202aA - 202bB - Roof/Truss Framing Systems Flashcards
Is a flat roof member a ceiling joist?
No it’s a roof joist
Why do we need look out joists on flat roofs?
Maintain same overhang on whole building; similar to hip jacks on a hip roof….but flay
Do we need a centre drain on parapet flat roofs?
Yes. Water can’t drain past the parapet built up border
Which roofs typically have ONE sloping surface?
Shed
When do we need TWO birds mouths?
Shed/single slope roofs
Do gable roofs have TWO slopes?
Yes
Do hip roofs have FOUR slopes sides?
Yes
What types of rafters are used for gambrels?
Only common rafter style cuts
Mansarda have EIGHT surfaces?
Yes
What does a dutch roof combine?
Gable roof leading into a hip slope
What’s an “inverted gable called? Looks like an insect
Butterfly roof
What two roofs does a monitor roof combine?
Gable and shed
Do dormers add livable space?
They can. Similar to an intersecting roof but built into a major roof
Rake rafter two synonyms
Fly rafter
Barge rafter
Common
Barge
Dropped gable
3 typical rafters on a gable roof
Is fascia on all 4 sides of a gable roof?
No, just two along building length
Do collar ties provide intermediate support or tie rafters together?
Intermediate support
What pieces do we frame in order to sheet a gable end face?
Gable studs
What is different between a theoretical line and a rafter IRL?
Rafter = theoretical - shortenings based off material sizes and thicknesses
Ridge
Birdsmouth
Fascia
3 working points on rafter latout
Seat and plumb
2 cuts on a roof
Single Cheek/bevel, double cheek/double bevel
Types of bevels you account for material meeting points on a roof
Is the roof span between opposing birdsmouth plumb cuts?
Yes
Is rise measured from birdsmouth seat cut?
Yes
Is ridge Center to BM plumb the roof
Yes
what is the wood left over after making a BM seat cut?
Wood above plate WAP
Close; no overhang
Open: sloped overhang no soffit
Sloped box: sloped overhang with soffit
Flat box: flat overhang for soffit underneath
4 main cornices
Do cornice returns transition the flat eaves soffit to the sloped eaves at the end of a gable?
Yes
Why do we need frieze boards on close cornices?
No overhang so need to transition from siding to shingle overhang
Sqrt of (rise/run)^2 + 1
SGF90
Sqrt of (rise/run)^2 + 2
SGF45
SIMILAR TRIANGELES can be compared with roof slope?
Yes. Rise/run = x/horizontal measurement….sub for rise
How do we quack and easy get a COMMON or HIP JACK rafter length?
Run x SGF90
Is line length and total line length the same?
No. TLL adds on line length of BM plumb cut to outside of fascia at overhang
Ridge
BM plumb
Fascia
3 working points on theoretical measuring line (LINES ON A BLUEPRINT)
Can we use stair gauges for the same cuts on rafters?
Yeah, keep angles the same
What’s stair gauges set at 100mm on tongue and 400mm on body?
A 3:12 roof pitch
Do we measure down material edges for shortenings?
Never. 90deg from plumb or seat cuts
1) working points
2) mark plumb lines at each
3) shorten 1/2 ridge at top
4) shorten full fascia at bottom
5) layout BM with 1/3:2/3 rule along PLUMB line
Basic steps to layout common rafters
Do we need to subtract 10mm from a seat cut when we need to shorten for fascia height?
Yes. Shrinkage
Given a seat cut length, how do we put it in a BM?
1)Measure 90deg from plumb line the required distance
2) plumb a line from the end of that point
3) make seat cut where it intersects board edge
Building length + overhang on each end
Ridge length
Splice ridges at opposing rafters?
Yes
Gussets to join common rafters when no ridge material?
Yes
Can we use SGF For gable studs?
Nope! Compare triangles!
Rise/run = x/y
Do we need to account for theoretical lines, ridge size, and WAP for CENTRE gable studs?
Yes. Theoretical length + WAP gets you to the top of the ridge. Compare ridge thickness “run” to roof slope to get to top of ridge. Subtract ridge thickness to get to top point of center gable stud
If we have roof slope and OC can we find our gable stud lengths?
Yes. Create common difference by comparing roof slope to OC.
Why do we notch gable studs?
So gable rafter can sit in place and be flush for sheathing
Do ridges go up first on gable roofs?
Yes. Braced to provide starting points for fastening common rafters
Can we use a commmon rafter to EXTEND seat and plumb cuts from the ridge and BM in order to create dropped gables?
Yes
Do dropped gables have birdsmouth?
No they generally sit flat on the roof edge with only a seat cut
If my OC is 600 and my overhang is 400, how long is my lookout?
OC + overhang = 1000mm
Do lookout rest on EDGE on TOP a dropped gable
Yes
When do we lay lookouts on flat?
When they are notched into a gable instead of dropping the gable
1) two hands on material hanging off roof
3) gun towards you
Main dangers of fascia installation
Is fascia fastened to the top edge of common rafters?
No. must plane down to match roof slope
Can we use string lines to straighten fascia HORIZONTALLY?
Yes
Dwarf
Collar tie
Strut
3 ways to provide intermediate support for rafters and SHORTEN THEIR UNSUPPORTED LENGTH
Can i leave ceiling joists alone if I build dwarf walls?
No. Increase depth by AT LEAST 1” (25mm)
Are hip and common rafter roses identical?
Yes
1.414
The hip rafter run as compared to a “base 1” common rafter run
What is a pin rafter the same as?
Common rafter but used on the end of a hip roof
Do we shorten a hip rafter at the top based on the common rafter or ridge material?
COMMON RAFTER 1/2 DIAGONAL
6/12 and 6/17
Approximate slopes of equal slopes common and hip rafters
Inside = 1/2 diagonal
Outside = full diagonal
Shortenings for hips or valleys if the material is inside or outside the house
38–>27–>54
19–>13.5–>27
Horizontal, half diagonal, full diagonal thicknesses
Measuring forward and back 1/2 the material thickness and cutting bevels
Double cheek cut layout
On a hip rafter, we measure AHEAD 1/2 it’s thickness then create a new plumb line to….
Create a new seat cut that matches the WAP of common rafters and allows the hip to plane out with the commons
Why do we (not often) bevel the top edge of the hip rafter?
Alternative to dropping in order for material to plane out
1) working points
2) ridge and fascia shortenings + level cut at tail for fascia width
3) common rafter WAP measurement
4) BM dropped according to hip 1/2 thickness and WAP from 3)
5) square or cheek BM plumbs
Hip rafter layout
90deg to walls from plate to hip rafter
Hip jack
Are hip jack common differences = run?
No. CD is on a slope not horizontal
If my hip jacks are all meeting at the same point on each side of a hip, is my common RUN difference the OC?
Yes. BUT ONLY THE RUN NOT THE LINE LENGTH
OC x SGF90
Common difference for hip jacks
Common rafter LL - CD (common difference)
Adjacent hip jack LL
Do hip jacks need single cheeks?
Yes. They meet at 45deg to hip rafter
Building length - width
Hip roof ridge
Hip ridge + 1/2 common rafter thick + 1/2 common rafter thick
Ridge cutting length
Major and minor ridges meet
Equal SPAN intersecting roof
Minor ridge does not touch major ridge
unequal SPAN intersecting roof
Valley rafter = hip rafter
Equal span intersecting roof
Supporting valley = major hip rafter
Yes
Hip to plate
Hip jack
Hip to valley
Hip valley cripple jack
Supporting valley to valley
Valley cripple jack
Ridge to valley
Valley jack
Ridge to cap (5) rafters
Common
Pin
Hip
Supporting valley
Supported valley
Plan view rafter runs x SGF90 or SGF45
Valley and hip jack line lengths
Hip LL = supporting valley LL
Yes
Do we need to “back” the supporting valley BM plumb?
Yes, so the top will plane with the commons
Supported valley = minor hip
Yes
Are supported valley too shortenings done at horizontal thickness or diagonal thickness?
Horizontal. Butt into supporting rafter at 90deg
Valley jack = distance from intersection of supporting/supported
Yes
RUN of major valley jack = common run - valley jack offset from building edge
Yes
OC x SGF
LINE LENGTH Common difference
Valley cripple jack RUN = 2x distance from valley rafter intersection
Yes
Hip valley cripple jack RUN = offset from building of intersections portion
Yes
Run x SGF
Line length
Major width + minor projection + overhang
Equal span gable intersecting roof
Intersecting roof projection = ridge LL?
Yes
Unequal span gable ridge LL = projection + 1/2 minor span + overhang
Yes
Do metal connectors make trusses stronger and able to be built larger to span further?
Yes
Truss for exterior and interior slopes (vaulted ceiling)
Scissor
Truss under vertical AND horizontal deflection
Scissor
Single sloped truss
Mono
Pratt and Warren Co.
The flat truss company
Flat and sloped ceiling (combined) truss
Combination truss
Unequal slope truss
Dual slope truss
Attic livable space truss
Attic truss
Truss for hips and hip corners
Flat top
Jack truss
“Cut off” looking truss
Bobtail for two different ceiling levels
Truss for extra insulation
Raised heel
Truss built on another truss
Piggyback; for massive stuff transporting
3 trusses nailed together
Girder truss
Trusses that work down into smaller and smaller proportional triangles
Valley trusses
Do we install sheathing before valley trusses?
Yes
Can we stack shingle lifts all in one spot?
No. Must be spread out as trusses aren’t engineered for heavy live loads
1/2” between cap plate and truss webbing
12.5mm (1/2”) maximum bearing gap rule
Truss supported at ends = top chord compression and bottom chord tension?
Yes
Keep trusses flat when loading and storing?
Yes
Use bundle strapping to lift trusses?
Never
6” over 20’
Maximum bend allowed in truss when lifting flat from each end
Single point truss pick up
20’
Dual point truss pick up at 60deg straps
30’
Spreader bar lift
30-60’ truss
Strong back at mid-height on truss
60’+ truss lift
Bottom chord brace
Top chord brace
Diagonal brace
Diagonal centre web brace
Bracing for lifting pre-assembled truss sections
Building length
- building width
+ 1 common rafter thickness
Hip roof Beam cutting length
Is RAFTER span from the point where the rafter touches the wall plate (not birdsmouth) to the point where it touches the ridge board?
Yes
