Building Construction Flashcards
What are the 6 types of roofs?
HBFAGS
Hip, Bridge, Flat, Arched, Gable, Sawtooth
What does conventional construction utilize?
Structural members that depend on its size for strength (4x8)
Depends on its size for strength
What does light weight construction utilize?
Does not derive the size of its members for strength. Strength is derived from multiple members that are under compression (top cord) and tension (bottom cord)
What is the fire behavior of light weight construction?
Because it utilizes the sum of its member for strength, it can fail quickly. If one member fails, others may fail
Size of light weight truss members
70 feet and typically comprised of 2x4s or 2x3s
Conventional construction consists of
Minimum 2x4 and up
Gable roof consists of
Conventional or ordinary construction utilizing Ridge board or rafters that cross the outside walls. Collar beam and ceiling joist
Rafters on gable roof consist of
2x6 or larger and are usually 16 to 24 inches “on center”
Metal Gusset Plates are what sizes typically
18 gauge steel plates that offer 3/8 inch penetration
Strengths of conventional construction
utilizes ridge boards and rafters of 2 x 6 inches or larger. This type of construction will last
longer (compared to 2 x 4 inch trusses) when exposed to fire
the strong area of the roof are the ridge and the area where rafters cross the outside walls
Hazards of conventional construction
2x4 rafters w/ no ridge boards may lead to early failure of roof
gusset plates can lead to early failure
when metal connectors fail, so will the wood members
strength of hip roof
Ridge board, valley rafters, hip rafters, and the area where rafters cross the outside walls are areas of strength. In
conventional construction, ridges and rafters are 2 x 6 inches or larger.
hazards of hip roof
roofs with steep pitch may require roof ladders and can be slippery and offer minimal footing when dry
bridge truss roofs are found where
commercial buildings primarily constructed during the 1930s and 40s
Which cord is under compression and which cord is under tension in a bridge truss roof
top cord compression and bottom cord tension
if a bridge truss roof fails, it typically fails-
in sections
hazards of bridge truss roof
the bottom
chords can be covered with sheathing or plywood) (and/or lath and plaster, etc. can be attached to the bottom of chord of
the trusses. These factors can contribute to early collapse of the trusses and roof.
lumber size for bowstring arch roof types
2x12 or 2x14
lamella arch roofs are commonly found where
gymnasiums, large
buildings used for recreational activities, large supermarkets, etc
roof decking of lamella arch roofs is comprised of what
1 x 6 inch sheathing and composition roofing material
total roof collapse will occur with if fire removes more than what percent of the roof of lamella arch roofs
20%
ties truss arch roof types are identified by what
visible tie rods that pass through outside plates
Light weight truss structural members can span how many feet
70
Ridge board on a gable roof is typically what size
1x6
Rafter size on conventional gable roof
2x6
Bowstring lumber of arch truss
2x12 or 2x14
Types of arched roofs
Bowstring, lamella, tied truss
Beam size for panelized roof
6x36
Common size of purlins on panelized roof
4x12
Components of panelized roof
Beams (laminated, wood, or metal)
Purlins
2x4 inch joists
2 inch plywood decking
Bottom chord of open web bar joists size
1/8 inch steel
Web support size of open web bar joists
5/8 inch steel bar
A steel or wood substructure roof covered by corrugated metal is called
Robertson decking
Concrete tilt up can be up to how many stories
5 stories
Gable:
Rafters and “on center”
2x6 or larger
16 to 24in on center
Bridge truss roof utilizes _____ sheathing
Diagonal
