION CHAMBER TO
TOP OF FLUE (FT.)
FOR SI: 1 foot = 304.8 mm, 1 square inch = 645.16 mm2.
FIGURE 406 Flue sizes for masonry chimneys based on the IRC. Courtesy 2009 International
Residential Code, Copyright © 2009, Washington, DC. International Code Council. Reproduced with
permission. All rights reserved. www.iccsafe.org.
the house as the fire draws its combustion air. Flue sizes The masonry cap is built so that openings allow for the
are generally required to equal either 1/8 or 1/10 of the prevailing wind to blow through the hood and create
fireplace opening. Figure 40-6 shows required flue sizes a draft in the flue. The metal hood can be rotated by
based on the IRC. Figure 40-7 shows recommended wind pressure to keep the opening of the hood down-
areas for residential fireplaces based on the size and wind and thus prevent rain or snow from entering the
number of openings. flue. A spark arrester is a screen placed at the top of
A chimney liner is usually built of fire clay or terra- the flue inside the hood to prevent combustibles from
cotta. The liner is built into the chimney to provide leaving the flue.
a smooth surface to the flue wall and to reduce the
width of the chimney wall. The smooth surface of the Chimney Reinforcement
liner will help reduce the buildup of soot, which could In areas subject to seismic damage, a minimum of
cause a chimney fire. The chimney cap is the sloping four vertical reinforcing bars 1/2" (13 mm) in diam-
surface on the top of the chimney. The slope pre- eter (#4) must be used in the chimney, extending
vents rain from collecting on the top of the chimney. from the foundation up to the top of the chimney.
The flue normally projects 2" to 3" (50 to 75 mm) These vertical bars are supported at 18" (450 mm)
above the cap so that water will not run down the intervals with a 1/4" (6 mm) horizontal rebar. Two
flue. The chimney hood is a covering that may be additional #4 bars are required for each additional
placed over the flue for protection from the elements. 40" (1000 mm) of width, or fraction thereof, or for
The hood can be made of either masonry or metal. each additional flue that is added to the chimney.Chapter 40: Fireplace Construction and Layout 921
AREA OF FIRE- FLUE SIZE
WIDTH OF HEIGHT OF DEPTH OF PLACE OPENING REQUIRED AT 1/10 FLUE SIZE
OPENING OPENING OPENING FOR FLUE AREA OF REQUIRED AT 1/8
TYPE OF W H D DETERMINATION FIREPLACE AREA OF
FIREPLACE IN. IN. IN. SQ IN. OPENING FIREPLACE OPENING
28 24 20 672 8 1/2 ⫻ 13 8 1/2 ⫻ 17
30 24 20 720 8 1/2 ⫻ 17 13” round
30 26 20 780 8 1/2 ⫻ 17 10 ⫻ 18
36 26 20 936 10 ⫻ 18 13 ⫻ 17
36 28 22 1008 10 ⫻ 18 10 ⫻ 21
40 28 22 1120 10 ⫻ 18 10 ⫻ 21
48 32 25 1536 13 ⫻ 21 10 ⫻ 21
60 32 25 1920 17 ⫻ 21 21 ⫻ 21
34 27 23 1107 10 ⫻ 18 10 ⫻ 21
39 27 23 1223 10 ⫻ 21 13 ⫻ 21
46 27 23 1388 10 ⫻ 21 13 ⫻ 21
52 30 27 1884 13 ⫻ 21 17 ⫻ 21
64 30 27 2085 17 ⫻ 21 21 ⫻ 21
32 21 30 1344 13 ⫻ 17 or 10 ⫻ 21 17 ⫻ 17 or 13 ⫻ 21
35 21 30 1470 17 ⫻ 17 or 13 ⫻ 21 17 ⫻ 21
42 21 30 1764 17 ⫻ 21 17 ⫻ 21
48 21 34 2016 17 ⫻ 21 21 ⫻ 21
39 21 30 1638 13 ⫻ 21 or 17 ⫻ 17 17 ⫻ 21
46 21 30 1932 17 ⫻ 21 21 ⫻ 21
52 21 34 2184 17 ⫻ 21 21 ⫻ 21
43 27 23 1782 13 ⫻ 21 or 17 ⫻ 17 17 ⫻ 21
50 27 23 1971 17 ⫻ 21 17 ⫻ 21
56 30 27 2490 21 ⫻ 21 21 ⫻ 21 or
68 30 27 2850 13 ⫻ 21 & 䊱 2—1 0 ⫻ 21 䊱
10 ⫻ 21 2—1 3 ⫻ 21 or
2—1 7 ⫻ 17 or 䊱
10 ⫻ 18 & 17 ⫻ 21
䊱 Rather than using two flue liners in chimney, the flue is often left unlined with 8˝ masonry walls. Unlined flues must have a minimum area of 1/8
fireplace opening.
FIGURE 407 Recommended flue areas for residential fireplaces.
Two #4 rebar are also installed when the vertical steel DRAWING THE FIREPLACE SECTION
is bent for a change in chimney width. In addition to
the reinforcement in the chimney, the chimney must The section for a masonry fireplace can be a valuable part
be attached to the structure in some seismic areas. of the working drawings. Although a fireplace drawing
This is done with steel anchors that connect the is required by most building departments when a home
fireplace to the framing members at each floor and has a masonry fireplace and chimney, a drafter may not
ceiling level that is more than 6' (1800 mm) above be required to draw a fireplace section. Because of the
the ground. Two 3/16" × 1" (5 × 25 mm) steel straps similarities of fireplace design, a fireplace drawing is
must be embedded 12" (300 mm) minimum into the often kept on file as a stock detail at many offices. When
chimney, and they must be hooked around the outer a house that has a fireplace is being drawn, the drafter
steel rebar and extend 6" (150 mm) beyond the needs only to get the stock detail from a file, make the
bend. The straps must attach to four floor or ceiling needed copies, and attach them to the prints of the plans.
joists with two 1/2" (13 mm) bolts. These straps can If the drafter is using AutoCAD, the stock drawing can
be omitted if the chimney is built completely within be inserted into the working drawings. A stock detail can
the exterior walls. be seen at the end of the chapter.922
GOING
GREEN
Goals of an Energy-Efficient Fireplace
INTRODUCTION expelled up the chimney after combustion. As the air is
Heating and air quality are major considerations in gaining expelled after combustion, new air must be drawn into
LEED credits. A standard fireplace will provide very little the fire. If the air for combustion is taken from the room
assistance in heating a home or in gaining LEED credits being heated, a draft will be created. To reduce drafts
in the categories of Indoor Environmental Quality or and maximize the heat produced by the fire, combustion
Energy Atmosphere. To greatly increase the efficiency of air must be taken from an outside source or from spaces
a masonry fireplace, add glass doors, ductwork that will in the residence that are ventilated with outside air such
circulate the heated air through the lower portion of the as non-mechanically-ventilated crawl or attic spaces. The
chimney, and mechanical blowers. Using a UL-approved restrictions by the IRC specify that the exterior air intake
cast-iron stove or heating unit will add to the efficiency can’t be located in a basement or garage, and the air
and may qualify for LEED credits. Materials listed in CSI intake can’t be placed at an elevation higher than the
Division 10.35 can be used to provide supplemental heat firebox. When the floor plan was completed, a note was
to a residence. The efficiency of the heating unit will also placed on the plan reading:
depend on the choice of fuel. Common fuels include
wood, gas, and pellets. Provide a Screened, Closable Vent Within 24"
Of the Firebox.
Choosing Fuels Providing the note on the floor plan will help ensure
Burning wood to produce heat creates significant pollution; that a draft is not created. As the fireplace section
emissions of particulates, carbon monoxide, VOCs, and is drawn, the vent for air intake should be indicated.
methane are significantly greater from wood stoves than The vent should be placed on an exterior wall or
from any other common heating fuel. If sustainable wood in the back of the fireplace in a position that is high
is locally available, using it as a fuel has no net impact on enough above the ground so that it will not be blocked
global warming. Burning wood from sustainable forest by snow. Combustion kits are available that can be
compensates for the carbon emissions caused from installed in the duct, to heat the outside air before it
combustion. If wood is burned in an efficient cast-iron stove enters the firebox. Another alternative to drawing air
or fireplace that minimizes pollution, it can be a good fuel from the outside is to draw combustion air from the
choice. Products such as pellets or natural gas have superior cold-air return ducts of the heating system. The HVAC
burning efficiencies and reduced particulate emissions in contractor can calculate the needed size and provide
comparison to even the best wood stoves. Multi-fuel stoves a duct that takes the necessary cool air from inside the
have the capacity to efficiently burn pellets or other solid home to supply the fireplace.
fuels such as wood, corn, or coal. However, combustion
in interior spaces, particularly in a tight house, can be an Using the Heated Air Efficiently
indoor air-quality concern due to leakage of flue gases and Once the fire has heated the air in the firebox, that air
particulates. New wood stoves are much more efficient than must be used efficiently to heat the structure. Chapter 12
old ones, but pellet stoves are less polluting than even the introduced passive solar heating and the use of a
best EPA-certified wood stoves. masonry mass to store heat. A masonry fireplace and
chimney will provide mass to absorb, store, and radiate
Providing Air Supply the heat back into the room long after the fire is out.
In addition to adding charm and elegance to a room, a When a fireplace is built on an outer wall, the mass of
fireplace also needs to be functional. No matter what the the fireplace is often outside the structure, to increase
material is, consideration must be given to the air that the usable floor space. With the chimney outside the
will be used by the fireplace. Three points to consider are structure, the interior face of the fireplace is the only
how air will be supplied to the fire, how to use the heated surface that radiates heat back into the room. The
air created by the fire, and how to minimize heated air amount of heat radiated into a room is increased as
escaping through the chimney. more of the fireplace and chimney mass is located inside
Introduced in Chapter 12 and Chapter 27, newer the structure. Placing the fireplace and chimney totally
construction methods can greatly reduce the amount of within a structure will allow all surfaces of the masonry
air that enters the structure. When a fireplace is added to to radiate heat into the structure.
a relatively airtight residence, the fireplace can actually Altering the shape of the firebox will also increase
cool a room if proper precautions are not taken. Air must the amount of air radiated back to the room. Table 40-1
be provided to the fireplace for combustion, and air is shows common sizes of fireplace openings. Increasing923
GOING
GREEN
Goals of an Energy-Efficient Fireplace (Continued)
the width and height of the opening and decreasing
the depth of the fireplace will increase the amount of DECREASED 20"
heat in the room. This altered firebox shape is based on DEPTH
12" MIN.
the Rumford design that was popular through the mid-
1800s. It has been reinvented and has become popular in
many areas, and is now permitted by the IRC. Increasing
the length of the sidewalls and decreasing the length
INCREASED
ANGLE
of the rear walls will also increase the heat returned to
the room. Figure 40-8 shows the difference between a
Rumford-type firebox and traditional designs. A third
method of increasing the heat returned to the room is a
mechanical blower.
Decreasing Chimney Heat Loss
The traditional means of reducing heat loss up the
chimney has been a damper. The damper is opened
while the fire is burning and closed when the fire is out.
INCREASED
HEIGHT
Because the damper is not airtight, warm air from the
32" TYP.
room will rise and be drawn up the chimney. As the air in
the chimney cools, it will start a reverse current, drawing
cold air into the heated room. Placing a chimney on
an outer wall will increase this tendency, because the
chimney will be cooler. In very cold climates, the reverse RUMFORD FIREBOX TYPICAL FIREBOX
convection current can be reduced by an additional
damper at the top of the chimney. FIGURE 408 Comparison of a Rumford-style firebox and
traditional construction. The Rumford style, popular through
the mid-1800s, has been reinvented to increase the amount
of heated air that is returned to the room containing the
fireplace.
If you are required to draw a fireplace section, a print STEP 3 Lay out the foundation for the fireplace. The
of the floor plans will be needed to help determine wall footing must be 6" (150 mm) wider on each side
locations and the size of the fireplace. As the drawing than the fireplace and 12" (300 mm) deep.
for the fireplace is started, use construction lines. See STEP 4 Lay out the hearth to be 16" (400 mm) in front
Figure 40-9 for Step 1 through Step 4. of the fireplace. The hearth will vary in thickness,
depending on the type of finishing material used. If
the fireplace is being drawn for a house with a wood
Layout of the Fireplace floor, the hearth will require a 4" (100 mm) mini-
mum concrete slab projecting from the fireplace base
STEP 1 Lay out the width of the fireplace: 20" (500 mm)
to support the finished hearth.
for the firebox and 8" (200 mm) for the rear wall.
See Figure 40-10 for Step 5 through Step 8.
STEP 2Lay out all walls, floors, and ceilings that are
near the fireplace. Be sure to maintain the required STEP 5 Lay out the firebox. Assume that a 36" × 26" × 20"
minimum distance from the masonry to the wood as (900 × 650 × 500 mm) firebox will be used. See
determined by the code in your area. Figure 40-11 for guidelines for laying out the firebox.924 Architectural Drafting and Design
STEP 8
STEP 2
STEP 7
STEP 2
STEP 1
STEP 6
(STEP 6 REQUIRES
NO DRAWING. SEE
FIGURE 40.12 TO
DETERMINE THE STEP 5
FLUE SIZE.)
STEP 4
STEP 2
STEP 3
FIGURE 409 Fireplace layout using construction lines. FIGURE 4010 Layout of the firebox and flue using construc-
tion lines.
STEP 6 Determine the size of flue required. A 36" × 26"
(900 × 650 mm) opening has an area of 936 sq in. 60˚ 4" MIN. W/
LINER 100 mm
By examining Figure 40-12 you can see that a flue
with an area of 91 sq in. is required. The flue walls
4"
can be constructed using either 8" (200 mm) of 100 mm
200 mm
masonry or 4" (100 mm) of masonry and a clay flue
liner. If a liner is used, a 13" (325 mm) round liner
8"
is the minimum size required.
STEP 7 Lay out the flue with a liner. Draw the inte- 4" FIREBRICK
4"
rior face of the liner. The thickness will be shown 100 mm
26" TYP.
650 mm
100 mm
later.
STEP 8 Determine the height of the chimney. The IRC 20" MIN. 4"
500 mm 100 mm
requires the chimney to project 2' (600 mm) mini-
mum above any construction within 10' (3000 mm)
of the chimney (see Figure 40-13).
FIGURE 4011 Minimum sizes required for firebox layout.Chapter 40: Fireplace Construction and Layout 925
48
46
21
1 :1
"x
FL
44
U E 69
21
17
"
SI
HEIGHT OF FIREPLACE OPENING (INCHES)
"x
42
(2
13
Z E Q. I
21
"x
S
"(
40
17
21
22
"x
1 0"
" (1
N.
3
38
)
SQ
1 0"
1
73
2
7"
x1
1/
.I
SQ
(
N.
x2
1
1
8" (
36
1:
71
)
. IN
1"
)
13 "
O
112
SQ
13
TI
.)
(1 3
RA
4
34
"x
.
3/
RO
SQ
IN
8
TH
81
1
17
SQ
.)
1:
UN
ID
. IN
32
/2"
"(
W
. IN
D(
13
.)
TO
x1
.
4S
)
91
30
T
H
7"
Q.
SQ
G
81
EI
(8 7
IN
28
(H
. IN
.)
( 69
/2 " . I N . )
2
S
1:
.)
Q.
SQ
x1
26
I N.
3"
)
24
24 28 32 38 40 44 48 52 56 60 64 68 72
WIDTH OF FIREPLACE OPENING (INCHES)
GRAPH TO DETERMINE THE PROPER FLUE SIZE FOR A SINGLE-FACE FIREPLACE, BY
MATCHING THE WIDTH AND HEIGHT OF THE FIREPLACE OPENING, THE MINIMUM
FLUE SIZE CAN BE DETERMINED. ONCE THE MINIMUM FLUE SIZE HAS BEEN
DETERMINED, THE CHIMNEY SIZE CAN BE DETERMINED.
Nominal Actual Outside Effective Max. Area of Minimum Outside
Dimension of Dimensions of Flue Fireplace Dimension of
Flue Lining Flue Lining Area Opening Chimney
8 1/2" Round 8 1/2" Round 39 sq. in. 390 sq. in. 17" x 17"
8 1/2" x 13" oval 8 1/2" x 12 3/4" 69 sq. in. 690 sq. in. 17" x 21"
8 1/2" x 17" oval 8 1/2" x 16 3/4" 87 sq. in. 870 sq. in. 17" x 25"
13" Round 12 3/4" Round 91 sq. in. 1092 sq. in. 21" x 21"
10" x 18" oval 10" x 17 3/4" 112 sq. in. 1120 sq. in. 19" x 26"
10" x 21" oval 10" x 21" 138 sq. in. 1380 sq. in. 19" x 30"
13" x 17" oval 12 3/4" x 16 3/4" 134 sq. in. 1340 sq. in. 21" x 25"
13" x 21" oval 12 3/4" x 21" 173 sq. in. 1730 sq. in. 21" x 30"
17" x 17" oval 16 3/4" x 16 3/4" 171 sq. in. 1710 sq. in. 25" x 25"
17" x 21" oval 16 3/4" x 21" 223 sq. in. 2230 sq. in. 25" x 30"
21" x 21" oval 21" x 21" 269 sq. in. 2690 sq. in. 30" x 30"
FIGURE 4012 Common flue and chimney sizes based on the area of the fire-
place opening.
10' - 0"
Drawing with Finished-Quality Lines
STEP 9 Use bold lines to outline all framing materials, as
shown in Figure 40-14.
MIN.
2'-0"
STEP 10 Use bold lines to outline the masonry, flue liner,
and hearth.
STEP 11 Use thin lines at a 45° angle to crosshatch the
masonry.
STEP 12 Crosshatch the firebrick with lines at a 45° angle
so that a grid is created (Figure 40-15).
STEP 13 Draw all reinforcing steel with bold lines.
Check local building codes to determine what steel
will be required.
FIGURE 4013 The chimney is required to extend 2' (600 mm)
above any part of the structure that is within 10’ (3000 mm). STEP 14 Draw the lintel with a very bold line.926 Architectural Drafting and Design
STEP 10
STEP 9
STEP 11
STEP 9
STEP 12
FIGURE 4014 Draw all framing members with finished-quality FIGURE 4015 Darken all masonry materials.
lines.
STEP 15Draw the damper with a very bold line SECTION—MASONRY
(Figure 40-16). FIREPLACE CHECKLIST
Dimension the drawing. Items that must be
STEP 16 Plot this section and any required details
dimensioned include the following: using an appropriate scale on size D material and place
A. Height above roof. with other sections.
Use stock details from Chapter 38 to complete the
B. Width of hearth. section showing.
C. Width and height of firebox.
D. Width and depth of footings.
Plot
E. Wood-to-masonry clearance.
❑ Assume a scale 3/8" = 1'−0" minimum unless your
STEP 17 Place notes on the drawing using Figure 40-17 as instructor provides other instructions.
a guide. Notes will vary, depending on the code that
you follow and the structural material that has been ❑ Text: Assume all text to be 1/8" high, neatly aligned
specified on the floor, framing, and foundation plans. in columns.Chapter 40: Fireplace Construction and Layout 927
2" MORTAR CAP
CHIMNEY TO EXTEND
2'-0" ABOVE HIGHEST (2) #4Ø BOND BM.
POINT OF BUILDING
WITHIN 10'-0" 26 GA. FLASH.
STD. TRUSSES @
24" O.C.
STEP 13 3/16" X 1" STRAP
OVER 4 TRUSSES
MIN. W/ (2) 1/2" DIA. (4) #4Ø/40" WIDTH
LAGS EA. END W/ (2) #4 EA. ADD.
40" / FLUE.
1" MIN. CLR.
# 4Ø @ 18" O.C. MAX.
(2) 3/16" X 1" STRAPS
EMBEDDED 12" MIN.
INTO CHIMNEY & CLAY FLUE LINER
STEP 13 HOOKED AROUND
OUTER BAR W/ 6"
MIN. BEND. FASTEN
TO 4 JST. MIN W/ (2)
1/2" M.B MIN.
SOLID BLK. FOR (2) #4 TIES @ EA.
ANCHORAGE FLOOR, CEIL, ROOF
4 X 12 HDR. & EA. BEND IN VERT.
REBAR.
STEP 15 #4 TIES @ 18" O.C.
21" MINIMUM
8
MI " PARGED SMOKE
8" MIN.
N.
SHELF
STEP 14
C. I. DAMPER
FIREBRICK LINER
4"X 3"X 3/16" LINTEL
26"
16" 20" 8" MIN.
STEP 13 MIN. MIN.
C. T. HEARTH
2"MIN.
CLR.
FIGURE 4016 Draw all reinforcing steel.
1'-0"
3"
4" MIN. THICK
❑ Titles: Assume to be 1/4" high text minimum. HEARTH
8" 6"
(4) #4 EA. WAY
❑ Leader length/Leader location: Center of top line on 3'-8"
left/center of bottom line on right. FIREPLACE SECTION
❑ Insert drawings into a drawing sheet with a com- 1/2" = 1' - 0"
pleted title block.
FIGURE 4017 Place the notes and dimensions.
❑ Freeze viewports.
Drawing ❑ Show required beams and girders for construction
❑ Show the required material to construct the fireplace of roof, walls, and floor systems.
and chimney including: ❑ Spark arresters or chimney caps.
❑ Coordination with floor plan representation. ❑ Flue lines and chimney materials.
❑ Wall construction surrounding the chimney. ❑ Chimney reinforcement.
❑ Floor/foundation support that matches the foun- ❑ Headers, required metal hangers, and required
dation plan. blocking.928 Architectural Drafting and Design
❑ Firebox/combustion chamber construction.
❑ Smoke shelf, damper, lintel, firebrick.
❑ Hearth including ash dump, and cleanout. STEP 1
STEP 2
Annotation
❑ Specify all materials including:
STEP 2
❑ Spark arresters or chimney caps. STEP 4
STEP 1
❑ Flue lines and chimney materials. STEP 3
❑ Chimney reinforcement.
❑ Headers, required metal hangers. FIGURE 4018 Fireplace elevation layout.
❑ Firebox/combustion chamber materials.
❑ Smoke shelf, damper, lintel, firebrick thickness.
❑ Hearth material, ash dump size, and cleanout size. Elevation Layout
STEP 1 Lay out the size of the wall that will contain the
Dimensions fireplace.
❑ Floor to ceiling heights. STEP 2 Lay out the width of the chimney.
❑ Firebox opening height. STEP 3 Lay out the height and width of the hearth if a
raised hearth is to be used.
❑ Firebox depth.
STEP 4 Lay out the fireplace opening.
❑ Hearth extension in front of firebox.
❑ Height of hearth above the finish floor.
❑ Thickness of hearth is cantilevered. Finished-Quality Lines
❑ Throat clearance. Usually the designer will provide the drafter with a
rough sketch similar to Figure 40-19 to describe the
❑ Chimney height above roof 10' / 2' minimum.
finishing materials on the face of the fireplace. By using
❑ 2" clearance of chimney/wood framing at roof/wall this sketch and the methods described in Chapter 24,
and wood floor assemblies. the fireplace elevation can be drawn (see Figure 40-20).
❑ Foundation size/depth and 6" minimum extension Once the finishing materials have been drawn, the eleva-
beyond chimney. tion can be lettered and dimensioned as in Figure 40-21.
Notes will need to be placed on the drawing to describe
all materials. Dimensions will be required to describe:
FIREPLACE ELEVATIONS
1. Room height.
The fireplace elevation is the drawing of the fire-
place as viewed from inside the home. Fireplace 2. Hearth height.
elevations typically show the size of the firebox and 3. Fireplace opening height and width.
the material that will be used to decorate the face of 4. Mantel height.
the fireplace. Fireplace elevations can be drawn by
using the following steps. See Figure 40-18 for Step 1
through Step 4.Chapter 40: Fireplace Construction and Layout 929
FIGURE 4019 The drafter can often use the designer’s preliminary sketch as a guide when drawing
the finishing materials for a fireplace elevation.
RECESS THIS AREA
8" 2'-0" 4" MIN. 3'-0" 1'-0"
MIRROR
BY OWNER
4 X 12 OAK
MANTEL
1'-0"
OPEN TO
DINING
ROOM
4'-6"
3'-6"
2'-2"
3'-0"
LINE OF HEARTH
FIGURE 4020 Drawing the elevation with finished line USED BRICK
JUMBO PAVERS ON EDGE
quality.
LIVING ROOM
1/2" 1'-0"
FIGURE 4021 Lettering and dimensions for a fireplace
elevation.930 Architectural Drafting and Design
CADD APPLICATIONS
Drawing Fireplace Sections and Elevations with CADD
INTRODUCTION be used to organize materials. Once all objects have been
By following the steps that were provided for drawing assigned to the desired layers, dimensions and annotation
using manual methods, a fireplace section can be drawn can be assigned using the guidelines in Step 16 and Step 17.
with AutoCAD. Start by placing the lines required in Step 1 In many cases the architectural firm draws a number of
through Step 8 on the DETL OUTL layer. Once the major standard fireplace sections and details similar to Figure 40-22.
components have been outlined, the PROPERTIES command These typical sections are then saved in the CADD symbols
can be used to assign the desired line weight and color, library and called up when necessary to insert on a drawing.
and to place objects on the desired layer. Layers such as The standard sections may be completely dimensioned and
DETL MBND (material beyond cutting plane), DETL MCUT noted, or the dimensions and specific notes may be added
(material cut by the cutting plane), and DETL PATT can after the section is brought into the drawing.
FIREPLACE ELEVATIONS
CLAY FLUE LINER
Drawing fireplace elevations with AutoCAD is easy because
2" MORTAR CAP a fireplace elevation is normally either a fireplace box and a
* CHIMNEY TO EXTEND
2'-0" ABOVE HIGHEST
POINT OF BUILDING
surrounding mantel, or a fireplace box and a masonry wall.
WITHIN 10'-0"
METAL FLASHING
In either case the job is simple. If you are drawing fireplace
elevations with a surrounding mantel, draw a few standard
CRICKET
applications and add one of them to the drawing at any
SEE PLAN FOR time. Figure 40-23 shows a standard mantel in a fireplace
SIZE & SPACING
elevation. With most CADD programs, these symbols are
REINFORCING
(SEE NOTE BELOW) TYPICAL ANCHORAGE. dragged onto the drawing, and the computer gives you
SEE ATTACHED NOTE.
a chance to scale the display up or down. This provides
SEE PLAN FOR HEADER maximum flexibility for inserting the drawing. Once the
MANTEL - VERIFY STYLE
& FINISH w/ OWNER standard mantel has been added to the drawing, it can
be increased or decreased in size with commands such
as SCALE, TRIM, or STRETCH. If the fireplace elevation is a
masonry wall, all you do is define the area with lines and
PARGED SMOKE SHELF
4"X3"X 1/4" add elevation symbols such as stone or brick. ■
STEEL LINTEL
26"
CAST IRON DAMPER
8" 16"
MIN. TILE OR BRICK
FIREBRICK LINER HEARTH (VERIFY)
2" WIDE OAK
TRIM W/ DEC
CORNER SQUARES
4" PRECAST HEARTH OAK CROWN MOLDING
W/ #3 BARS @ 9" O.C.
12"
EA. WAY.
VINYL S.H.
6" 8" WINDOWS
'-0""
3'-0
'-0
3'-8" MIRROR W/
3
OAK TRIM
REINFORCING:
9'-0"
( SEE 2003 I.R.C. R1003.1)
-VERTICAL:
A MINIMUM OF (4) #4 FULL LENGTH BARS FOR
5'-0"
CHIMNEYS UP TO 40". (2) ADDITIONAL BARS FOR
EA. ADDITIONAL 40" ( OR FRACTION) OF WIDTH.
-HORIZONTAL:
FLUSH TILE CERAMIC TILE
1/4" TIES @ 18" o.c. w/ (2) TIES @ EA. BEND IN VERT. BARS. HEARTH TRIM
ANCHORAGE:
8" HIGH 2'-8" CAMBRIDGE DVL DIRECT
(2) 3/16" X 1" STEEL STRAP EMBEDDED INTO CHIMNEY 12" MIN. VENT FIREPLACE INSERT
BUILT-UP
HOOK AROUND OUTER VERT. BARS W/ 6" HOOK. FASTEN TO OAK BASE 5'-4" BY AVALON. INSTALL VENTING
FRAMING w/ (2) 1/2"¯ M.B. @ EA. STRAP. MOLDING PER MANUF. INSTRUCTIONS
FIREPLACE SECTION LIVING - EAST WALL
1/2" = 1' - 0" 1/2" 1'-0"
FIGURE 4022 A CADD fireplace section can be created as a FIGURE 4023 CADD representation of a fireplace with a
stock detail. masonry front.Chapter 40: Fireplace Construction and Layout 931
ADDITIONAL RESOURCES See CD for more information
The following Web sites can be used as a resource to help www.rumford.com Buckley Rumford Company
you keep current with changes in fireplace materials. (fireplaces)
These Web site links are also provided on the Student www.centralfireplace.com Central Fireplace
CD where you can select a link and go automatically to (gas fireplace)
the specified Web site. www.comfortglow.com Comfort Glow
Company, Product, www.hearthstonestoves.com HearthStone
Address or Service www.heatilator.com Heatilator
www.arcat.com ARCAT, Inc. (building prod- www.jotul.com Jøtul
uct information) www.majesticproducts.com Majestic
www.avalonfirestyle.com Avalon www.maconline.org Masonry Advisory Council
www.gobrick.com Brick Industry Association www.vermontcastings.com Vermont Castings
See CD
for more
Fireplace Construction and Layout Test information
QUESTIONS
DIRECTIONS: Answer the questions with short, complete state- Question 40–4 What is the required flue area for a
ments or drawings as needed on an 8 1/2" × 11" sheet of note- fireplace opening of 44" × 26" (1118 × 660 mm)?
book paper, as follows:
Question 40–5 What flues could be used for a fireplace
1. Letter your name, Chapter 40, and the date at the top of the opening of 1340 sq in. (864 514 mm2)?
sheet.
Question 40–6 How is masonry shown in cross section?
2. Letter the question number and provide the answer.
You do not need to write out the question. Answers may Question 40–7 Why is a fireplace elevation drawn?
be prepared on a word processor if course guidelines Question 40–8 Why is fireplace information often
allow it. placed in stock details?
Question 40–1 What purpose does a damper serve? Question 40–9 Where should chimney anchors be
placed?
Question 40–2 What parts does the throat connect?
Question 40–10 How far should the hearth extend
Question 40–3 What is the most common size for a
in front of the fireplace with an opening of 7 sq ft
fireplace opening?
(0.65 m2)?This page intentionally left blank
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