ROOFING

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