M. S. Martin / March 2004 / Reviewed & Combined March 2007,
Reviewed March 2010 Slide 2 Slide 3 Spec for example following copy
on blank paper Joists 150 x 38 sawn Oregon @ 600mm centres, max.
span 3.6m Trimmers 100 x 38 sawn Oregon @ 600mm centres Hanging
beam 240 x 45 hardwood, max. span of 5.4m On sketch following, draw
in joists and hanging beam to scale and indicate trimmer positions
also. Slide 4 Sketch picture below allow 100mm for wall frames (not
shown) Internal room sizes shown 4.100 3.300 8.350 5.800 Slide 5
Formula's No. of joists =width of room- 1 spacing Length of hanging
beam = length of room + 2 x wall thickness Trimmers = length of
wall 1 spacing Slide 6 Joists 8.350 1.600 = 13.916 1 = say 14 1 =
13 Order 13 @ 6.0m Slide 7 Hanging beam 4.150 +.200 = 4.350 Order 1
@ 4.5m Slide 8 Trimmers 5.800 1= 9.666 1.600 Say 10 1 = 9 Trimmers
at two ends plus internal wall 9 x 3 = 27,27 x.600 = 16.2 lin/m
Order 2 @ 6.0m, 1 @ 4.2m Slide 9 Flat roof construction Basic Roof
& Ceiling Frame text from P23 Flat roofs combine the roof and
ceiling frame in one Generally described as one with a pitch less
than 10 deg. To allow for extra loads the rafters / ceiling jiosts
are increased in sectional size Slide 10 Ceiling types Ceilings can
be either lined on the rake or rafters laid flat and use graded
battens to give fall to roof Slide 11 Variations to ceilings Slide
12 Slide 13 Slide 14 Skillion roofs P 25 Single sloping roofs Walls
at either end of roof at different heights Internal walls parralell
to end walls will be at different heights Walls at 90 deg. to end
walls will taper in height under the sloping rafters / joists Slide
15 Two ceiling designs Slide 16 Simplest method of marking With
skillion roofs the simplest thing is to scribe the rafter over the
supporting plates Slide 17 Lean to Roof construction P 26 This type
is constructed against an existing wall or other roof Simple
extensions Carports Verandahs Awnings Slide 18 Rafter / Ceiling
variations Common on carports, open exposed rafters Slide 19 Other
types Slide 20 Calculation of skillion rafters (eg) calculate the
quantity of 125 x 50 rafters required for the roof 4.2m long and
2.7m wide, rafter spacings 600mm centres, the difference in height
of plates is 900mm Length of rafter = (run of rafter) + (rise) No.
of rafters = (length of building) + 1 spacings Slide 21 Answer
length of rafter 2.7 +.900 = 7.29 +.81 = 8.1 = 2.846 lin/m Order
3.0m lengths 2.700 4.200 900 Slide 22 Number of rafters (4.200) +
1.600 = 7 + 1 = 8 Order 8 @ 3.0m rafters Slide 23 Slide 24 Name the
components (handout) Slide 25 Answers Roof Tiles Tile Battens Top
Plate Fascia Cornice Ceiling Joist Ceiling Lining Strutting Beam
Internal Wall BlockTop Plate Soffit Bearer Stud Soffit Lining
Anti-ponding Board Collar Tie Rafter Ridge Purlin Strut Hanging
Beam Purlin Strut Slide 26 Gable roof definitions Roof span: Is the
horizontal distance measured overall the wall plates Span Plate
Stud Section A-A Slide 27 Definitions Continued Span : The Plan
length of the rafter Slide 28 Rise: Is the vertical height measured
from the x y line to where the upper edge of the rafters would
intersect Slide 29 Centre Line Length : The hypotenuse in the right
angled triangle formed by the span and the rise Slide 30 Common
Rafter : Is the member fixed to the ridge with a plumb cut and
birdsmouthed over plate, extending to an eave. Slide 31 Pitch : The
amount of slope or gradient in a roof, typically expressed in
degrees 30 Slide 32 Continue on roofs Ridge Rafter Purlin Hanging
beam Ceiling joist Strut Slide 33 Set Out for Common Rafter Plumb
cut is at the top of the triangle We reduce the centre line length
of rafter by the thickness of the ridge to get our true length
Slide 34 Birdsmouth has a maximum cut out of one third the rafter
depth Level bevel is shown here at base of triangle Back of
birdsmouth, is outside of frame and if you take a vertical line up,
this is where it meets the x y line X-Y LINE Slide 35 Set Out on
Steel Square Calculate rise per / m. run Transfer to steel square
Reduced rise Reduced run Slide 36 Set out pattern rafter By either
stepping out with square, or by calculation
