B's Flashcards 1-500
The most significant characteristic of a building is not its architectural style but how it ___
Behaves under fire conditions
In the field of fire protection, how are buildings classified?
According to the manner in which they behave under fire conditions
All building codes classify buildings by ___
Construction type
What are the two attributes that building classifications are based on?
materials used in construction and the fire resistance ratings required for the structural components
In addition to classifying building by construction type, building codes classify buildings by their ___
Occupancy
What is fire resistance a function of? What are material properties related to fire resistance? (5 properties)
The properties of all materials used, including combustibility, thermal conductivity, chemical composition, density, and dimensions.
Fire resistance is __
The ability of a structural assembly to maintain its load bearing capacity and structural integrity under fire conditions
In the case of walls, partitions, and ceilings fire resistivity also means ___
The ability to act as a barrier to fire
How are fire resistance ratings expressed?
In hours and fractions of hours
A building code will typically require that columns supporting the floors in a fire-resistive building have a fire resistance rating of ___
3 hours
The walls enclosing an exit stairwell, which may or may not be load bearing, typically must have a fire resistive rating of ___ to protect the stairwell
1-2 hours
What are the three methods to determine fire resistance?
- Laboratory testing
- the development of mathematical models based on data collected during nonstandard testing 3. the use of statistical data to determine probability of fire resistance based on standard test results.
What is the most commonly used method of determining fire resistance?
Laboratory testing
When and where were the earliest known building material tests conducted?
1884-86 in Germany
When and where were the earliest fire tests in the US conducted?
Denver 1890 and New York 1896
NFPA 251
Standard Method of tests of fire endurance of building construction materials. Also designated as ASTM E-119
In the standard fire test, the furnace temperature is regulated to conform to a ___
uniform time-temperature curve
For the standard time-temperature curve, a temperature of ___ is reached in 5 minutes and ___ at 30 minutes. At one hour the temperature is ___.
1000; 1550; 1700 all in degree F; 1850 at 2 hours, 2000 at 4 hours, 2300 at 8 hours
Fire resistance tests are classified as either ___ or ___.
Load bearing or non-load bearing
Fire resistance ratings for floor and ceiling assemblies are developed for both __ and __ assemblies.
Restrained and unrestrained because the end restraints affect the extent to which an assembly may expand or rotate
When a structural specimen is tested, the test is continued until ___ or ___
The specimen fails or the specified fire endurance for which the specimen being tested is reached
Normally, assemblies are not tested beyond ___ because this is the maximum time required by the building codes.
Four hours
What are the primary points of failure for fire resistance testing? (4 things)
- Failure to support an applied load
- Temperature increase on the unexposed side of wall, floor, and roof assemblies of 250 degree F above the ambient temperature
- Passage of heat of flame through the assembly sufficient to ignite cotton waste
- Excess temperature on steel members
The failure point temperature of steel will depend on __
the application of the component
Where is UL headquarters located?
Northbrook, Illinois
What are the standard intervals for fire resistance ratings?
15 min, 30 min, 45 min, 1 hour, 1.5 hour, 2 ,3, 4 hour
What are the approx. plan dimensions of the UL test furnace for beams, floor, and roof assemblies?
14 x 17 feet
The standard test fire assumes an ___ and ___ to produce increasing temperatures.
Endless fuel supply and adequate ventilation
ASTM Standard 1529
Standard test methods for determining effects of Large hydrocarbon pool fires on structural members and assemblies
The ___ test is the only method currently universally accepted by building codes.
E-119 (NFPA 251)
Joint systems for floor to wall and wall to wall connections are tested in accordance with ___
UL standard 2079 “Standard for Fire Tests of Joint Systems”
Underwriters Laboratories annually publishes a ___ , which lists assemblies that have been tested and their fire resistance ratings
Fire resistance directory
Inspectors ___ allow deviations for the listings in the field.
Should not
What is the standard jointly created by ASCE and SFPE for the calculation of fire resistance for structural elements?
ASCE/SFPE 29
ASCE/SFPE 29 standard is limited to use with what materials? (5 things)
Structural steel, plain and reinforced concrete, timber and wood, concrete masonry, and clay masonry
What is the most commonly used structural steel designated?
A7 or A36, used for ASCE/SFPE 29 models
What is a designation for high strength steel?
A242
Fundamentally, a noncombustible material is one that ___
In the form in which used and under the conditions anticipated, will not ignite, burn, support combustion, or release flammable vapors, when subjected to fire or heat
What is the most commonly used test for determining combustibility? (Standard)
ASTM E-136 “Standard test method for behavior of materials in a vertical tube furnace at 750 degrees C”
What can be considered a masonry product? (5 things)
Bricks, blocks, stones, and unreinforced and reinforced concrete products
NFPA 220
Standard on types of building construction
In NFPA 220 each classification is designated by a ___ number code.
Three digit
Explain the three digit number code
1st digit fire rating in hours of exterior bearing walls
2nd digit fire rating of structural frames or columns and girders that support loads of more than one floor
3rd digit fire rating of floor
Building codes use the types of construction and building occupancy, in connection with __ and __ to establish limits on the heights and areas of buildings.
Sprinkler systems and separations
What is the 3 digit rating for type 1 construction?
4-4-3 or 3-3-2 or 4-4-2….they would have a hard time with this question
Generally in type 1 construction, bearing walls, columns, and beams are required to have a fire resistance of ___ hours.
2-4 hours
Floor construction for type 1 construction is required to have fire resistance of ___
2-3 hours
Roof deck fire resistance for type 1 construction
1-2 hours
Some building codes contain a provision to omit the fire resistive rating for a roof construction for some occupancies when the roof is located more than ___ feet above the floor.
20 feet
Are floor panels and roof panels considered part of the structural frame?
NO
The structural frame shall be considered to be the ___ having direct connections to the columns and bracing members designed to carry gravity loads. (4 things)
Girders, beams, trusses, and spandrels
For type 1 construction, a code may allow the use of fire retardant treated wood in ___
Roofs or interior partitions
In type 1 construction, combustible materials typically are permitted for such uses as the following: (9 things)
Roof coverings, interior floor finishes, interior wall finishes and trims, doors and door frames, window sashes and frames, platforms, nailing and furring strips, light-transmitting plastics, and foam plastics subject to restrictions
What are the two most common ways of constructing Type 1 buildings?
Using reinforced concrete or a protected steel frame
Unprotected steel has ___
No fire resistance
What is the structural fire resistance requirement for II-A construction?
One hour; type II-B is unprotected with no rating
An unprotected, noncombustible building ___ to provide structural stability under fire conditions.
Cannot be expected
The point at which unprotected members in type 2 construction fail depends on the following factors: (3 things)
- Ceiling height of the building,
- Size of the unprotected steel members,
- Intensity and duration of the exposing fire
For type 3 construction, interior structural members including walls, columns, beams, floors, and roofs are permitted to be __
Partially or wholly combustible
Type IIIA construction is required to have a __ fire resistive rating for interior members.
One hour; type III-B has no rating for interior members
Exterior bearing walls for type 3 construction should have a rating of ___
2 hours
The minimum dimensions for floor joist construction in Type 4 would be __
nominal 6 x 10
In type 3 construction it would not be uncommon to use __ joists for floor construction
nominal 2 x 10
Are concealed spaces permitted between structural members in Type 4 construction?
NO
Type 4 construction was used extensively in ___ in the __ and __ centuries.
Factories, mills, and warehouses; 19th and early 20th centuries
Today, heavy timber wood frame construction is encountered primarily where it is desired for ___
Appearance
If the heavy wood members have not been exposed to prolonged fire, it is possible to ___
Sandblast away the charring and continue their use after a fire
Many type 5 structures are required to have a ___ rating for the structural members.
1 hour; this is typically accomplished with plaster or gypsum
When was light frame construction introduced to the united states?
in the 1830s
Where might a mixed construction situation be found?
Where a different type of structure is built into an existing one
In some jurisdictions, it is permissible to have type 5 construction over type 1 up to a height of ___
70 feet
The fire load is the ___
Product of the weight of the combustibles multiplied by their heat of combustion
Ordinary combustibles such as wood, paper, and similar materials have heats of combustion between ___ and ___ BTU per pound.
7000-8000 btu per pound
Classifying buildings according to occupancy facilitates the ___
Administration of a code
IBC R-1 occupancy classification
Hotels and motels
IBC R-2 occupancy classification
More than 2 units; apartments, dorms, nontransient hotels
IBC R-3 occupancy classification
Not more than 2 units; Child care with 5 or fewer persons of any age less than 24 hours
IBC R-4 occupancy classification
Assisted living with 5-16 occupants
IBC A-1 occupancy classification
movie theater or concert hall
IBC A-2 occupancy classification
nightclub or restaurant
IBC A-3 occupancy classification
bowling alley, church, dance hall, exhibit hall
IBC A-4 occupancy classification
indoor sports arena
IBC A-5 occupancy classification
outdoor stadium
NFPA 5000
Building construction and safety code
NFPA 101
Life safety code
What are the 12 major occupancy classifications used by NFPA 5000 and NFPA 101.
Assembly, Educational, Day care, Health care, Ambulatory health care, detention and correctional, residential, residential board and care, mercantile, business, industrial, storage
Interior features of a building such as __, __, and __ have a cumulative effect on the outcome of a fire event
Wall coverings, compartmentation, and fire protection systems
Noteworthy examples of interior finish fires
LaSalle Hotel fire in Chicago (61 lives/1946) and the Beverly Hills Supper Club in Southgate, Kentucky (165 lives/1978)
Can an interior finish be a structural material?
YES, it may or may not be structural
In the international community the term ___ is used instead of interior finish.
interior lining; this term may ultimately replace interior finish in North America
Material is generally considered trim as long as it does not exceed __ of the wall and ceiling area and is distributed throughout the space so that it does not constitute a large continuous surface.
10%
Building codes usually exclude surface treatments such as paint and wall paper that are no thicker than __
1/28th an inch
The speed at which flame will spread over the surface of a material is referred to as the ___.
Surface burning characteristics of the material
The speed of flame spread is influenced by: (4 things)
The composition, orientation, and thickness of the material, ventilation, the shape of the space in which the material is installed, and whether the finish material is applied to the ceiling or wall
Because fire tests are an inexact science, test results have to be taken as ___
General guidelines
Flame spread for a Class A rating
0-25
Flame spread for a Class B rating
26-75
Flame spread for a Class C rating
76-200
Materials with a Class A rating are required in the ___ of most occupancies
vertical exits
Materials with a Class B rating are required in ___
Corridors that provide exit access
Class A, B, or C materials may be required in other rooms and spaces depending on the occupancy. The rooms of health care and assembly occupancies, for example, will require either ___ interior finish materials
Either Class A or B
Building codes generally allow an increase in the flame spread rating of interior finish materials in buildings equipped with __
An automatic sprinkler system
Heat Release Rate definition
Total amount of heat produced or released per unit time. the heat release rate is typically measured in kilowatts or megawatts of output
The ___ is the most commonly used method for evaluating the surface of burning characteristics of materials.
Steiner tunnel test
What are the formal identifications for the steiner tunnel test
ASTM Standard E84 and UL 723
What NFPA standard is the same as the steiner tunnel test?
NFPA 255, Standard method of test of surface burning characteristics of burning materials
What are the dimensions of the steiner tunnel test?
25 ft long, 17 and 1/2 inches wide, and 12 inches high
What are the flame specs for the steiner tunnel test?
5000 BTU flame
How long is the steiner tunnel test continued?
10 minutes
What two standard materials are steiner tunnel test results used as comparison?
Asbestos cement board (0) and red oak flooring (100)
How long does it take the flame to travel 24 ft for the red oak floor?
5.5 minutes
Flame spread rating for gypsum wallboard
10-15
Flame spread rating for treated douglas fir plywood
15-60
Flame spread rating for mineral acoustic tile
15-25
Flame spread rating for walnut-faced plywood
171-260
Flame spread rating for veneered woods
515 (approx)
What can pose difficult enforcement problems for inspectors in the field?
The fact that flame spread ratings of many materials cannot be determined in the field unless the manufacturer can be identified and contacted
What measures the visual obscurity for the smoke developed rating in a steiner tunnel test?
A photoelectric cell and a light source at the end of the tunnel furnace
Codes limit the max smoke developed to ___
450
What are some examples of fire retardant coatings? (4 things)
Intumescent paints, mastics, gas forming paints, and cementitious and mineral fiber coatings
Fire retardant coatings may not have a permanent effect if used in ___ or ___.
Exterior applications or environments with high humidity
Fire retardant coatings cannot be substituted for ___
Structural fireproofing
Which NFPA is a large scale test developed for evaluating the fire performance of textile wall coverings?
NFPA 265 Standard methods of fire tests for evaluating room fire growth contribution of textile coverings on full height panels and walls
NFPA 286
Another room corner test. “Fire tests for evaluating contribution of wall and ceiling interior finish to room fire growth”
Can the NFPA 286 test handle materials that may not remain in place?
Yes
What is the IBC NFPA 286 acceptance criteria? (how do you pass the room corner test?) (5 things)
- Noting whether or not the flames spread to the ceiling of the test chamber
- The flame cannot spread to the outer extremity of the sample
- Flashover cannot occur
- The peak rate of heat release cannot exceed 800 kW
- A maximum amount of smoke released
The degree of fire resistance required of a wall or partition will depend on its ___
Purpose
Another term for rated assembly is ___
Labeled assembly and fire rated
Fire walls are constructed with sufficient fire resistance and structural stability to act as an absolute barrier to a fire and structural collapse under conditions of ___
Total burnout on either side
Why are firewalls not popular with designers?
They increase structural costs, may interfere with the free movement of ocupants or material, they are achitecturally unattractive in occupancies where an expansive interior is desired
Some single family homes can be as close as __ apart
18 inches
Building codes typically allow elimination of fire walls when a building is equipped with an automatic sprinkler system if it meets criteria for __, __, and __.
Occupancy, height, water flow during fire conditions, and other code requirements
Firefighters can use an ___ as a protected vantage point from which to attack the main body of the fire.
Opening through a firewall
Firewalls can be constructed either as ___ or as ___.
Freestanding walls or as tied walls
Where are freestanding fire walls usually found?
in buildings of Type III or V construction, although they may also be used in other types of construction including type II
Freestanding walls must be designed to resist a lateral load of at least ___
5 pounds per square feet
Tied fire walls are erected at a ___
Column line in a building of steel frame or concrete frame construction
The IBC permits combustible structural members to be framed into a masonry or concrete fire wall from opposite sides provided there is a ___ separation between the ends of the structural members.
4 inch
The height of the parapet of a firewall above a combustible roof is determined by the building code and varies from ___
18 to 36 inches
Do some building codes provide exceptions for the parapet portion of a firewall?
YES
What is a common way of achieving 1 hour fire resistance separating apartment units.
5/8 inch fire rated gypsum applied to both sides of 2.5 inch steel studs; this assembly may or may not be used for a load bearing application
What is the main difference between the designations of enclosure wall and partition walls?
Their function; their construction is very similar, but enclosure walls block the vertical spread, and partitions block horizontal.
What is the fire resistance rating of enclosure walls?
1-2 hours, depending on the height of the building
Enclosure walls are usually ___ although load-bearing masonry stair enclosures are found in older mill buildings.
non-load bearing
___ enclosure walls can be found in older fire resistive buildings
Hollow clay tile
___ can prove troublesome for firefighters because they can provide a means of vertical communication of fire from ___
Light shafts; window to window
What is the design function of the curtain wall?
To separate the interior environment from the exterior environment
Curtain walls must also be designed to control __, __, and __.
Heat loss, noise transmission, and solar radiation
Curtain walls are often constructed using a combination of __, __ or __
Glass and steel, stainless steel, or aluminum. They may also be constructed of lightweight concrete, plastic, fiberglass, and a variety of metal panels with core materials such as expanded paper honeycombs and compressed glass fiber
The required fire resistance of curtain walls depends on the ___
Separation distance between buildings and the building occupancy
Fire doors can be found in industrial buildings dating back to the ___
End of the 19th century
Is the classification of a fire door the “fire resistance rating” or a “fire protection rating”
Protection rating. The other is used to describe structural components.
Letter classifications for fire door openings - Class A
Opening in fire walls
Letter classifications for fire door openings - Class B
Openings in vertical shafts and openings in 2-hour rated partitions
Letter classifications for fire door openings - Class C
Openings between rooms and corridors having a fire resistance of 1 hour or less
Letter classifications for fire door openings - Class D
Openings in exterior walls subject to severe fire exposure from the outside of a building
Letter classifications for fire door openings - Class E
Openings in exterior walls subject to moderate or light exposure from the outside
The 1/2 and 1/3 hour doors are primarily used in ___
Smoke barriers and openings to corridors
Doors rated at ___ are normally required for 2 hour rated vertical enclosures
1.5 hours
ASTM Standard for testing fire doors.
ASTM E-152, same as NFPA 252
Are the conditions for passing a furnace test for door assemblies as rigid as fire rated walls?
NO
What is the primary criterion for door assembly acceptance?
The door must remain in place
Doors with a ___ rating may not be subjected to the hose test depending on their intended application.
1/3 hour
What is included on the label for fire doors? (3 things)
Door type, hourly rating, and the identifying label of the testing laboratory
The hardware used on wood swinging fire doors is referred to as either ___ or ___
Builders hardware or fire door hardware. Fire door hardware is normally shipped with the door where builders hardware can be shipped separate.
For glazed windows in fire doors, ___ requires that each piece of glass installed in a fire door has a listing mark that is visible after installation.
NFPA 80, Standard for fire doors and fire windows
Until recently, only fire doors with ratings up to ___ were permitted to have glass panels but now doors with ratings up to ___ can be equipped with them.
1.5 hours; 3 hours
What is the max allowable area of glass in fire doors with 1, 1.5, and 3 hour ratings?
100 square inches
Usually, louvers in doors are closed by means of a ___
Fusible link
Swinging fire doors with ratings up to ___ can be equipped with louvers.
1.5 hours
Can louvers be installed in any fire door?
No, only doors that are listed for the installation of louvers
A door holder can be used with __, __, or __ fire doors
swinging, sliding, or rolling
A door operator is intended for use with __
sliding fire doors
A common type of sliding door is a __
metal covered wood core door
What are metals used to cover horizontal sliding doors? (3 things)
Steel, galvanized sheet metal, and terneplate (tin and lead composite)
Smooth galvanized sheet metal is used on wood core doors known as ___
Kalamein doors
Swinging fire doors are available with ratings of ___ to ___
1/3 hour to 3 hours
What are reasons for fire door failure? (3 things)
Damage to the door closure, the door itself, or door guides
___ doors which are used infrequently, are especially subject to damage
Overhead fire doors
Which chapter of NFPA 80 covers maintenance of fire doors?
Ch 15
The strength of wood varies significantly with __, __, and __.
Species, grade, and direction of load with respect to grain
Is wood stronger parallel or perpendicular to the grain?
Parallel
Allowable compressive strength parallel to the grain varies from __ to __ for commercially available grades and species of framing lumber.
325 to 1700 psi; Compressive strength
On the basis of strength to unit weight, wood has a tensile strength comparable to __
steel; although this is reduced for wood due to defects
Allowable tensile strength of wood is about __
700 psi tensile strength
Most structural lumber has a moisture content of ___
19 percent or less
Lumber is graded for both __ and __
Structural strength and appearance
Boards have a nominal thickness of ___ or less
2 inches
Dimensional lumber has a nominal thickness of ___
2 to 4 inches
Timbers have a nominal thickness of ___
5 inches or more
Dimensional lumber is available in lengths from __ to __ feet
8 to 24 feet
Actual size of a 4x4
3.5x3 9/16
Actual size of a 6x6
5.5x5 5/8
Actual size of a 2x6
1.5x5 5/8
What do the thickness of the individual laminations in glulam beams vary between?
3/4 inch to 2 inches
Laminated members can be produced in depths ranging from ___ to ___ and lengths up to.
3 to 75 inches, lengths up to 100 ft
What are the 3 types of joints for glulam beams?
Butt, scarf, and finger joints
Of the 3 types of glue joints, which one cannot be used to transmit tensile forces?
Butt joint
What are the three products that fall under the structural composite lumber category?
Laminated veneer lumber, parallel strand lumber, and laminated strand lumber
LVL finds application in ___.
I-Joists and beam sections 1 3/4 to 3 1/2 inches thick
LVL is made from __
The outer portions of the log
Parallel strand lumber is made from the outermost veneers peeled from a log that are not as uniform as those used in LVL. These veneers range from __ to __ feet in length and produce odd-shaped strands that are coated with an adhesive and cured under pressure.
2 to 8 feet
Which of the three Structural Composite Lumber (SCL) products is the strongest?
Parallel strand lumber (PSL); used for heavily loaded columns and long spans
Laminated strand lumber is produced by taking long strands of wood up to __ in length and bonding them with a resin in a steam pressing process.
12 inches; LSL is typically used for short-span beams and columns
The exterior veneers of plywood have their grain oriented in the __ of the sheet.
Long dimension
What are the thickness of individual layers for plywood?
1/16 to 5/16 inch
What are the nominal thickness of plywood panels?
1/4 inch to 1 1/8 inch
Nonveneered panel products include __, __, and __.
OSB, particleboard, and waferboard
How many layers in OSB?
3 to 5
How large can the individual particles in particleboard be?
1 inch
Particleboard can be manufactured in sizes up to ___
8 by 40 feet
Particleboard is used for ___
Flooring in manufactured and mobile homes
Waferboard has been largely replaced by __
OSB
The foam plastic in SIP panels is usually __
Expanded polystyrene
The inner core of a SIP panel can be up to __ thick.
1 foot
What does the span rating 32/16 indicate?
Can be used as roof sheathing on rafters 32 inches apart or as subflooring on joists 16 inches apart
Heavy timber trusses are made up of members up to __
8 or 10 inches
What are frequently used at the connection points for heavy timber trusses?
Steel gusset plates with through bolts
Wood I-beams are frequently used for __
Floor joists; also used for rafters in the framing of roofs.
The flanges of an I-beam can be made of __ or __.
Laminated veneer lumber or solid wood lumber
The relative hazard posed by a combustible material such as wood is a function of several variables including __ (3 things)
Ignition temperature, heat of combustion, and the ratio of the surface area to mass
Ignition temperature of wood is affected by the following variables: (6 things)
Density of the wood, size and form of the wood, moisture content, rate of heating, nature of the heating source, and air supply
At what temperature does pyrolysis begin?
Somewhere below approx. 392 degree F
What is defined as the total amount of thermal energy that could be released if the fuel were completely burned.
Heat of combustion
Building codes permit the use of fire retardant treated wood for certain application in ___ and ___ construction
Fire resistive (type 1) and non combustible (type 2)
The IBC allows fire retardant treated wood in non load bearing partitions where the required fire resistance is __
Two hours or less
What are the two main methods of fire retardant treatment?
Pressure impregnation and surface coating
Surface coating with a fire retardant mainly is used to reduce ___
The flame spread rating
Any of the following chemicals may be used as a fire retardant treatment: (6 things)
Ammonium phosphate, Ammonium sulfate, boric acid, zinc chloride, sodium dichromate, and borax
How do most fire retardant chemicals work?
By accelerating charring
What ASTM is the standard rain test for exterior fire treated lumber?
ASTM D2898
Does fire treating lumber reduce the strength?
YES
What is the flame spread rating of thermoplastic composite lumber?
80
Heavy timber framing uses columns not less than __
8x8 inches
Because of labor costs and limitations in the basic strength of wood, most wood frame buildings do not exceed __ stories
Three
Beams in heavy timber construction are not less than __
6x10 inches; except roof beams, they can be smaller
Fire resistance equation for heavy timber exposed on 3 sides. This equation works for timbers 6 inches or greater.
t = 2.54ZB[4-(B/D)] —- t is the fire resistance in mins Z is the load factor B and D are width and depth
In the design of connections for heavy timber construction, what factor does the engineer need to consider? (4 things)
Specific gravity of the wood, shrinkage of the wood, position of fasteners relative to the grain of the wood, and relative size of the wood members and the fasteners
Information available from the US department of agriculture indicates that the heat of a fire has ___ on the adhesives that are used in contemporary glulam beams.
Essentially no effect
How far apart are the posts generally spaced for post and beam framing?
4 to 12 feet
The posts for post and beam framing are usually sizes of __ or __
4x4 or 6x6
The floors in light wood framing are supported by __, __, or __.
Solid joists, truss joists, or wood I-joists
What are the two types of light wood framing?
Balloon framing and platform framing
Balloon framing has the advantage of ___
Minimizing the effects of lumber shrinkage that can occur over time as the lumber dries and loses its moisture content
Does shrinkage of lumber occur more with the length or the cross sectional dimensions?
Cross sectional dimensions
Balloon framing has not been widely used since __
the 1920s
Platform framing is also called ___
Western frame construction
Are platform or balloon frame buildings easier to erect from a construction standpoint?
Platform
Firestopping can consist of various materials including ___ (5 specific things)
2 inch nominal lumber, gypsum board, cement fiber board, batts or blankets of mineral wool, glass fiber, or other approved materials
Name 4 locations where fire stopping is required per building codes.
- Within stud walls at the ceiling and floor levels,
- At the interconnections between vertical stud wall spaces and horizontal spaces created by floor joists or trusses,
- Between stair stringers,
- Behind soffits
Building codes require ___ in the attic spaces of combustible construction.
Draft stopping
Draft stops are also called __
Curtain boards or draft curtains
The usual requirement is for an attic space to be divided into area of ___.
3000 square feet
The most common sheathings are ___ (4 things)
Plywood, OSB, particle board, or exterior gypsum sheathing
Asbestos sidings were commonly used from the __ until the __
1930s to 1970s
How often must a brick veneer exterior be tied to the wood frame of a wall?
Intervals of 16 inches
What is a frequently used rule to determine if a brick wall is bearing or veneer?
Every sixth course of brick is a header course with the ends of the brick facing out with a bearing wall; however some masonry bearing walls will use a horizontal tie instead of a header course
How would a small wood building with no interior finish material be classified under the building codes?
Type V-B
Where might impact resistant gypsum board be used?
Correctional or school facilities, made with fiber glass mesh
Requirements for ignition resistant construction include features such as ___
Fire resistant roof coverings to protect against flaming embers
What are some unique causes to wood that make it vulnerable to deterioration? (3 things)
Insects, Decay, and shrinkage
What is a drawback to the use of masonry?
Laying individual units is labor intensive, and long term deterioration of mortar joints
Masonry units can be made of several materials, including the following: (7 things)
Brick, Terra cotta, Concrete block, Stone, Clay tile block, Gypsum block, Glass
Bricks are produced from a variety of locally available ___
Clays and shales
What is the hardness of brick dependent on?
The soil used in its composition
A kiln used to fire bricks will have temperatures up to ___
2400 degrees F
How long does the firing process for bricks take?
40 to 150 hours
What is a typical brick size?
3-5/8 by 7-5/8 by 2-1/4
For most brick sizes, three courses of brick plus the intervening mortar joints equals a height of __
8 inches
What is the most common size of concrete block?
8x8x16
In addition to the hollow block, concrete masonry units can be produced as either __ or as __
Bricks or as solid blocks
What are the most common types of stone used in construction? (5 types)
Granite, limestone, sandstone, slate, and marble
Brownstone is a form of __
Sandstone
Masonry units have no significant __
Tensile strength
The allowable compressive strength of brick masonry would be __
250 psi
Density and compressive strength of a brick
100-140 lb/cu ft; 2,000 to 20,000 psi
Density and compressive strength of a concrete masonry unit
75-135 lb/cu ft; 1,500 to 6,000 psi
Density and compressive strength of limestone
130 to 170 lb/cu ft; 2,600 to 21,000 psi
Density and compressive strength of granite
165 to 170 lb/cu ft; 15,600 to 30,800 psi
Density and compressive strength of sandstone
140 to 165 lb/cu ft; 4,000 to 28,000 psi
How much would an 8 inch thick 4’x4’ brick wall weigh?
1267 lbs
What is the range of compressive strength for mortar?
75 psi to 2,500 psi
Most mortar is produced from a mixture of ___ (4 things)
portland cement, hydrated lime, sand, and water
When was sand-lime mortar commonly used?
Until the 1890’s
Older masonry construction that made use of sand-lime mortar must ___
Be repaired with sand-lime mortar
How can master streams weaken mortar?
Either from the pressure of the stream or from the flushing effect of water
What does portland cement consist chiefly of?
Calcium and aluminum silicates
What are load bearing masonry walls constructed of? (3 options)
Brick, concrete block, or a combination of the two
When used as a supporting wall, the thickness of masonry walls varies from a minimum of ___ to ___.
6 inches to several feet
Non-reinforced masonry walls are usually limited to a maximum height of around __
Six stories
In contemporary practice, when a building is to be more than __ or __ stories tall, the use of a steel or concrete structural frame is usually more economical than erecting a nonreinforced masonry bearing wall
Three or four stories
By using reinforced masonry, it is possible to construct load-bearing masonry walls to a height of __ having a wall thickness of only __
10 stories or more; 12 inches
Horizontal layer of individual masonry units
Course
Single vertical row of multiple rows of masonry units in a wall, usually brick.
Wythe
Course of bricks with the ends of the bricks facing outward.
Header course
When bricks are placed end-to-end they create a __
Stretcher course
If bricks are placed vertically on end, a __ is created
Soldier course
In the case of a cavity wall, the placement of __ is especially important because the use of a brick header course usually is not practical.
Metal ties
Support of the masonry over an opening is accomplished by the use of a __, __, or __.
Lintel, an arch, or corbelling
Lintels are frequently __ but also can be __ or __.
Steel beams; reinforced concrete or reinforced masonry
Why is wood not used for lintels in modern construction?
Shrinkage problems
If the height of the wall above the opening is shorter than the height of the triangular section, it is assumed that the lintel must ___
Support the entire weight of the masonry above the opening.
Corbelling is only used where ___
The architectural style makes it attractive
Is a parapet wall only for appearance?
No, it can also be required by building code to provide a barrier to the communication of fire between closely spaced buildings
Parapets project from __ to __ or more above the roof, usually without lateral support
1-3 feet or more
A ___ may be used with masonry construction to provide additional support where beams exert additional force.
Pilaster
Ordinary construction is also known as __
Masonry, wood joisted—type 3
In modern practice __ and __ are often used in place of the traditional solid joists and rafters
Truss joists and wood roof trusses, NOT I joists like I keep thinking
With interior framing of masonry buildings, travel of fire through the floor and ceiling spaces should be anticipated just as with wood frame construction, especially where __
Truss joists are used
In many applications such as residential and small commercial buildings, wood joists or beams simply rest on the masonry wall in an indentation known as a ___
Beam pocket; a metal strap may be provided to function as a horizontal tie between the masonry and the end of the beam.
The fire resistance of a masonry wall depends on the __ and the __
Type of masonry units used and the thickness of the wall
Walls constructed of fire rated concrete masonry units or bricks can have fire resistance ratings of __ to __
2-4 hours or more
A massive masonry wall, ___ or more in thickness will have an inherently high degree of fire resistance
18 inches
Does the presence of tie rods mean that a building has undergone repair?
Not necessarily, the tie rods may have been part of the original construction
Masonry walls usually collapse as a result of ___
The collapse of the interior wood framing
What are the two things that distinguish Type 4 from Type 3 construction.
The dimensions of the wood structural members are bigger and combustible concealed spaces are not permitted
In mill construction, FLOORS are required to be __ tongue and groove with __ nominal tongue and groove flooring.
3 inch; 1 inch
In mill construction, ROOFS are required to be __ tongue and groove or __ structural panel or planks.
2-inch; 1-1/8
In mill construction, nonbearing WALLS AND INTERIOR PARTITIONS are required to be not less than __ or __
Two layers of 1-inch matched boards or laminated construction 4 inches thick or 1-hour fire rated construction
The firefighter must understand that the behavior of steel under fire conditions depends on __ and __
The mass of the steel and the degree of fire resistance provided.
Firefighters should understand that the protection of steel depends on __ (4 things)
The integrity of installation, protection methods, maintenance, and failure points
The basic properties of steel are as follows: (4 things)
- Strongest of the building materials,
- Non-rotting, resistant to aging, and dimensionally stable,
- Consistent quality due to controlled industrial process used in its manufacture,
- Relatively expensive, but strength and qualities enable it to be used in smaller quantities than other materials.
Common structural steel has less than __ of one percent carbon.
three tenths of 1% — 0.3%
What additive is added to steel to increase strength?
Molybdenum
How much carbon does cast iron have?
3 to 4%
What temperature are ingots brought to when rolling steel into shapes?
2200 degrees F
Cold rolled steel is used for members that have a __
Thin cross section, such as floor and roof decking and wall studs.
Can CRS studs be used for exterior bearing walls?
YES
What is the approx. yield point for A36 structural steel?
36,000 psi
Steels for special application, such as those used in bridge strands, have strengths as high as ___ but have very little ductility.
300,000 psi
What are two inherent disadvantages of steel?
It rusts and loss of strength when exposed to the heat of fire
What can steel be coated with to prevent the formation of rust? (3 things)
Rust inhibiting paint, zinc, and aluminum
At 1000 degree F the yield point of steel drops from 36,000 to ___
18,000 psi
At 1200 degree F the yield point of steel drops to approx. __ a loss in strength of approx. ___
10,000 psi; 72 percent
The speedwith which unprotected steel fails when it is exposed to a fire depends on several factors, including the following: (5 things)
- Mass of the steel members
- Intensity of the exposing fire
- Load supported by the steel
- Type of connections used to join the steel members
- Type of steel
Steel has a density around __
490 lbs per cubic foot
The amount of expansion for slender steel members, such as beams and columns, can be determined through a property known as the __
Linear coefficient of thermal expansion.
If an unrestrained steel beam 20 feet long were heated from 70 to 1000 degree F, it would expand __
1.4 inches
In most fire situations, is yielding steel or the thermal expansion of steel more significant?
Yielding steel; This causes bending and buckling which is of more concern
Beams and columns in steel-frame buildings are connected by one of two methods:
Bolting or welding; Riveting was used in the early 1900s but is no longer practical
The connection of a beam to a column not only transfers loads between members but also __
Determines the rigidity of the basic structure
Beam and girder steel frames can be classified as __, __, or __.
Rigid, simple, or semi-rigid
What type of connection is designed to resist the bending forces resulting from the supported loads and lateral forces?
Rigid frame connections
With simple frame, the joints are designed primarily to support a __
Vertical force
Steel beams and trusses supported by a masonry wall are examples of __
Simply supported systems
Ideally a shear wall should be continuous from the foundation of the building to the __ (semi-rigid frame)
Highest story at which it is needed
What do semi rigid frames use for lateral stability?
Diagonal bracing or shear panels
What are three dimensional space frame steel trusses also referred to as.
Delta trusses
Two commonly encountered applications of the basic steel truss are __
Open web joist and the joist girder
Open web joistsare mass produced and are available with depths of up to __ and span up to __. More frequently sized?
6 feet and 144 feet; However, more frequently found with depths less than2 feet and spans of 40 feet
When round bars are used for the diagonal members, the open web truss is known as a __
Bar joist
Bar joists are frequently used in __
Closely spaced configurations for the support of floors or roof decks
Joist girders are heavy steel trusses used to take the place of ___ as part of the primary structural frame.
Steel beams
Steel rigid frames usually are used for spans from __ to __ feet.
40 to 200 feet; for steel rigid frame buildings
The top of the steel rigid frame is known as the __ and the point where the inclined members meet the vertical members are known as the __
Crown; knees
Do the vertical members of steel rigid frame buildings need to be rigidly connected to the foundation.
No, they can be, but they do not have to be. This will depend on anticipated wind loads
Steel arches can be constructed to span distances in excess of __
300 ft
Steel arches can be designed as either __ or __.
Girder arches or trussed arches
Bridge cables can have strengths as high as __
300,000 psi
The possibility of __ is greater with steel columns than with columns made of other materials.
Buckling
A property of a given column, known as its ____ is used in combination with the condition of the column end to determine the load that can be safely supported without buckling
Slenderness ratio
The slenderness ratio is a number that compares the __ to the __
The unbraced length of a column to the shape and area of its cross section. The higher the number, the more likely buckling will occur.
In general, columns used for structural support in buildings should not have a slenderness ratio greater than __
120
What are the three methods steel members can support floors in multistory buildings?
Open web joists or trusses, steel beams, and light gauge steel joists
When lightweight concrete is used for floors in steel frame buildings, what is the minimum thickness of the concrete?
2 inches
How are light gauge steel joists produced?
From Cold rolled steel
Light gauge steel joists are produced with depths of __ to __ inches and can be spaced __ to __ apart.
6 to 12 inches spaced 16 to 48 inches apart
In gabled rigid-frame structures what will be the strongest part of the frame and the last part to fail?
The knee joint between the roof and the wall
A steel column encased in __ of concrete with a siliceous aggregate would have a fire resistance of 4 hours
3 inches
In contemporary practice, the most commonly used insulating materials for steel are (4 things)
gypsum, spray-applied materials, and intumescent coatings; sometimes lightweight concrete
SFRMs
Spray applied fire resistive materials
Which type of gypsum board is usually required where a specified fire resistance is desired?
Type X
Gypsum consists of approx. __ percent entrapped water.
21 percent
What are the most common types of SFRMs?
Mineral fiber or expanded aggregate such as vermiculite and perlite
The applied fireproofing can vary from __ to __ inches to produce a fire-resistive rating of 1 to 4 hours
7/8 to 1-7/8 inches
Low density fiber materials for spray applied materials are not suitable for __
Exterior use; Use materials that have densities greater than 20 lb/cu ft
High density SFRMs that use magnesium oxychloride have densities ranging from __ to __
40 to 80 lb/cu ft
Spray applied cementitious materials have densities varying from __ to __
15 to 50 lb/cu ft
It is very important that supports and hangers be installed __ application of SFRMs
Before
An intumescent material will __ when heated (3 things)
Char, foam, and expand
An intumescent material will expand __ to __ times its original volume
15 to 30 times
What is the application thickness of intumescent materials?
0.03 to 0.4 inches
The use of a membrane ceiling (drop ceiling) can provide a floor and ceiling assembly or a ceiling and roof assembly with af fire rating of __ to __ hours
1 to 3 hours
What is a common code modification for fire resistive construction?
Eliminating the fire resistance rating for roof construction located more than 20 feet above the floor below for some occupancies
An advantage of the use of concrete is that __
It can be produced from raw materials that are usually locally available and are low in cost
Curing fresh concrete requires correct __ and __
Hydration and temperature control
Hardening of concrete involves a chemical process known as __
Hydration
Concrete can be kept moist by several techniques including __ (4 techniques)
Sprinkling it with water, ponding, or covering it with a plastic film. Sealing compounds are also available that form a membrane on the concrete to slow evaporation
Concrete that is curing must be maintained at the correct temperature, ideally between __ and __
50 and 70 degrees F
Concrete that is cured at or above __ will not reach its proper strength.
100 degrees F
Normal design strength of concrete is reached after ___
28 days
An admixture known as a __ can be used to produce a mixture that flows more freely.
Superplasticizer
What is a safety reason for coloring concrete?
When it is placed over buried electric cables
What can the ultimate compressive strength of concrete vary from?
2,500 to 6,000 psi
What are the two techniques used to reinforce concrete?
Ordinary reinforcing and prestressing reinforcing (prestressing is classified for both pretensioning and posttensioning reinforcement)
The diameter of standard size reinforcing bars vary from __ to __
0.375 inches to 2.257 inches
Vertical reinforcing bars are known as __ and are provided to __
Stirrups; resist the diagonal tension
Does the steel in a concrete beam only resist tensile forces?
No, it can also be used to support some of the compressive forces and also resist bending forces
What is provided to prevent vertical reinforcing bars from buckling?
Lateral reinforcing around the vertical bars
The forces that are initially applied in the prestressing process are ___ than the forces theoretically needed to support the concrete and the applied loads.
Slightly higher
Reinforcing steel in concrete should generally not be cut unless __
It is necessary to rescue trapped victims
Is it more dangerous to cut reinforcing steel in pretensioned or post tensioned concrete?
Post because the steel is not bonded to the concrete
If concrete is vibrated excessively as it is placed in the forms, __
Segregation of the aggregate results; the coarse agg goes to the bottom and the water and cement rise to the top
What is the single most important factor in determining the ultimate strength of concrete?
The water to cement ratio
What are the two methods to perform quality control of concrete?
The slump test or the compression test
The following are common cast in place structural systems. (3 systems)
Flat slab, slab and beam, and waffle construction
In flat slab concrete frames the slab varies in thickness from __ to __ inches
6 to 12 inches
Where do shear stresses develop in flat slab frames?
Where the slab intersects the supporting columns
With flat slab frames, in a building that will have heavy live loads, the area around the columns is reinforced with additional concrete in the form of __ or __
Drop panels or mushroom capitals; If there are light loads and these are not needed the system is known as flat plate
Slab and beam concrete framing is __ and is best suited for buildings with __
Extremely light weight; light floor loads
With slab and beam concrete framing, the slab can be as thin as __
2 inches
Slab and beam framing is sometimes referred to as __
Concrete joist construction
For slab and beam framing, the two-way framing system is used where spans are __ and floor loadings are __
short; high
What are some advantages of using precast concrete? (3 things)
Higher degree of quality control, Work can proceed more quickly at the job site, and they can be produced using a polystyrene core
When did precasting concrete become more common?
After WW2
With precast concrete, solid slabs are used for short spans up to approx. __ while the tee slabs can be used for spans up to __.
30 feet; 120 feet
Tilt up walls can be __
Several stories high
Tilt up walls can support several types of roof including __ (4 things)
Timber beams, precast slabs, steel beams, and steel trusses
A variety of techniques, such as __ can be used to connect precast structural elements. (3 things)
Bolting, welding, and posttensioning
What is a corbel?
Also known as a bracket, is a ledge that projects from the column and supports the beam
A very common application of precast concrete is in the construction of __
Parking garages
Are prestressed or ordinary reinforced concrete systems more vulnerable to failure?
Prestressed
High strength steels, like those used in prestressed concrete, have lower yield point temperatures than can be around __
752 degrees F
Concrete structural systems can have fire resistance ratings from
1-4 hours
The fire resistance of a concrete assembly is affected by the following variables: (5 things)
Concrete density, concrete thickness, concrete quality, load supported, and depth of concrete over reinforcing bars
Is structural lightweight concrete or ordinary concrete a better insulator?
Structural lightweight because it has a lower thermal conductivity; however it is not used for load bearing members
What is the primary cause of spalling?
The expansion of excess moisture within the concrete when it is either heated or when it freezes.
The extent of spalling depends on __
The amount of excess moisture and the length of time that has passed since the concrete was placed
Is new concrete or old concrete subject to more severe spalling?
New concrete
What is the effect called where concrete will absorb heat from a fire and then slowly release it after the fire is extinguished?
Heat sink effect
Is the heat released from concrete after a fire enough to reignite combustibles?
NO, but it can make overhaul uncomfortable
What are the three styles that roofs can be classified into?
Flat, pitched and curved
What direction is the typical light slope of a flat roof?
Typically from front to rear
Which style of roof are the easiest for firefighters to work?
Flat roofs
How are pitched roofs classified?
Low slope and medium to high slope roofs
What is the slope of a low sloped roof?
Less than 3 to 12 pitch
Medium to high slope roofs have slopes of __ to __.
4/12 to 12/12
Some structures, such as certain churches and mansions, have roofs with slopes of __ or greater. Too steep to work from a roof ladder.
18/12 or greater
The style of a pitched roof is determined by __ (3 things)
Climate, function, and aesthetic considerations
What is the simplest pitched roof?
The shed roof that only slopes in one direction
The hip roof slopes in __ directions and has a degree of slope similar to the gable roof
Four directions
The __ roof slopes in two directions, but there is a break in the slope. They are functional because the space created can be used for attic or living space.
Gambrel
The __ style roof forms a projection beyond the building wall that creates a concealed space through which a fire can communicate.
Mansard roof
The butterfly roof is a roof style that slopes in two directions – basically two shed roofs that meet at their __
Low eaves
A monitor roof is designed to provide __ and __
Light and ventilation; similar to an exaggerated lantern roof
The openable windows of a monitor roof are known as __
Clerestories
Monitor roofs were once very commonly used on __
Factory buildings
The windows of sawtooth roofs should ideally face __ because the light is more constant and the glare of the sun can be avoided
North
Curved roofs are most frequently supported by __ and __
Arches and Bowstring trusses
More architecturally spectacular curved roofs can be created using __ or __
Geodesic domes or Lamella arches
Lamellas vary from __ to __ and in lengths varying from __ to __ feet
2x8 to 3x16 inches; 8 to 14 feet
The short lamellas are bolted together in a diagonal pattern with a special plate known as a __
Lamella washer
Lamella arch roofs have been used for occupancies such as __ (3 things)
Gymnasiums, exhibition halls, and auditoriums
A geodesic dome is created using __
Spherical triangulation
A geodesic dome can be constructed from __ (6 things)
Wood, steel or concrete as well as plywood, bamboo, and aluminum
__ are designed to create extra living space and allow additional light into the structure.
Dormers
Because roofs are designed for lighter live loads than floors are, it is not unusual for modern flat roofs to __ as personnel walk across them.
Deflect or vibrate noticeably
Deflection and vibration of flat roofs is an indication of __
Lightweight roof construction
What is the primary difference in an inverted roof from a flat roof?
The location of their main roof beams
With an inverted roof, the main joists are located at the level of the ceiling and a framework is constructed __ to support the roof deck.
Above the main joists
Rafters are the standard supports used in __ style roofs, although trusses can also be used for these roof types. (5 types)
shed, gable, hip, gambrel, and mansard style roofs
The outward thrust of the rafters is resisted by __ or __ that are in tension.
Ceiling or attic floor joists or collar beams
If the architect desires to leave the underside of the roof exposed without joists, a ___ must be used to support the rafters.
Structural ridge beam
Wood rafters vary in size from __ to __ and can be spaced from __ to __ inches apart.
2x4 to 2x14 inches and 12 to 24 inches apart
What makes trusses vulnerable to early failure under fire conditions?
The reduced mass and the interdependence of components
A __ truss is common in residential type construction.
Fink truss
What kind of truss has all chords and diagonal members in the same plane?
A common truss, also known as monoplane truss
With Lightweight trusses that are gang nailed the individual members would be wooden __ or __ and individual trusses would be spaced __ to __ feet apart
2x4s or 2x6s and 2 to 4 feet apart
A bowstring truss assembly uses __ at all joints except the heel plates located at the ends of the truss.
Split ring connectors
What are the most common style trusses used for pitched roofs? (steel and wood)
The Fink and Pratt style
An arch can be constructed from __ (3 things)
Masonry, laminated wood, or steel
The behavior of a roof supported by an arch is basically determined by the __
Material from which the arch is constructed
The components of roof decks include: (3 things)
Sheathing, roof planks or slabs, and purlins
When does a roof deck serve as the roof support?
With concrete deck roofs
Wood panel roof decking may have a thickness of __ on supports __ on center.
1/2 inch; 24 inches on center
Wood planks for roofs will have a minimum __ nominal thickness.
1 inch
Corrugated steel used in roof decking ranges from __, the thinnest to __ , the thickest.
29 gauge to 12 gauge; the overall depth varies from 3/4 to 2 inches
What is cellar decking?
When a sheet of flat steel is welded to the bottom of corrugated steel decking
Gypsum has the advantage of being __
Nailable; precast concrete can also be nailable with the appropriate aggregate
What interval might nailing strips be placed in cast in place roof decking?
Intervals of 3 feet
The type of roof covering used depends on the __ (4 things)
Form of the roof structure, the slope of the roof, the local climate, and the appearance desired
Will fog corrode a metal roof?
YES
Which type of roof usually has a more complex roof covering, flat or pitched?
Flat, because they drain more slowly
A flat roof usually consists of several component layers such as __ (6 things)
A vapor barrier, thermal insulation, roofing membrane, drainage layer, and wear course, roof decking
When is a vapor barrier needed?
When the average outdoor temperature is below 40 degrees F and the indoor relative temperature is 45 percent or greater at 68 degrees F
What can the vapor barrier be made of? (4 things)
plastic, aluminum foil, kraft paper laminated with asphalt, asphalt saturated roofing felt
What are the three general categories of membrane roofs?
Built up roof membranes, single-ply membranes, and fluid-applied membranes
How many layers of roofing felt is a common design for built up membranes?
FOUR layers
How long do built up roofs usually last?
20 years
What are typical sizes of single ply membrane material?
Sheets 10 or 20 feet wide and up to 200 feet long with thin thickness of 0.03 to 0.10 inches.
What is the most common single ply membrane material?
A synthetic rubber material, ethylene propylene diene monomer (EPDM), other materials are PVC and CPE
Can single ply membranes accommodate for shifting in a building?
Yes because it stretches
How are single ply membranes attached to the roof? (3 ways)
By adhesives, gravel ballast, or mechanical fasteners
What are some materials used for fluid applied roof membranes? (4 things)
Neoprene, silicone, polyurethane, and butyl rubber
The drainage layer of a roof can be __ (3 things)
The ballast layer in a single ply roofing system, a drainage fabric, or the aggregate used in a built up roofing system
The wear course may also consist of __ when the roof is used for pedestrian traffic
Deck pavers
What are the two broad categories for the roof coverings on pitched roofs?
Shingle and metal roof coverings
The difference between wood shingles and shakes is in their __
method of production
Shakes are split from the wood either by hand or by machine and are __
thicker than shingles; shingles are sawn from pieces of a tree trunk
Wood shingles and shakes in north america are made from __, __ or __.
red cedar, white cedar, or redwood because they resist decay
