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ROOFING. BCGCA3007B. Types of Roofs. Types of Roofs. Types of Roofs. Problem No1. Problem No1. Exercise 2 – Draw in Hips & Valleys. Exercise 2. Review Principles of Roofing. Ridges are Level Rafters run at 90 to Ridge Hips & Valleys bisect all internal & external Corners - PowerPoint PPT Presentation
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ROOFING
BCGCA3007B
Types of Roofs
Types of Roofs
Types of Roofs
Problem No1
Problem No1
Exercise 2 – Draw in Hips & Valleys
Exercise 2
Review Principles of Roofing
1. Ridges are Level2. Rafters run at 90 to Ridge3. Hips & Valleys bisect all internal & external Corners4. Roof members are set out along centerlines
Common Rafter
• Main Roofing Member• Calculated same method as Gable• Spaced 450mm to 600mm for Tiled Roofs
600mm to 900mm for Sheet Roof• Cut using a Pattern Rafter
Centering Rafter LayoutRoofs are Set out by Centreline
Centring Rafters
Determine
Centering Rafter Layout
Ridge
• Used to centre Rafters• Length = Length – span + Rafter Thickness
Determine Ridge Length
Crown End Rafters
•Cut & Fitted Against Ridge•Act as Opposing Braces•Similar to Common Rafter•Half Rafter is Deducted
Crown End Rafter LayoutWhat is Crown End Centreline Length?
Crown End Rafters
Crown End Rafter LayoutWhat is the run of Centering Rafter & Crown End Rafter
Crown End Rafters
Ridge 140 x19 Rafter 90 x 45
Crown End Rafter LayoutWhat is the run of Centering Rafter & Crown End Rafter
Crown End Rafters
Hip Rafters
Centering Rafters
Ridge
Crown End Rafter LayoutWhat is the run of Centering Rafter & Crown End Rafter
Centering Rafter Run
Ridge 140 x19 Rafter 90 x 45
Crown End Rafter Run
Crown End & Centering Rafter
• Run Crown End Rafter = Half Span – Half Rafter Width
• Run Centering Rafter = Half Span – Half Ridge Width
Hip Rafter
• Runs From Corner to Intersection Crown End & Centering Rafter - Centerline
• Hips Bisect Corners• Fixing and Locating of Creepers• Distance above Birdsmouth is same as
common rafters
Hip Rafter LayoutRoofs are Set out by Centerline
Bisects Corner
Hip in Plan
Hip Rafter
Span of Hip
Hip Rafter
Hip Span
Hip Run
Hip Rafter
Hip Span
Hip Run
Hip Rafter
Hip Span
Hip Run
Hip Rafter
Hip Span
Hip Run
Corner Trimmed to allow a better fit
Hip Rafter
Centering Rafter LayoutRoofs are Set out by Centerline
Bisects Corner
Determine Centreline Span of Hip
Centreline Span of Hip (Z)
X = Half span = 2070
Z = √(x2) + (x2) = √(20702) + (20702)
Z = 2927
X = Half span = 2070
Z = Half span x √2
Z = 2927
Centreline Span of Hip (Z)
X = Half span = 2070
Z = √(x2) + (x2) = √(20702) + (20702)
Z = 2927
X = Half span = 2070
Z = Half span x √2
Z = 2927
Centreline Length of HipMathematically
• Methods– Pythagoras– Hip Centreline Length per Meter of Common
Rafter Run– Full Length Calculation
Hip by Pythagoras
Step 1 – Calculate Roof RiseRise = Tan 25 x 2070⁰
= 965mm
Pitch 25⁰
Hip by Pythagoras
Step 1 – Calculate Roof RiseRise = Tan 25 x 2070⁰
= 965mm
Pitch 25⁰
Hip Rise Must Be The Same
Hip by Pythagoras
Step 1 – Calculate Roof RiseRise = Tan 25 x 2070⁰
= 965mm
Pitch 25⁰
Hip Rise Must Be The Same
Hip Centreline Length = √(Hip Span² + Rise²)= 3082mm
What is the Hip Pitch ?
Rise 965mm
Hip by PythagorasPitch 25⁰Rise = 965mmHip CL = 3082
What is the Hip Pitch ?
Tan Pitch = 965/2927
Cos Pitch = 2927/3082
Pitch = 18.25⁰
Using TanTan Pitch = Rise/ Hip Span
Using CosCos Pitch = Hip Span/ Hip CL Length
Centreline Length of HipMathematically
• Methods– Pythagoras– Hip Centreline Length per Meter of Common
Rafter Run– Full Length Calculation
From Gable Roof Lessons
We Know That for the above Roof the Rafter Length per meter can be calculated as follows
Rafter per meter run = √(1² + 0.577²) = 1.149
Given Rise = 577 per metre
From Gable Roof Lessons
We Know That for the above Roof the Rafter Length per meter can be calculated as follows
Rafter per meter run = √(1² + 0.577²) = 1.149
Given Rise = 577 per metre
We learnt previously that for every run of the common rafter the hip run is 1.414
Given Rise = 577 per metre
We learnt previously that for every 1meter run of the common rafter the hip run is 1.414
Given Rise = 577 per metre
Using Pythagoras we determine the above triangle
Hip per meter of Common Rafter Run = √(1.414² + 0.577²) = 1.527
Given Rise = 577 per metre
Using Pythagoras we determine the above triangle
Hip per meter of Common Rafter Run = √(√2² + 0.577²)= √(2+ 0.577²)
= √(2.333) = 1.527
Given Rise = 577 per metre
Using Pythagoras we determine the above triangle
Hip per meter of Common Rafter Run = √(√2² + 0.577²)= √(2+ 0.577²)
= √(2.333) = 1.527
Therefore Halfspan = 2.070CL Hip Rafter = 2.070 x 1.527
= 3.161
Given Rise = 577 per metre
Lets extend this principle
Roof Pitch = 30⁰
Tan 30⁰ = 0.577
Pitch = 30⁰
Lets extend this principle
Roof Pitch = 30⁰
Tan 30⁰ = 0.577
This Brings Our Triangle from The Previous Example Back
Pitch = 30⁰
Using Pythagoras we determine the above triangle
Hip per meter of Common Rafter Run = √(√2² x 1 + 0.577²)= √(2+ 0.577²)
= √(2.333) = 1.527
Therefore for every meter of Common Rafter run at 30⁰The Hip Centreline Length = 1.527
Pitch = 30⁰
Calculate Hip Length per meter of Common Rafter Run
Pitch Span Hip Length per Meter Hip C.L Length30 545015 2370
22.5 1056025 600032 459045 11300
Calculate Hip Length per meter of Common Rafter Run
Pitch Span Hip Length Per m Hip Centerline Length30 5450 1528 416315 2370 1439 1706
22.5 10560 1474 778125 6000 1489 446732 4590 1546 354845 11300 1732 9786
