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Carpentry Level 2 > H-6 Roofs > Flashcards

H-6 Roofs Flashcards

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1
Q

porpoise of ceiling joists

A
  • tie bottoms of rafters together
  • creating a stable triangle shape
  • tie supporting walls together so they don’t fall over
  • support ceiling finishes insulation and vapour barrier
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2
Q

dead loads

A

framing and roofing meterials

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3
Q

live loads

A

snow build up

- uplift from winds and lateral forces

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4
Q

tension in ceiling joists

A

dead loads and live loads are transferred to the supporting walls through rafters. this creates tension force. ceiling joist must be continuous across span of building, from rafter to rafter and must be fastened to rafter and wall plate.

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5
Q

Span

A

width of the building, common rafters run parallel to span

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6
Q

rafter span

A

horizontal distance between the points of support. used for designing the rafter, not calculating rafters length

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7
Q

Unis rise

A

the amount that a rafter rises for each unit it runs

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8
Q

unit run

A

is the base unit for calculating the rafters length and laying out the adjustments. One unit of runis equal to 12” or 1’ and 250mm

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9
Q

roof slope triangle

A

uses 12” as the base in the imperial system and 250mm in metric

example 8 in 12 roof, 8 is rise and 12 is run

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10
Q

pitch

A

is another way to describe roof slope. pitch can also describe the total rise of the building over the span of building. 6 in 12 roof slope refers to a half pitch roof

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11
Q

run

A

total horizontal distance that the rafter covers. on an equal slope roof with the ridge centered in the width of building, the run of a common rafter is half the width of the building. run of rafter is used to calculate length

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12
Q

total theory rise

A

the vertical distance that the rafter rises above the plate at the working line. the actual total rise is the vertical distance from the top of the wall plates to the top of the ridge and includes the wood above the plate and the birds mouth

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13
Q

rafters

A

are sloping roof framing members that transfer loads to the exterior walls and support the roofing material

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14
Q

roof joists

A

sloping roof framing members that cary both rood loads and ceiling finished and insulation.

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15
Q

common rafter

A

slopes up from the wall plate to the ridge. in plan view, the common rafter runs 90° to the wall plate and ridge. the roof slope triangle on blueprints refers to the common rafter

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16
Q

ridge

A

horizontal board used to align the tops of the common rafters. the ridge does not structurally support the rafters

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17
Q

a ridge beam

A

used to support and align rafters at the ridge. bearing walls or posts support the ridge beam. these supports are continuous to foundation.

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18
Q

projection

A

is the horizontal distance that the rafter extends beyond the building. overhang is measured along the length of the rafter.

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19
Q

overhang

A

the slope distance the rafter extends beyond the building. the overhang is measured along the length of the rafter

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20
Q

birds mouth

A

triangular section cut from the bottom edge of the rafter at the point where it sits on the top wall plate. this notch ensures that the rafter sits securely on the wall plate

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21
Q

seat cut

A

is the horizontal or level cut that forms the top of the birds mouth

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22
Q

plumb cut

A

is and cut on the rafter that is plumb when the rafter is installed.

  • vertical cut of birds mouth
  • ridge cut and tail cut are all plumb cuts
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23
Q

line length

A

is the calculated slope length from the centre ridge to the outside wall plate, or working point to working point. also referred to as theory length

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24
Q

working points

A

are the marks on the rafters where measurements are made and cuts laid out. working points are created by the intersections pf the theory lines of the rafters.
often the working point for one rafter is same for all of them always located along centre line

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25
Q

rafter tail

A

is the portion of the rafter that extends beyond the wall plate. this creates eaves

26
Q

ceiling joists

A

horizontal framing members that act as ties to resist outward pressure from the common rafters and support the finishes ceiling

27
Q

collar ties

A

horizontal framing members that are installed between opposing common rafters. they reduce the span of rafters

28
Q

Purlins

A

structural members at right angles to rafters. they can be installed on top of rafters between or below rafters

  • strapping on top of rafters is commonly used to support metal roofing, shakes or shingles or to create ventilation space on vaulted ceilings
29
Q

Gable studs

A

are used to frame the triangular ends of the gable roof. thy support the exterior wall Finnish. gable studs may be notched at the top and cut to fit the sloe of the roof. or butted under a top plate that supports the outriggers.

30
Q

outriggers

A

are used to frame the overhang of a gable roof . they support the cantilevered proportion of the roof assembly. the terms outrigger and lookout are interchangeable.

31
Q

Barge rafter (rake or fly rafter)

A

is the outside rafter at the gable end of the roof. the finish bargeboard is attached to the rake or fly rafter

32
Q

lookouts

A

horizontal members installed under the overhang of the roof and support the soffit. they are nailed to the sides of the rafter tails, to the rough facia and to the ledger

33
Q

eaves

A

are the bottom portion of the roof that extends beyond the exterior wall and includes the rafter tail. the facia and soffit

34
Q

wood above plate (WAP)

A

is the plumb line measurement of the wood above the birds mouth. its important to be aware of this when matching existing rafter trusses.

35
Q

ledger

A

in the eaves are horizontal members installed near the top of the wall that support the lookouts

36
Q

rough fascia

A

is installed at the ends of the rafter tails to align the rafters, support the ends of the lookouts, support the bottom edge of the room sheathing and provide backing for the finish fascia

37
Q

starting point for gable roof stystem

A

laying out and marking the top plates for the location on ceiling joists and rafters or trusses

38
Q

hand framed roof assembly

A
  1. instal ceiling joists first
  2. instal first length of ridge beam
  3. then cut one rafter and check if it fits
  4. cut second rafter check again
  5. use first as template for remaining rafters

install rafters in pairs on either side of ridge beam to keep it straight

39
Q

truss framed roof assembly.

A
  1. lay out truss placements on top plates
  2. gable and end trusses are erected and braced.
  3. string and block used to align the common trusses
  4. braces temporarily installed
  5. lockouts and fly rafters are framed, all permanent bracing is secured and the roof is sheathed or strapped.
40
Q

Layout and cutting ceiling joists

A

end of the ceiling joists rests on the exterior wall where it is joined to the rafter. rise and run of roof are laid out on framing square and triangle is cu off so that roof can be sheeted.

41
Q

good practice to…

A

align vertically. rafters directly above studs and directly above joists.

42
Q

Openings in ceilings

A

accommodate attic access hatches and chimneys. framing is similar to openings in floors

if more then one ceiling joist needs to be cut. you must consult with engineer.

43
Q

Framing square

A

main tool to calculate and lay out roof.

44
Q

calculating line length

A
  1. divide width of building in half
  2. use slope of roof to determine the units of run 5 in12 roof use a2+b2=c2 OR look at framing square
  3. multiply by the run to get line length
45
Q

calculating overhang

A
  1. take projection and divide by 12 to get units of run

2. then take number from square and multiply by the number you get from one.

46
Q

working points

A

important for laying out rafters is to mark the wokingpoints
can mark out birds mouth and overhang

47
Q

plumb lines

A

plumb lines are lines running plumb off of each working point.

48
Q

adjusting ridge

A

the cut at the ridge must be adjusted if a ridge is used. the rafter must be shortened by half the ridge thickness

if there is no ridge used then cut at the working point line

49
Q

Birds mouth

A

only building code requirement is that rafter must be supported by a minimum of 1.5”

50
Q

layout birds mouth

A

measure the plumb line at the working point where birds mouth is. draw horizontal seat cut 3” down from top of plumbline this will give you 1.5” bearing

then take framing square and hold it on the 3” down mark and make it so other end of square intersects board with unit of run

finished birds mouth should always have 90° angle

51
Q

tail cut

A

final cut on the common rafter is the tail cut. it is a plumb cut at the fascia. the plumb cut is laid out at the overhang working point. measure back thickness of facia and cut plumb cut.

52
Q

plate layout

A

typically follows the stud layout of supporting walls.

this may mean you have to have a weird cut for the first sheet of plywood.

53
Q

collar ties

A

horizontal members that reduce the span of rafters.

the ends of collar ties are cut at long tapers to match the slop of the roof.

54
Q

collar tie end cut

A

use the unit of run and unit of rise on framing square to lay out cut and run past end of the square.

normally installed 3/8 belowtop of rafter

55
Q

gable studs

A

gable studs that are spaced evenly will have a common difference in length. the difference in length is equal to the o.c spacing in inches divided by the unit of run and multiplied by the rise

example:
o.c spacing is 16” an the roof slope is 4 in 12
(16/12) x 4 =
1.333 x 4 = 5.33 or 5 and 5/16

56
Q

gable ends

A

use 2x4 to brace gable ends plumb

57
Q

truss certification

A

drawings of one truss

58
Q

panel points of truss

A

the intersection of web members creates a stable point called panel point. these keep bottom chord from sagging

59
Q

nailing trusses

A

toenailed into top plates or anchored into framing anchors

60
Q

bracingtrusses

A

temporary bracing along the tops of trusses keep them level and spaced evenly

Carpentry Level 2 (20 decks)

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