HIP ROOFING

HIP ROOFING

BCGCA3007B

Common Rafter

• For a detailed explanation of determining the common rafter, review the “Gable Roof Presentation”

Problem No1Lets warm your brain up

Calculate Underside of BeamsBirdsmouth 30mmRafter 140 x 45

Problem No1

Calculate Underside of Beams

Review Principles of Roofing

1. Ridges are Level2. Rafters run at 90⁰ to Wall Plate3. Hips & Valleys bisect all internal & external Corners4. Roof members are set out along centerlines

Ridges are Level

Golden Principles of Roofing


Rafters at 90° to top plate



Hips & Valleys bisect all internal & external Corners



Roof members are set out along centerlines

Types of Roofs

Types of Roofs

Types of Roofs

Exercise 2 – Draw in Hips & Valleys

Exercise 2

Hips & Valleys always Bisect Corners

Hips & Valleys always Bisect CornersThis also applies to complex roofs we will construct in Stage 3

Splay End Hip

Review Principles of Roofing


Centreline Plan Length 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

Determining Hip Roof Members

Common Rafter

• Main Roofing Member• Calculated same method as Gable• Spaced Usually at 450mm to 600mm for Tiled

Roofs & 600mm to 900mm for Sheet Roof– This is dependant on span tables found in AS

1684.2

• Cut using a Pattern Rafter

Determine Common Rafter

Determine Common Rafter

Step 1 - Solve 1m Triangle

25°

1

Rise = 1 x Tan 25° = 0.466

Rafter Length / m = 1 ÷ Cos 25° = 1.103

0.4661.103


25°

1

Rise = 1 x Tan 25° = 0.466


0.4661.103

Determine Centreline LengthRidge

Step 2 – Determine Plan LengthCentreline Length

25°

1

Plan Length= 2070

0.4661.103

2070(1/2 Span)Plan Length

Step 3 – Determine Rafter LengthCentreline Length

25°

1

Rafter Length = Plan Length x Rafter Length per metre (RL/m)

Rafter Length = 2070 x 1.103

Rafter Length = 2283

0.4661.103


2283

Step 4 – Determine Rise (If Required) Centreline Length

25°

1

Total Rise = Horizontal Travel x Rise per metre

Total Rise = 2070 x 0.466

Total Rise = 964

0.4661.103

2283

964


Determine True Length

Step 2 – Determine Plan LengthTrue Length

25°

1

Plan Length = ½ Span – ½ Ridge ThicknessPlan Length = 2070 – 9.5Plan Length = 2060.5

0.4661.103

2060.5Plan Length

Plan Length = Distance from Top Plate to Edge of Ridge

Ridge 190 x 19

½ Ridge = 9.5mm

Step 3 – Determine Rafter LengthTrue Length

25°

1


Rafter Length = 2060.5 x 1.103


0.4661.103

2060.5Plan Length

2273

Step 4 – Determine Rise (If Required) True Length

25°

1

Total Rise = Plan Length x Rise per metre

Total Rise = 2060.5 x 0.466

Total Rise = 960

0.4661.103

2283

960

2060.5Plan Length

Note – Rise is measured to pitching line only and IS NOT THE FULL HEIGHT OF THE ROOF

Centreing Rafter LayoutRoofs are Set out by Centreline

Centring Rafters

Centering Rafters Set back by Half Span

Centreing Rafter Layout




Centring Rafters are determined in the same manner as Common Rafter




Exercise – Determine Centring Rafters at 25˚




25°

1

Rise = 1 x Tan 25° = 0.466


0.4661.103

This is the Same triangle as,•Common Rafter

Determine Centreline LengthRidge


25°

1

Plan Length= 2070

0.4661.103



25°

1




0.4661.103


2283

Step 4 – Determine Rise (If Required) Centreline Length

25°

1

Total Rise = Horizontal Travel x Rise per metre

Total Rise = 2070 x 0.466

Total Rise = 964

0.4661.103

2283

964


Determine True Length

True Length of Centering Rafters

•Same as Common Rafter

•Half Ridge Thickness Deducted


25°

1

Plan Length = ½ Span – ½ Ridge ThicknessPlan Length = 2070 – 9.5Plan Length = 2060.5

0.4661.103

2060.5Plan Length

Plan Length = Distance from Top Plate to Edge of Ridge

Ridge 190 x 19

½ Ridge = 9.5mm


25°

1




0.4661.103

2060.5Plan Length

2273

Step 4 – Determine Rise (If Required) True Length

25°

1


Total Rise = 2060.5 x 0.466

Total Rise = 960

0.4661.103

2283

960

2060.5Plan Length

Note – Rise is measured to pitching line only and IS NOT THE FULL HEIGHT OF THE ROOF

Ridge Centreline Length• Used to centre Rafters• Length = Length – Number of Hip Ends x ½ Span

Confirmation of Learning

• On A3 drawing paper draw a plan view of a roof showing

1.Centring Rafters - Centreline

2.Ridge – Centreline

Example on Next Slide

Determine Ridge True Length

Determine Ridge True Length

The Ridge Extends past the centre of the centring rafter by ½ Rafter thickness


• On A3 drawing paper draw a plan view of a roof showing

1.Centring Rafters – Actual Thickness

2.Ridge – Actual Thickness

Example on Next Slide Rafter 35mm ThickRidge 19mm Thick

Crown End Rafters

•Cut & Fitted Against Ridge•Act as Opposing Braces•Similar to Common Rafter•Half Rafter is Deducted

True Length of Centering Rafters

•Same as Centreline as Common Rafter

•Half Rafter Thickness Deducted

Crown End Rafter LayoutWhat is the Crown End Rafter Centreline Plan Length?

Crown End Rafters

Crown End Rafter LayoutWhat is the Crown End Rafter Centreline Run?

Crown End Rafters

2070 ½ Span

Confirmation of Learning• On A3 drawing paper draw a plan view of a roof showing



3.Crown End Rafter - Centreline


Rafter 35mm ThickRidge 19mm Thick

Confirmation of Learning• On A3 drawing paper draw a plan view of a roof showing



3.Crown End Rafter – Actual Thickness


All Rafters 35mm ThickRidge 19mm Thick

350

250

12535

350

250

12535

Crown End Rafter LayoutWhat is the Crown End Rafter Plan Length?

Crown End Rafters

350

250

12535

Plan Length

Crown End Rafter LayoutWhat is the Crown End Rafter Plan Length?

Crown End Rafters

Plan Length = Distance from top plate to edge of member


Crown End Rafters

Determine Plan Length of Crown End Rafter Ridge 140 x19 Rafter 90 x 45

CL Span is Half span CL Span is Half span

Crown End Rafter True LayoutWhat is the PLAN Length of the Crown End Rafter

Crown End Rafter

Hip Rafters

Centering Rafters

Ridge

Plan length measuredTo edge of Centring Rafter


Crown End Rafters



Plan Length


Crown End Rafters



½ Span – ½ Rafter


Crown End Rafters



2070 – 22.5


Crown End Rafters



2047.5

Determine Crown End Rafter


25°

1

Rise = 1 x Tan 25° = 0.466


0.4661.103

This is the Same triangle as,•Common Rafter•Centring Rafter

Determine Centreline LengthCrown End Rafter

Ridge


25°

1

Plan Length= 2070

0.4661.103



25°

1




0.4661.103


2283

Determine True LengthCentring Rafter

90 x 45


25°

1

Plan Length = ½ Span – ½ Rafter ThicknessPlan Length = 2070 – 22.5.5Plan Length = 2047.5

0.4661.103

2047.5 Plan Length

Plan Length = Horizontal Distance from Top Plate to Edge of Centring Rafter

Centring Rafter

90 x 45

½ Rafter = 22.5mm

True Length

REVIEW - Crown End Rafter LayoutWhat is the run of Centring Rafter & Crown End Rafter

Centering Rafter Run

Deduct Half Ridge

Ridge 140 x19 Rafter 90 x 45

Crown End Rafter Run deduct Half Centering Rafter


25°

1




0.4661.103

2047.5Plan Length

2258

Step 4 – Determine Rise (If Required) True Rise for Crown End

25°

1


Total Rise = 2047.5 x 0.466

Total Rise = 954mm

0.4661.103

2258

954

2047.5Plan Length

Note – Rise of the Crown Rafter is lower than the Common & Centring Rafters

Detail on Next Slide

Detail Explaining Rise of Centring Rafter

• Why isn’t the “TRUE” rise of the Crown End Rafter the same as the Common Rafters

• It depends!

Crown End Rafter LayoutRidge 140 x19 Rafter 90 x 45


A

AB

B

A

Rafter Rise

4

19

45

10

22.5

10

45

22.5

As the crown end is further from the centre it must be lower

Section A-A

Section B-B

Centring Rafter

Ridge

Crown End Rafter

Crown End Rafter

Rafter Rise

4

19

45

10

22.5

As the crown end is further from the centre it must be lower

Section A-A

Section B-B

Centring Rafter

Ridge

Crown End Rafter

Crown End Rafter

If the Centring & Crown Rafter are the same thickness they should meet at this point

10

45

22.5

Crown End & Centring Rafter• Plan Length Crown End Rafter =

Half Span – Half Centring Rafter Width• Plan Length Centring Rafter =

Half Span – Half Ridge Width

Hip Rafter

• Runs From Corner to Intersection Crown End & Centering Rafter - Centerline

• Hips Bisect Corners• Support Creepers• Fixing and Locating of Creepers• Distance above Birdsmouth is same as

common rafters called “Amount Left On”

Hip Rafter LayoutRoofs are Set out by Centerline

Bisects Corner

Hip in Plan

Hip Rafter – Plan Length

Span of Hip

Hip Rafter – Plan Length

Hip Centreline Plan Length

Hip True Plan Length

Hip Rafter

Start Point for Hip

Hip Rafter

Corner Trimmed to allow a better fit

Hip Rafter

Hip Rafter LayoutRoofs are Set out by Centerline

Bisects Corner

Determine Centreline Span of Hip

Hip & Rafter Fixed Relationship

1.00

0

1.000

90°

Hip & Rafter Fixed Relationship

1.00

0

1.000

90°

Using Pythagoras Theorem

Z = √(12 + 12)

Z = √2 or 1.414

Using Similar Triangle

1.000

1.00

0

2.000

2.00

0

1 x

√2

2 x

√2

3.145

3.14

500

0

3.14

5 x

√2

Note these triangles are not to scale

45°

45°

90° 45°

45°

90° 45°

45°

90°


Express the Plan Length of the Hip as multiples of √2

½ Span Hip Length

1.000

4.563

7.896

12.546



½ Span Hip Length

1.000 1 x √2

4.563 4.563 x √2

7.896 7.896 x √2

12.546 12.546 x √2

Centreline Plan length of Hip (Z)

½ Span = 2070

Z = 2070 x √2

Z = 2927


Determine Actual the Plan Length of the Hips Below

½ Span Hip Length

1.000

4.563

7.896

12.546



½ Span Hip Length

1.000 1 x √2 = 1.414

4.563 4.563 x √2 = 6.453

7.896 7.896 x √2 = 11.167

12.546 12.546 x √2 = 17.743

Centreline Length of Hip

• Methods– Hip Centreline Length per Meter of Common

Rafter Run– Pythagoras– Scribing– Measure in Situ

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

Roof Pitch = 30° Rise = 577 per metre

Given Rise = 577 per metre

The Hip must rise to the same height

½ Span

√2

1.000

0.5

77

30°

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

Rafter per meter run = √(1 ÷ Cos 30°) = 1.149




The Hip must rise to the same height

½ Span

√21.000

0.5

77

30°

We learnt previously that for every 1meter of Plan Length of the common rafter the hips plan length is run √2 or 1.414.

√2 = √(12 + 12)

1.0001.000



1.000 √2

1.155

We can draw the triangles formed as below

We learnt previously that for every 1meter of Plan Length of the common rafter the hips plan length is run √2 or 1.414.

√2 = √(12 + 12)

30°

0.57

7



1.000 √2

1.155

We can draw the triangles formed as below

Previously demonstrated there is a fixed relationship between the Plan Length of the Common Rafter and the Plan Length of the Hip Rafter.

Plan Length of Hip = Plan Length of Common Rafter x √(2)

30°

0.57

7



1.000 √2

1.155

If the Triangle is Solved using Pythagoras Theorem

Hip Length per metre of Rafter = √(Rise2 + √(2)2) = √(0.5772 + 2) = √(0.5772 + 2)

= 1.527

30°

Hip Length per metre of Rafter0.57

7



1.000 √2

1.155

If the Triangle is Solved using Pythagoras Theorem

Therefore for every for a 30°,

• For 1m of Plan Length of the Common Rafter • the Hip Rafter Length is 1.527

The Hip Rafter will change with the Pitch

30°

1.527

0.57

7

Pitch = 30⁰

Using Pythagoras we determine the above triangle

Hip per meter of Common Rafter Run = √(1.4142+ 0.577²)= √(2+ 0.577²)

= √(2.333) = 1.527

Therefore for every meter of Common Rafter run at 30⁰The Hip Centreline Length = 1.527

1.527

Pitch = 30⁰

If the Roof is Twice the size (2x) all numbers will be multiplied by 2

1.527

1 m Triangle

3.054

2 x

1.5272.824

1.15

4

Pitch = 30⁰

If the Roof is 3600 times the size all numbers will multiplied by 3.6

1.527

1 m Triangle

5497

3600 x

36005091

2077

Using Pythagoras we determined on last slide the above triangle

Hip per meter of Common Rafter Run = √(√(2)² + 0.577²)= √(2+ 0.333²)

= √(2.333) = 1.527

Centreline Length of Hip = ½ span x Hip Length per 1 metre of Common Rafter Plan Length

Centreline Length of Hip = 2.070 x 1.527 = 3.161


IN SUMMARY

5497

3600 x

36005091

2077

1.155

1m Triangle

1.0001.414

0.57

7

5257

3600 x

36005091

2077

1.460

1m Triangle

1.0001.414

0.36

4

20°20°

When Pitch Changes Plan dimensions do not change

IN SUMMARY

5497

3600 x

36005091

2077

1.155

1m Triangle

1.414 1.000

0.57

7

5257

3600 x

36005091

2077

1.460

1m Triangle

1.0001.414

0.36

4

20°20°

When Pitch Changes Rise & Hip dimensions do change

Centreline Length of Hip = Half span x Hip Length per meter of Common Rafter

Centreline Length of Hip = 2.070 x 1.527

= 3.161

`


`

Confirmation of LearningDetermine the Following

Pitch Span Hip Length per Meter Hip C.L Length30 545015 2370

22.5 1056025 600032 459045 11300

Confirmation of LearningDetermine the Following

Pitch Span Hip Length per Meter Hip C.L Length30 5450 1.528 416315 2370 1.439 1706

22.5 10560 1.474 778125 6000 1.489 446732 4590 1.546 354845 11300 1.732 9786




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 as the rest of the roof

Hip Centreline Length = √(Hip Span² + Rise²) = √(2927² + 965²) = 3082mm

What is the Hip Pitch ?

Rise 965mm

Hip by Pythagoras

Step 1 – Calculate Plan Length of Hip

= √(20702 x 20702)= 2927

Pitch 25⁰ Rise 965mm

Hip by Pythagoras


= √(20702 x 20702)= 2927

Pitch 25⁰ Rise 965mm

Step 2 – Determine Rise= 2070 Tan 25°= 965

Hip by Pythagoras


= √(20702 x 20702)= 2927

Pitch 25⁰

Hip Rise Must Be The Same as the rest of the roof

Hip Centreline Length = √(Hip Span² + Rise²) = √(2927² + 965²) = 3082mm

What is the Hip Pitch ?

Rise 965mm

Step 2 – Determine Rise= 2070 Tan 25°= 965

1.527

Determine Pitch of Hip

1.5271.155

1.155

√2 1.000

Or √2

0.57

7

If the hip uses a large distance to get to the rise it cannot be the same pitch as the Common Rafter


Adjacent

Opposite

Pitch°

Tan (Pitch)° = Opposite ÷ Adjacent

1.527


1.5271.155

1.155

√2 1.000

Or √2

0.57

7

Tan (Pitch)° = Opposite ÷ Adjacent = √2 ÷ 0.577

= 0.408

Use your Calculators Inverse Trigonometry FunctionInv Tan-1 (0.408) = 22°

Adjacent

Opposite




Scribing

Scribing

Scribing


• Methods– Pythagoras– Hip Centreline Length per Meter of Common

Rafter Run– Scribing– Measure in Situ

In-Situ

In-Situ

In-Situ

Determine Plumb Cut Mathamatically

Revision - Determining Angles Mathematically for Common Rafter

Roof Pitch

Right Angled Triangle

This angle must be 65⁰90 – 25 = 65

This angle must be 25⁰90 – 65 = 25

Determining Plumb Cut Angles Mathematically

1. Extend Line 90⁰ From Rafter

Determining Angles Mathematically

1. Extend Line 90⁰ From Rafter2. Extend Plumb Line from

same origin at top of Rafter



same origin at top of Rafter3. Angle Formed is same as

roof pitch


1. Extend Line 90⁰ From Rafter2. Extend Plumb Line3. Angle Formed is same as

roof pitch4. Offset = Tan (pitch) x width


1. Extend Line 90⁰ From Rafter2. Extend Plumb Line3. Angle Formed is same as

roof pitch4. Offset = Tan (25⁰) x 90

= 42

Determine Cutting Length of Hip

Steps1. Determine Corresponding

Crown End Rafter Plan Length

2. Determine True Length

Calculate Hip True LengthStep 1 – Determine Plan Length of Crown End

Pitch 25⁰Centering Rafter 90 x 45

Crown End Rafter Plan Length = Half Span – ½ Rafter Thickness= 2070 – 22.5= 4047.5 or 2048

Hip runs to edge of Crown End Rafter

Determine Hip RunHip Run Plan Length is based on Crown End Rafter’s Plan Length

Calculate Hip True LengthStep 2 – Determine True Length

Pitch 30⁰Centring Rafter 90 x 45

Hip True Length = Crown End Rafter Plan Length x Hip Length per m of Rafter= 2048 x 1.527= 3.127

Hip runs to edge of Crown End Rafter

1.527

√2 1.0000.

577

30°

Alternate Method to Calculate Hip True Length

Previous Centreline Calculation of Hip

Pitch 25⁰Rise = 965mmHip CL = 3082

Centreline Plan Length of Hip = √(Half Span² + Half Span²) = √(2070² + 2070²) = 2927

Crown End Rafter LayoutRidge 140 x19 Rafter 90 x 45Hip 140 x 19

Method 1Deduction = √(22.5²+ 22.5²)

= √1012.5= 31.8 or 32

Method 2Deduction = 1.414 x 22.5

= 31.8 or 32

Determine Run of HipPitch 25⁰Rise = 965mmHip CL = 3082

Hip Run = 2927 – 32

Hip Run = 2895

32 mm Deduction

Centreline Length

Determine Run of HipPitch 25⁰Rise = 965mmHip CL = 3082

Hip Run = 2927 – 32

Hip Run = 2895

32 mm Deduction

True Length

Determine Cutting Length of Hip

1. Determine Corresponding Crown End Rafter

2. Deductions

– Centring Rafters

– Corner of Plates

Deduction for Top Plate CutRidge 140 x19 Rafter 90 x 45Hip 140 x 19

Deduction = Hip Width / 2= 19 / 2= 9.5`

Hip Plumb CutMathematically

From previous work we determined the hip as follows

Hip Pitch may be determined either

Pitch = Tan-1 954/2895 = 0.330 = 18.25⁰

Determining Plumb Cut Mathematically – Hip 140 x 19


same origin3. Angle Formed is same as

roof pitch4. Offset = Tan (18.25⁰) x 140

= 46

Markng Out Hip

1. Set Out Top Plumb Cut

Marking Out Hip

1. Set Out Top Plumb Cut2. Measure Calculated Hip Length

and place Plumb line

Marking Out Hip


and place Plumb line3. Mark same “Amount Left on”

as the Common Rafter

Common Rafter Hip Rafter

Marking Out Hip


and place Plumb line3. Mark “Amount Left on”4. Mark deduction for top plate

Marking Out Hip

Determine Hip LengthUsing Roofing Square

Use Calculator

Revise Common Rafter

1.Press Tan 25 – what does this give you2.Therefore for every 1 metre run there is 0.466m rise3.The hip rafter , Crown End Rafter & Common Rafter have the same rise

Hip has same rise as Common Rafter & Crown End Rafter

1. Therefore for every 1 metre run of Common Rafter there is 1 metre of run for the Crown End Rafter and there is 1.414 metres of run for the hip

2. For both members there is 0.466m rise3. Using the principle of similar triangles

we reduce the size of the triangle4. In this case to fit on the steel square we

need to divide by 3

1. As we reduce hip by 3 we reduce Crown End/ Common Rafter by 3 (1000 / 3 = 333)

2. There are (2048 / 333 =) 6.150 step outs for the Crown End rafter

3. There will also be 6.150 step outs for the Hip Rafter or 6 step outs + remainder( .189 x 471) 71

4. Plumb Cut Hip

Set Out Hip with Steel Square

Step 2

Using Steel Square for Hip step out six times

Step 3Using Tape measure out along a square line of Steel Square and mark Plumb Cut

Step 1 Mark Plumb Cut to Back of Birdsmouth

1

2

34

5

6

1. Eaves Allowance2. Eaves Width = 600mm3. There are (600 / 333 =)

1.802 step outs for the Eave Overhang

4. There will also be 1.802 step outs for the Hip Rafter or 1 step outs + remainder( .802 x 471) 378

5. Plumb Cut Hip

Set Out Hip with Steel Square

Eaves AllowanceEaves Width 600mm

As Overhangs are never pre-cut, we need leave enough say 2 Step Outs + Plumb Cut

Determine Hip Edge Bevel


This angle is in the Plane as the roof

Pitch 25⁰


Top Edge of Hip is not in the same plane as the Main Roof


Extend base of Hip to plane formed by Crown End Rafter

This line is Level


Plan View

Extend base of Hip to plane formed by Crown End Rafter


Plan View

New Line Formed is same length as Hip Run


Hip Centreline Length

Hip Centreline Run

Pitch 25⁰



Hip Centreline Run

Hip Edge Bevel

Pitch 25⁰



Hip Centreline Run

Hip Edge BevelEdge Bevel = Tan-1 Hip Run

Hip Length= Tan-1 2928 3082= Tan-1 0.950

= 43.53⁰

Pitch 25⁰

Review Determining Angles Mathematically

1. From Our Common Rafter Example

2. Note – Plumb Cut is not Roof Pitch

3. We require 65⁰4. To use Bevel, angle needs

to be in this position5. Therefore 90⁰ – (Required

Angle ) = Offset Angle

Edge Bevel HipMathematically

OFFSETT Angle = 90 - (Required Angle)⁰

= 90 - 43.53⁰ ⁰

= 46.47⁰

OFFSETT = Tan 46.47 x 90

= 95

Creeper Rafters

Creeper Rafters

Determine Creepers

1. Creepers Spacing Same as Common Rafter

2. Creepers usually of same material as Common Rafter

Pitch 25⁰

Determine Creepers

1. The Centreline Run of 1st Creeper is 1 Rafter Spacing less than the Centering Rafter

2. If take a view in this direction

Pitch 25⁰

Determine Creepers

1. This reduction in length can be represented by this triangle

2. As the pitch is the same as the common Rafter we can use the 1m Triangle

3. The hypotenuse = Rafter Spacing x Rafter Length per m

= 450 x 1.103 = 496mm

This is called the CREEPER SHORTENING

Pitch 25⁰

1.000

1.103

45° in Plan

Section V

iew

This is the same pitch as Common Rafter

Determine Creepers

1. All pairs of Creepers are reduced by the creeper shortening

Determine CreepersSetting Out

1. It is impractical to use centreline to measure creepers for cutting

2. Typically you would set out to the long point

3. We need to 1st determine the plan length of the Creeper at the “LONG POINT” as a distance from the top plate

Pitch 25⁰

Determining Creepers RunDetermine First Creeper Plan Length

1. Deduct Rafter Spacing

Pitch 25⁰Hip 140x19

Gets us to here

Dis

tanc

e fr

om T

op P

late

½ S

pan

– R

aft

er S

paci

ng

Determining Creepers RunDetermine First Creeper Plan Length


2. Deduct Half Hip x 1.414


We now need to get here

Determining Creepers RunDetermine First Creeper Run


2. Deduct Half Hip x √2

3. Deduction = 9.5 x √2 = 13mm



½ S

pan

– R

aft

er S

paci

ng

– (

Hip

Th

ickn

ess

x √

2)


Determine CreepersRafter 90 x 45

We now need to getto the long point

½ S

pan

– R

aft

er S

paci

ng

– (

Hip

Th

ickn

ess

x √

2) +

½ R

afte

r T

hick

ness


Pitch 25⁰Hip 140 x19Creeper 90 x 45


2. Deduct Half Hip x 1.414

3. Deduction = 9.5 x 1.414 = 13mm

4. Add ½ thickness of creeper


Pitch 25⁰Hip 140 x19Creeper 90 x 45

The Plan Length of the 1st Creeper =

Centring Rafter RunLess Rafter SpacingLess Half Hip x 1.414Plus Half Creeper Thickness

Creeper RaftersDetermine 1st Creeper

1st Creeper Rafter Plan Length =

Half Span = 2070Minus Creeper Spacing = 450Minus Half Hip x 1.414 = 13Plus Half Creeper Thickness = 22.5

1st Creeper Plan Length = 1629.5

True Length = 1629.5 x Rafter /m = 1629.5 x 1.103 = 1797

Pitch 25⁰Hip 140 x19Creeper 90 x 45Rafter Spacing 450mmCreeper Shortening 497mm

1.000

1.103

Creeper Rafters

2nd Creeper Rafter True Length =

1st Creeper True Length = 1797Less Creeper Shortening - 497

2nd Creeper Rafter True Length = 1300


Creeper Rafters

3rd Creeper Rafter True Length =

2nd Creeper True Length = 1300Less Creeper Shortening - 497

3rd Creeper Rafter True Length = 803


Creeper Rafters

4th Creeper Rafter True Length =

3rd Creeper True Length = 803Less Creeper Shortening - 497

4th Creeper Rafter True Length = 306


Creeper Rafters

4th Creeper Rafter True Length =

3rd Creeper True Length = 794Less Creeper Shortening - 497

4th Creeper Rafter True Length = 307

Note – If distance from hip to last creeper is excessive an extra creeper may be placed to support eaves– This is called a DUMMY CREEPER


Edge Bevel Creeper

When we look in plan at a roofWe do not see its true shape

In this case we see a triangle With 2 sides appearing to equalLengths of half span

Pitch 25⁰

Edge Bevel Creeper

The true shape of the hipEnd is in fact defined byHalf Span andTrue Length Rafter

Pitch 25⁰

Edge Bevel Creeper

Edge Bevel Angle

Angle = Tan-1( Half Span ) True Length Rafter

Pitch 25⁰

Edge Bevel Creeper

Edge Bevel Angle


Angle = Tan-1(2070) 2284

Angle = Tan-1(0.9063)

= 42.19⁰

Pitch 25⁰

Edge Bevel Creeper

Edge Bevel Angle


Angle = Tan-1(2070) 2284

Angle = Tan-1(0.9063)

= 42.19⁰

Pitch 25⁰

Determine Creeper Edge Bevel

Edge Bevel Angle


Angle = Tan-1(2070) 2284

Angle = Tan-1(0.9063)

= 42.19⁰

Edge Bevel CreeperMathematically

OFFSETT Angle = 90 - (Required Angle)⁰

= 90 - 42.19⁰ ⁰

= 47.81⁰

OFFSETT = Tan 47.81 x 90⁰

= 99

Determine Purlin Edge Bevel

Plan View

Purlins Intersect at 90⁰ across Hip Rafter


Plan View

Purlins Intersect at 90⁰ across Hip Rafter


Purlins are parallel to top plate


Angles are the same for all purlins on an equally pitched roof


Angles formed at Top Plate is the same as formed at Purlin


Triangle formed by Purlin, Hip & Centering Rafter

Triangle formed by Top Plate, Hip & Centering Rafter

Similar Triangles



Edge Bevel Angle

Angle = Tan-1(Rafter Centerline) Half Span

Angle = Tan-1(2284) 2070

Angle = Tan-1(1.103)

= 47.81⁰

Pitch 25⁰

Determine Purlin & Creeper Edge Bevel

Out of Same Triangle

Creeper Edge Bevel

Purlin Edge Bevel

Pitch 25⁰

Documents

HIP ROOFING