Octagonal Roof. Notes to this Lesson This demonstration develops from knowledge gained from the development of Gable & Hip Roofs This PowerPoint does.

Octagonal Roof

Notes to this Lesson This demonstration develops from knowledge gained from the development of Gable & Hip Roofs This PowerPoint does not explain the development of the Basic Roof Members If you require an understanding of these you should first look at the Gable & Hip Roof presentations

Lesson Parameters To be Provided by Trainer and used in Confirmation Excercises

Critical Definition Plan Length Is the distance a roofing member travels, measured along the base of the Right Angled Triangle that it forms adjacent to the Pitch angle.

Example In its most common form Pitch Angle

Example Other Examples Pitch Angle

Confirmation of Learning Determine which side is the “Plan Length”

Confirmation of Learning - Answer Determine which side is the “Plan Length”

Confirmation of Learning What are the Plan Lengths of these triangles?

Confirmation of Learning - Answer Plan Lengths

Confirmation of Learning This Triangle

Octagonal Roof A Regular Geometric Shape

Roof Members can be Determined

Class Works On an A3 drawing sheet conduct the following drafting excercise

Walls are parallel Determine Set Out Points Gathering Point is ½ Span Back from edge

Walls are parallel Determine Set Out Points Gathering Point is ½ Span Back from edge This will mean for our Class Exercise, the Gathering Point will be ½ Rafter in from edge

Drawing An Octagonal End Roof Determine Length of Building

Drawing An Octagonal End Roof Determine Ridgeline (i.e. Centre Span)

Drawing An Octagonal End Roof Locate Centring Rafters (1/2 Span from end)

Drawing An Octagonal End Roof Find Gathering Point

Drawing An Octagonal End Roof Scribe Semi Circle with ½ Span as Radius

Drawing An Octagonal End Roof Draw in Centring Rafters

Drawing An Octagonal End Roof Draw in Major Crown End

Drawing An Octagonal End Roof Bisect Centring & Crown End Rafters to form Minor Crown End

Drawing An Octagonal End Roof Bisect Centring & all Crown End Rafters to form Hip Rafters

Drawing An Octagonal End Roof Extend Top Plate to Intersect with Hips

Drawing An Octagonal End Roof Intersect Tangent to Major Crown & Hips

Drawing An Octagonal End Roof Join all external line to complete shape

Confirmation of Learning On the A3 Paper Supplied, Draw to scale and Octagonal End Roof with the following Building Length = 7600mm Building Width = 4500mm Correctly Label all Roof Members

Answer Retain your drawing for future use and submission.

Review Geometry Angle Between Major Crown End & Centring Rafters = 90 ⁰

Clean Up Drawing Angle Between Crown End Rafters = 45 ⁰

Clean Up Drawing Angle Between Crowns Ends & Hips = 22.5 ⁰

Angles formed by the Roof These angles are the same no matter the size of Roof as it is a Geometric Shape

Octagonal Roof Theory If the angle between the members is constant 22.5 ⁰ We can say in all cases, no matter the size of the roof ½ End = ½ Span x tan 22.5⁰ = ½ Span x 0.414

If the angle between the members is constant 22.5 ⁰ We can say in all cases, no matter the size of the roof ½ End = ½ Span x 0.414 Octagonal Roof Theory

If the angle between the members is constant 22.5 ⁰ We can say in all cases, no matter the size of the roof ½ End = ½ Span x 0.414 Octagonal Roof Theory Top Plate Projection = ½ End

If the angle between the members is constant 22.5 ⁰ In all cases, we can say Full End = ½ Span x 0.414 x 2 Octagonal Roof Theory

If the angle between the members is constant 22.5 ⁰ Also in all cases, the full end will be Full End = ½ Span x 0.828 Octagonal Roof Theory

These formulas are the same no matter the size of the Roof Top Plate Projection = ½ Span x 0.414 (Also ½ End) Full End = ½ Span x 0.828 Octagonal Roof Theory Top Plate Projection Full Ends

Determine Roof Members As with all previous roof We must solve the 1m triangle

Solve 1m Triangle - Example (2a) Rafter Length per plan 1m of Travel of Rafter in Plan Rafter Length per 1m = 1 ÷ Cos 22.5° = 1.082 (This is the Rafter Multiplier) 22.5°

Solve 1m Triangle - Example 2(b) Rise per plan 1m Travel of Rafter in Plan Rise = 1 x Tan 22.5° = 0.414 (This is the Rise Multiplier) 1.082 22.5°

Solve 1m Triangle - Example 2(c) Hip Rafter Plan Length per 1m Travel of Rafter in Plan Lets have a close look at why the Plan Length of Hip is ALWAYS 1.082 for every 1m of Rafter plan length 1.082 0.414

The Octagonal Roof is a geometric shape No matter the size the angles are always the same Plan Length Hip Rafter

The Octagonal Roof is a geometric shape No matter the size the angles are always the same Plan Length Hip Rafter These angles are always 90 ⁰

The Octagonal Roof is a geometric shape No matter the size the angles are always the same Plan Length Hip Rafter These angles are always 45 ⁰

The Octagonal Roof is a geometric shape No matter the size the angles are always the same Plan Length Hip Rafter These angles are always 22.5 ⁰

These relationships are constant on all properly built Octagonal Roofs Plan Length Hip Rafter These angles are always 22.5 ⁰

Calculate Plan Length of Hip Method 1 Plan Hip Length = √((1/2 Span)² (1/2 Span x 0.414)²) = 1.082 per 1m of Rafter Plan Length Plan Length Hip Rafter Hip Rafters 1.082

Calculate Plan Length of Hip Method 2 Plan Hip Length = ½ Span ÷ cos 22.5⁰ = 1.082 per 1m of Rafter Plan Length Plan Length Hip Rafter 1.082

Calculate Plan Length of Hip Method 2 Plan Hip Length = ½ Span ÷ cos 22.5⁰ = 1.082 per 1m of Rafter Plan Length Plan Length Hip Rafter 1.082 The Hip Plan Length is Always 1.082 x ½ Span

Hip Rafter per 1m of Common Rafter Plan Length In ALL Cases Plan Length Hip = 1.082 x Rafter Length 1.082 is the PLAN Length Multiplier ½ Span 22.5°

= Tan 22.5° x 1 = 1.082 Note – This is always the case regardless of Pitch Solve 1m Triangle - Example 2(c) Hip Rafter Plan Length per 1m Travel of Rafter in Plan

Solve 1m Triangle - Example 2(d) Hip Rafter Length per 1m Travel of Rafter in Plan Hip Length / m = √(0.414 2 + 1.082 2 ) = √(0.171 + 1.171) = 1.159 (This is the Hip Rafter Multiplier) 1.082 22.5° 0.414

Solve 1m Triangle - Example 2(e) Hip Pitch = Tan -1 (Rise per metre ÷ 1.082) Hip Pitch = Tan -1 (0.414 ÷ 1.082) = Tan -1 (0.383) = 20.9°say 21° 1.082 22.5° 0.414 1.159

1m Triangle Multipliers - Example 1.082 22.5° 1.159 20.9° As with previous Roofs the 1m triangle will be the basis of your calculation of Roof Members Common Rafter Multiplier Hip Rafter Multiplier 0.414

Confirmation of Learning On your worksheet Solve the 1m triangle and determine the multipliers for the Roof Pitch given to you by your trainer To be Supplied

1m Triangle - Answer Click on table below to open Spread sheet

3. Set Out Roof t 22.5° between Roof Members

3. Set Out Roof 22.5° between Roof Members (a) Top Plate projection = Tan 22.5°

3. Set Out Roof (b) Octagonal End = 2 x Tan 22.5° 2X

3. Worked Example Based on the dimensions on the example sheet previous drafting exercise determine, Top Plate Projection ½ Span x 0.414 = 3800 x 0.414 = 931.5 Octagonal End ½ Span x 0.828 = 3800 x 0.828 = 1863

Confirmation of Learning Based on the full size dimensions given to you by your trainer determine, 1.Top Plate Projection 2.Octagonal End

Confirmation of Learning - Answer Based on the full size dimensions used in your previous drafting exercise determine, (Click on Spread Sheet Below to Check Answers) Entry only allowed in this cell Note minor discrepancies are rounding errors

4. RISE Rise is Calculated to the Pitching Line

4. Rise (a) Rise = ½ Span x Rise per metre (Note –Rise is calculated to pitching line) Rise Multiplier For every 1m of Plan Travel, the Roof Rises 0.414m

4. Rise (a) Rise = ½ Span x Rise per metre (Note –Rise is calculated to pitching line) Rise = 3800 x 0.414 = 1574 For every 1m of Plan Travel, the Roof Rises 0.414m

4. RISE Remember that rise is calculated to the pitching line

4. RISE The full height is calculated by determining Total Rise

4. RISE 4(b) Total Rise Total Rise is a 3 Step process 1.Determine Required Height above Pitching Line Perpendicular to Rafter Total Rise

Total Rise is a 3 Step process 1.Determine Required Height above Pitching Line Perpendicular to Rafter Pitching Line Allowances Rafter = 152 Battens = 45 Custom Orb = 17 Ridge Cap = 10 Total = 224 Note Rafter 190 x 35 38mm Birdsmouth 152 above Pitching Line (All measurements perpendicular to Rafter) 4. RISE 4(b) Total Rise

Total Rise is a 3 Step process 1.Determine Required Height above Pitching Line Perpendicular to Rafter Total Rise Allowances Rafter = 152 Battens = 45 Custom Orb = 17 Ridge Cap = 10 Total = 224

4. RISE 4(b) Total Rise Total Rise is a 3 Step process 1.Determine Required Height above Pitching Line Perpendicular to Rafter 2.Determine Plumb Height Total Rise

4. RISE 4(b) Total Rise Total Rise is a 3 Step process 1.Determine Required Height above Pitching Line Perpendicular to Rafter 2.Determine Plumb Height To determine Plumb Height We must solve the Hypotenuse Of this Triangle

4. RISE 4(b) Total Rise Total Rise is a 3 Step process 1.Determine Required Height above Pitching Line Perpendicular to Rafter 2.Determine Plumb Height This must be a Right Angle

4. RISE 4(b) Total Rise Total Rise is a 3 Step process 1.Determine Required Height above Pitching Line Perpendicular to Rafter 2.Determine Plumb Height This must be a 90° - Roof Pitch

4. RISE 4(b) Total Rise Total Rise is a 3 Step process 1.Determine Required Height above Pitching Line Perpendicular to Rafter 2.Determine Plumb Height This also must be a 90° - Roof Pitch

4. RISE 4(b) Total Rise Total Rise is a 3 Step process 1.Determine Required Height above Pitching Line Perpendicular to Rafter 2.Determine Plumb Height This must equal the Roof Pitch

4. RISE 4(b) Total Rise Total Rise is a 3 Step process 1.Determine Required Height above Pitching Line Perpendicular to Rafter 2.Determine Plumb Height This is a similar triangle that We used to determine the Rafter Multiplier

4. RISE 4(b) Total Rise Total Rise is a 3 Step process 1.Determine Required Height above Pitching Line Perpendicular to Rafter 2.Determine Plumb Height Plumb Height = Amount Left On x Rafter Length per metre = 224 x 1.082 = 242 To determine Hypotenuse We multiply “Amount Left on By Rafter Multiplier”

4. RISE 4(b) Total Rise Total Rise is a 3 Step process 1.Determine Required Height above Pitching Line Perpendicular to Rafter 2.Determine Plumb Height = 242 3.Add answer to Rise Rise = 1574 Plumb Height = 242 Total Rise = 1816

4. RISE 4(b) Total Rise Total Rise is a 3 Step process 1.Determine Required Height above Pitching Line Perpendicular to Rafter 2.Determine Plumb Height = 242 3.Add answer to Rise Rise = 1574 Plumb Height = 164 (152 x 1.082) Total Rise = 1738 If you wanted to find the height to Top of Rafter – you would substitute the perpendicular distance to the top of Rafter

Confirmation of Learning Based on data – SpanTo be Supplied by Trainer – PitchTo be Supplied by Trainer – Timber Depth To be Supplied by Trainer Timber Depth is used to determine amount left on Determine 1.Rise 2.Amount Left On Plumb Height 3.Total Rise Click on Spread sheet to determine answers

Confirmation of Learning - Answer Based on data – SpanTo be Supplied by Trainer – PitchTo be Supplied by Trainer – Timber Depth To be Supplied by Trainer Timber Depth is used to determine amount left on Determine 1.Rise 2.Amount Left On Plumb Height 3.Total Rise Click on Spread sheet to determine answers

(5) Major Crown End Rafter (a)Centreline Length How far does it travel in “Plan” ?

(a)Centreline Length How far does it travel in “Plan” ? (5) Major Crown End Rafter Rafter Travels to Gathering Point Plan View Side Elevation

(a)Centreline Length How far does it travel in “Plan” ? (5) Major Crown End Rafter

(a)Centreline Length, Which Multiplier? (5) Major Crown End Rafter Plan Length = ½ Span The Rise must be the same as 1.Common Rafter

(a)Centreline Length, Which Multiplier? (5) Major Crown End Rafter Plan Length = ½ Span The Rise must be the same as 1.Common Rafter The Plan Length is the same as 1. Common Rafter

(a)Centreline Length, Which Multiplier? (5) Major Crown End Rafter Plan Length = ½ Span The Rise must be the same as 1.Common Rafter The Plan Length is the same as 1.Common Rafter The Pitch must be the same as 1. Common Rafter

(a)Centreline Length, Which Multiplier? (5) Major Crown End Rafter The Rise must be the same as 1.Common Rafter The Plan Length is the same as 1.Common Rafter The Pitch must be the same as 1. Common Rafter We use the Common Rafter Multiplier = Rafter Length per metre

1m Triangle Multipliers 1.082 22.5° 0.414 1.159 20.9° Common Rafter Multiplier

(a)Centreline Length = ½ Span x Rafter Length per m How far does it travel in “Plan” ? (5) Major Crown End Rafter

Worked Example Exercise 5a Determine Major Crown End Centreline Length Span = 7600 Pitch = 22.5° Centreline Length = Plan Length x Rafter Length per m Note – Plan Length = ½ Span Centreline Length = 3800 x 1.082 = 4112

Confirmation of Learning Exercise 5a Based on data given to you by you trainer determine, Centreline Length Major Crown

Confirmation of Learning - Answer Exercise 5a Based on data given to you by you trainer determine, Centreline Length Major Crown Click on Spread Sheet to determine answers

5. Major Crown End (b) True Length How far does it Travel in Plan ?

5. Major Crown End (b) True Length How far does it Travel in Plan ? Travels to edge of Centring Rafter Major Crown End

5. Major Crown End (b) True Length How far does it Travel in Plan ?

5. Major Crown End (b) True Length= (½ Span – ½ Rafter) x Rafter Length per m

Worked Example Exercise 5b Determine Major Crown End Centreline Length Span = 7600 Pitch = 22.5° Rafter Width = 35mm (1/2 Rafter = 35 ÷ 2) True Length= Plan Length x Rafter Length per m – Note Plan Length = ½ Span – ½ Rafter True Length = (3800 – (35 ÷ 2)) x 1.082 = (3800 – 17.5) x 1.082 = 3782.5 x 1.082 = 4093

Confirmation of Learning Exercise 5a Based on data given to you by you trainer determine, True Length Major Crown End Rafter

Confirmation of Learning - Answer Exercise 5a Based on data given to you by you trainer determine, True Length Major Crown End Rafter Click on Spread Sheet to determine answers

5. Major Crown End (i) Plumb Cut Graphically

Establish False Top Plate 5. Major Crown End (i) Plumb Cut Graphically

Establish ½ Span 5. Major Crown End (i) Plumb Cut Graphically

Establish Rise 5. Major Crown End (i) Plumb Cut Graphically

Plumb Cut Establish Crown End Rafter 5. Major Crown End (i) Plumb Cut Graphically

Plumb Cut Establish Crown End Rafter Rise is Same as Common Rafter Plan Length is Same as Common Rafter 5. Major Crown End (i) Plumb Cut Graphically

Plumb Cut Establish Crown End Rafter Rise is Same as Common Rafter Plan Length is Same as Common Rafter Plumb Cut must be the same as Common Rafter 5. Major Crown End (i) Plumb Cut Graphically

Confirmation of Learning On the Drawing previously developed based on data given to you by your Trainer by the Graphical Method shown to you develop on an A3 Sheet, (Trainer should select a pitch between 15 to 35°) Plumb Cut - Major Crown End

Confirmation of Learning - Answer On the Drawing previously developed based on data given to you by your Trainer by the Graphical Method shown to you develop on an A3 Sheet, Plumb Cut - Major Crown End - Print Answer Drawing 1 on a clear sheet to compare with learners submissions will provide angles from 15 to 35°

Answer Drawing 1 – Click on Drawing to Open File

5. Major Crown End (ii) Plumb Cut – Steel Square Method

Plumb Cut – Steel Square Method 5. (ii) – Worked Example 1.082 22.5° 0.414 1.159 20.9° Common Rafter Multiplier Run Rafter Plumb Cut Rise = 0.414 ÷ 2 = 0.207 Run = 1.000 ÷ 2 = 0.500 Rise

Plumb Cut – Steel Square Method 5. (ii) – Worked Example 1.082 22.5° 0.414 1.159 20.9° Common Rafter Multiplier Run = 500 Rafter Plumb Cut Rise = 414 ÷ 2 = 207 Run = 1000 ÷ 2 = 500 Rise = 207

Plumb Cut – Steel Square Method 5. (ii) 1.082 22.5° 0.414 1.159 20.9° Common Rafter Multiplier Run Rafter Plumb Cut The Steel Square relies on principle of similar triangles If we reduce the 1m by half the angles will stay the same Rise

Confirmation of Learning Based on the Roof Pitch given to you by the Trainer, Determine the required measurements to set the Steel Square for – Plumb Cut Major Crown

Confirmation of Learning - Answer Based on the Roof Pitch given to you by the Trainer, Determine the required measurements to set the Steel Square for – Plumb Cut Major Crown – Click on Spread Sheet for Answers

Plumb Cut Offset Method

5. Major Crown End (ii) Plumb Cut Offset Method Total of Internal angles of Triangle formed by Roof = 180°

5. Major Crown End (ii) Plumb Cut Offset Method In a Right Angled Triangle one of the angles = 90°

5. Major Crown End (ii) Plumb Cut Offset Method The other 2 angles must = 90° (180° – 90° = 90°)

5. Major Crown End (ii) Plumb Cut Offset Method Therefore this angle Must = 90° - Roof Pitch

5. Major Crown End (ii) Plumb Cut Offset Method Therefore this angle = 90° - 22.5° = 67.5°

5. Major Crown End (ii) Plumb Cut Offset Method This Triangle is formed by the Roof

5. Major Crown End (ii) Plumb Cut Offset Method A SIMILAR triangle is also formed in this position

5. Major Crown End (ii) Plumb Cut Offset Method As the triangles are SIMILAR these angles must be the same

This Angle must = 90° - Roof Pitch = 67.5° 5. Major Crown End (ii) Plumb Cut Offset Method

This Angle must = 90° - Roof Pitch = 67.5°

If we mark a square line at Top of Rafter & Extend Base 5. Major Crown End (ii) Plumb Cut Offset Method

A Triangle is Formed 5. Major Crown End (ii) Plumb Cut Offset Method

This angle is the same as the Roof Pitch 5. Major Crown End (ii) Plumb Cut Offset Method

This angle must be 90° 5. Major Crown End (ii) Plumb Cut Offset Method

This angle must be 90° - Roof Pitch 5. Major Crown End (ii) Plumb Cut Offset Method

This triangle MUST BE A SIMILAR TRIANGLE to the 1m triangle formed by the Rafter 5. Major Crown End (ii) Plumb Cut Offset Method

This triangle MUST BE A SIMILAR TRIANGLE to the 1m triangle formed by the Rafter 5. Major Crown End (ii) Plumb Cut Offset Method 1.082 22.5° 0.414 1.159

This triangle MUST BE A SIMILAR TRIANGLE to the 1m triangle formed by the Rafter 5. Major Crown End (ii) Plumb Cut Offset Method 1.082 22.5° 0.414 1.159 Therefore we can use the same multipliers to determine its dimensions

This triangle MUST BE A SIMILAR TRIANGLE to the 1m triangle formed by the Rafter 5. Major Crown End (ii) Plumb Cut Offset Method 1.159 What is the Pitch angle of this triangle?

This triangle MUST BE A SIMILAR TRIANGLE to the 1m triangle formed by the Rafter 5. Major Crown End (ii) Plumb Cut Offset Method 1.159 What is the Plan Length? Pitch Angle = 22.5°

This triangle MUST BE A SIMILAR TRIANGLE to the 1m triangle formed by the Rafter 5. Major Crown End (ii) Plumb Cut Offset Method 1.159 What is the Plan Length? Pitch Angle = 22.5° Plan Length = 152 + 38 = 190

This triangle MUST BE A SIMILAR TRIANGLE to the 1m triangle formed by the Rafter 5. Major Crown End (ii) Plumb Cut Offset Method 1.159 Offset = Rise Multiplier x Plan Length = 0.414 x 190 = 77mm Pitch Angle = 22.5° This length is Similar to The Rise

Worked Example - 1 Roof Pitch 22.5° Timber Depth190 = (Tan 22.5°) x 190 = 0.414 x 190 = 79mm

There 2 Formulas to Determine the Plumb 1.= Tan (Roof Pitch°) x Timber Depth or 2.= Rise per m of Rafter x Timber Depth (The first formula is probably the easiest as the second formula gets complicated with hips) 5. Major Crown End (ii) Plumb Cut Offset Method

Worked Example - 1 Roof Pitch 22.5° Timber Depth190 = (Tan 22.5°) x 190 = 0.414 x 190 = 79mm

Worked Example - 2 Roof Pitch 22.5° Timber Depth190 = 0.414 x 190 = 79mm

Pattern Rafter (90 x 45) 90 5. Major Crown End (ii) Plumb Cut Offset Method

Pattern Rafter (90 x 45) 1.Mark Square Line 90 5. Major Crown End (ii) Plumb Cut Offset Method

Pattern Rafter (90 x 45) 1.Mark Square Line 2.Determine Plumb Cut Offset and Mark Out = 90 x Rise per 1m of Rafter in plan or 90 x (Tan 22.5°) = 90 x 0.414 = 37mm 90 37 5. Major Crown End (ii) Plumb Cut Offset Method

Pattern Rafter (90 x 45) 1.Mark Square Line 2.Determine Plumb Cut Offset and Mark Out 90 x 0.414= 37mm 3.Mark Plumb Cut 90 Plumb Cut 5. Major Crown End (ii) Plumb Cut Offset Method 37

Worked Example Based on the pitch of 25°and using a 150mm Deep Rafter determine, Plumb Cut Offset- Major Crown End = 190 x Rise per 1 metre of Rafter in plan = 0.414 x 190mm = 79mm

Worked Example - Answer

Confirmation of Learning Based on the pitch & Timber Width supplied by the Trainer determine, Plumb Cut Offset- Major Crown End On the Supplied A4 sheet demonstrate the set out of the “Plumb Cut”

Confirmation of Learning - Answer Based on the pitch & Timber Width supplied by the Trainer determine, Plumb Cut Offset- Major Crown End On the Supplied A4 sheet demonstrate the set out of the “Plumb Cut” Click on Spreadsheet below to generate Answers

Minor Crown End Rafters join in a similar manner to a hip rafter 6.Minor Crown End Rafters Major Crown End Rafter Minor Crown End Rafter

(6) Minor Crown End Rafters Radius = ½ Span Octagonal End Based on Semi Circle (a)Centreline Length How Far does it Travel in plan?

(6) Minor Crown End Rafters Plan Length = ½ Span Octagonal End Based on Semi Circle Major Crown is a Radius (a)Centreline Length How Far does it Travel in plan?

(6) Minor Crown End Rafters Plan Length = ½ Span Octagonal End Based on Semi Circle Major Crown is a Radius Minor Crown also is a Radius (a)Centreline Length How Far does it Travel in plan?

(6) Minor Crown End Rafters Plan Length = ½ Span Minor Crown End Rafters travel to Gathering Point (a)Centreline Length How Far does it Travel in plan? Plan Length = ½ Span Minor Crown End

(6) Minor Crown End Rafters Plan Length = ½ Span (a)Centreline Length Determine Centreline Length: Which Multiplier? The Rise be same as 1.Common Rafter & 2.Major Crown End Rafter Minor Crown End

(6) Minor Crown End Rafters Plan Length = ½ Span (a)Centreline Length Determine Centreline Length: Which Multiplier? The Rise be same as Common Rafter & Major Crown End Rafter The Plan Length is the same as Common Rafter & Major Crown End Rafter Minor Crown End

(6) Minor Crown End Rafters Plan Length = ½ Span (a)Centreline Length Determine Centreline Length: Which Multiplier? The Rise be same as Common Rafter & Major Crown End Rafter The Plan Length is the same as Common Rafter & Major Crown End Rafter The Pitch must be the same as Common Rafter & Major Crown End Rafter Minor Crown End

(6) Minor Crown End Rafters (a)Centreline Length Determine Centreline Length: Which Multiplier? The Rise be same as Common Rafter & Major Crown End Rafter The Plan Length is the same as Common Rafter & Major Crown End Rafter The Pitch must be the same as Common Rafter & Major Crown End Rafter Minor Crown End We use the Common Rafter Multiplier = Rafter Length per metre

1m Triangle Multipliers 1.082 22.5° 0.414 1.159 20.9° Common Rafter Multiplier

(a)Centreline Length = Plan Length x Rafter Length per m Note - Plan Length = ½ Span (Which is the same as the Major Crown) (6) Minor Crown End Rafters Plan Length = ½ Span

Worked Example Exercise 6a Determine Minor Crown End Centreline Length Span = 7600 Pitch = 22.5° Centreline Length = Plan Length x Rafter Length per m Note – Plan Length = ½ Span Centreline Length = 3800 x 1.082 = 4112

Confirmation of Learning Exercise 6a Based on data given to you by you trainer determine, True Length Minor Crown End Rafter

Confirmation of Learning - Answer Exercise 6a Based on data given to you by you trainer determine, Centreline Length Major Crown Click on Spread Sheet to determine answers

To Determine the True Length we must determine the reduction in length from the Centreline Length This is called the Shortening (6) Minor Crown End Rafters Major Crown End Rafter Minor Crown End Rafter

There are 2 methods to determine the Shortening I.Mathematically II.Graphically (6) Minor Crown End Rafters (b) Shortening Minor Crown End Rafter Major Crown End Rafter

(b)(i) Shortening of Crown End Rafters from Centreline Length - Mathematically Remember Centreline Plan Length = ½ Span (6) Minor Crown End Rafters Minor Crown End Rafter Major Crown End Rafter

(b)(i) Shortening of Crown End Rafters from Centreline Length - Mathematically (6) Minor Crown End Rafters Rafter travels to Intersection of Centring Rafter & Major Crown

(b)(i) Shortening of Crown End Rafters from Centreline Length - Mathematically The Rafters Plan length is reduced by √(½ Rafter 2 + ½ Rafter 2 ) We know form our previous study Of HIP ROOFS that this can be simplified to ½ Rafter x 1.414 (6) Minor Crown End Rafters Major Crown End Rafter Note 1.414 = √2 Minor Crown End Rafter Shortening

(b)(i) Shortening of Crown End Rafters from Centreline Length - Mathematically Shortening = ½ Rafter x 1.414 (6) Minor Crown End Rafters Major Crown End Rafter Shortening Note 1.414 = √2 Minor Crown End Rafter

(b)(i) Shortening of Crown End Rafters from Centreline Length - Mathematically Shortening = ½ Rafter x 1.414 Worked Example Rafter = 35mm Shortening = ½ Rafter x 1.414 = (35 ÷ 2) x 1.414 = 17 x 1.414 = 24mm (6) Minor Crown End Rafters Major Crown End Rafter Shortening Note 1.414 = √2 Minor Crown End Rafter

Confirmation of Learning Determine the shortening of the Rafter Width nominated by your trainer. Note – this is a mathematical exercise and the width need not be an orderable width

Confirmation of Learning - Answer Determine the shortening of the Rafter Width nominated by your trainer. Note – this is a mathematical exercise and the width need not be an orderable width. – Click On Spread sheet to generate answers

(b)(i) Shortening of Crown End Rafters from Centreline Length - Mathematically Shortening = ½ Rafter x 1.414 Worked Example Rafter = 35mm Shortening = ½ Rafter x 1.414 = (35 ÷ 2) x 1.414 = 17 x 1.414 = 24mm (6) Minor Crown End Rafters Major Crown End Rafter Shortening Note 1.414 = √2 Minor Crown End Rafter This is a relatively easy calculation if all Roof members are the same thickness If the Centring & Major Crown Rafters are different thicknesses you should consider Using the “Graphical Method”

6. Minor Crown End Rafter (b)(ii) Shortening of Crown End Rafters - Graphically You should develop an understanding of this method – It works on any Roof – It develops all bevels & shortenings – No formulas to remember only a method

Gathering Point CENTRING RAFTERS MINOR CROWN END RAFTER MINOR CROWN END MAJOR CROWN END RAFTER Draw Centrelines 6. Minor Crown End Rafter (b)(ii) Shortening of Crown End Rafters - Graphically

Gathering Point CENTRING RAFTERS MINOR CROWN END RAFTER MINOR CROWN END MAJOR CROWN END RAFTER Draw Timber Thicknesses at full size In this case all Roof Members Are 35mm thick i.e. 17.5 either side of Centreline 6. Minor Crown End Rafter (b)(ii) Shortening of Crown End Rafters - Graphically

Gathering Point CENTRING RAFTERS MINOR CROWN END RAFTER MINOR CROWN END MAJOR CROWN END RAFTER Dimension Shortening from Centreline Note Zoomed in for Clarity 6. Minor Crown End Rafter (b)(ii) Shortening of Crown End Rafters - Graphically

Gathering Point CENTRING RAFTERS MINOR CROWN END RAFTER MINOR CROWN END MAJOR CROWN END RAFTER To put this drawing into practical use you need to understand that 1.This is a TRUE representation of the actual Intersection of Roof members in PLAN If we can transfer these dimension to our Rafter we can determine the True length and All required edge bevels 6. Minor Crown End Rafter (b)(ii) Shortening of Crown End Rafters - Graphically

6. Minor Crown End Rafter b) ii. Shortening from Centreline Length - Graphically Select a timber of Suitable Length to use as the Minor Crown Rafter Side Elevation

6. Minor Crown End Rafter b) ii. Shortening from Centreline Length - Graphically Mark Out Centreline Length as determined in 6a Side Elevation

6. Minor Crown End Rafter b) ii. Shortening from Centreline Length - Graphically Mark Out Plumb Cuts as determined in 6c Side Elevation

6. Minor Crown End Rafter d) ii. Shortening from Centreline Length - Graphically Mark Lines square on Top of Rafter Side Elevation

6. Minor Crown End Rafter d) ii. Shortening from Centreline Length - Graphically Isometric View Centreline Length You Rafter should now be marked with 1.Centreline Length

6. Minor Crown End Rafter d) ii. Shortening from Centreline Length - Graphically These lines are Plumb Side Elevation

6. Minor Crown End Rafter d) ii. Shortening from Centreline Length - Graphically A line 90° to Plumb will be level Side Elevation

6. Minor Crown End Rafter ) ii. Shortening from Centreline Length - Graphically Mark Out Plumb Cuts as determined in 6c The measurements on the drawing are in the level plane. The set out must also be in the level plane Side Elevation

6. Minor Crown End Rafter d) ii. Shortening from Centreline Length - Graphically Mark Out a level line approximately ½ way down the top plumb cut Side Elevation

6. Minor Crown End Rafter d) ii. Shortening from Centreline Length - Graphically Transfer plan measurements determined in 6 (b) (ii) Mark Centreline Shortening Distance Side Elevation Plan View All measurements are taken from Centreline Length

6. Minor Crown End Rafter d) ii. Shortening from Centreline Length - Graphically Transfer plan measurements determined in 6 (d) (ii) Mark Line using Plumb Cut Bevel Side Elevation Plan View

6. Minor Crown End Rafter d) ii. Shortening from Centreline Length - Graphically Transfer plan measurements determined in 6 (d) (ii) Mark Line using Plumb Cut Bevel Which represents this point in PLAN Side Elevation Plan View

6. Minor Crown End Rafter d) ii. Shortening from Centreline Length - Graphically Mark Out Plumb Cuts as determined in 6c Isometric View Mark Line square on Top of Rafter Centreline Length

6. Minor Crown End Rafter d) ii. Shortening from Centreline Length - Graphically Mark Out Plumb Cuts as determined in 6c Isometric View Mark Centreline Centreline Length

6. Minor Crown End Rafter d) ii. Shortening from Centreline Length - Graphically Transfer plan measurements determined in 6 (d) (ii) Mark Edge Bevel Shortening Distance

6. Minor Crown End Rafter d) ii. Shortening from Centreline Length - Graphically Transfer plan measurements determined in 6 (d) (ii) Mark Line using Plumb Cut Bevel

6. Minor Crown End Rafter d) ii. Shortening from Centreline Length - Graphically Transfer plan measurements determined in 6 (d) (ii) Mark Line using Plumb Cut Bevel Which represents these points in PLAN

6. Minor Crown End Rafter d) ii. Shortening from Centreline Length - Graphically Isometric View Mark Lines square on Top of Rafter Centreline Shortening Centreline Length

6. Minor Crown End Rafter d) ii. Shortening from Centreline Length - Graphically Isometric View You Rafter should now be marked with 1.Centreline Length 2.Centreline Shortening 3.Edge Bevel Shortening 4.Thickness Centreline Mark Thickness Centreline Mark

Isometric View Plan View Centreline Length 6. Minor Crown End Rafter d) ii. Shortening from Centreline Length - Graphically

Isometric View Plan View Centreline Length Centreline Shortening

6. Minor Crown End Rafter d) ii. Shortening from Centreline Length - Graphically Isometric View Plan View Centreline Length Centreline Shortening Edge Bevel Shortening

6. Minor Crown End Rafter d) ii. Shortening from Centreline Length - Graphically Isometric View Thickness Centreline Mark Plan View Centreline Length Centreline Shortening Edge Bevel Shortening

6. Minor Crown End Rafter d) ii. Shortening from Centreline Length - Graphically Isometric View This is the Shape of the end of the Rafter in Plan Plan View

6. Minor Crown End Rafter d) ii. Shortening from Centreline Length - Graphically Isometric View This is the Shape of the End of the Rafter It is based on the measurements Determined previously Plan View

6. Minor Crown End Rafter d) ii. Shortening from Centreline Length - Graphically Isometric View This is the Shape of the End of the Rafter It is based on the measurements Determined previously Plan View We now replicate what we see in Plan on the Actual Rafter

6. Minor Crown End Rafter d) ii. Shortening from Centreline Length - Graphically Isometric View This is the Shape of the End of the Rafter It is based on the measurements Determined previously Plan View Draw Lines Starting From 1.Edge Bevel Shortening

6. Minor Crown End Rafter d) ii. Shortening from Centreline Length - Graphically Isometric View This is the Shape of the End of the Rafter It is based on the measurements Determined previously Plan View Draw Lines Starting From 1.Edge Bevel Shortening to Intersection of 2.Centreline Shortening & Thickness Centreline to

6. Minor Crown End Rafter d) ii. Shortening from Centreline Length - Graphically Isometric View The Rafter is then cut to This Shape The length has also been shortened And ready to be installed Mark Out Plumb Cuts as determined in 6c Plan View

Confirmation of Learning Develop in Plan the Shortening of an Octagonal End Roof Timber Widths to be supplied by Trainer is 45mm thick On Timber Supplied Develop required shortening based on a pitch of 27° & ½ Span of 300mm – Timber to be supplied by Trainer

Confirmation of Learning - Answers 1.Develop in Plan the Shortening of an Octagonal End Roof a)Timber Widths to be supplied by Trainer is 45mm thick Submission should be as Answer 1 2.On Timber Supplied Develop shortening based on a pitch of 27° & ½ Span of 300mm b)Timber to be supplied by Trainer

Confirmation of Learning – Answer 1 Shortening in Plan

Confirmation of Learning – Answer 2 Shortening in Elevation

(c) True Length (6) Minor Crown End Rafters Rafter travels to Intersection of Centring Rafter & Major Crown

(c) True Length How far does it travel in plan? Remember Centreline Plan Length = ½ Span True Length in Plan = ½ Span – ½ Rafter x 1.414 (6) Minor Crown End Rafters Rafter Plan Reduction Major Crown End Rafter Minor Crown End Rafter

(b) True Length = Plan Length x Rafter Length per m Note – Plan Length = (½ Span – Shortening)) or = (½ Span – (½ Rafter x 1.414)) (6) Minor Crown End Rafters

Worked Example Minor Crown True Length = – Plan Length x Rafter Length per m – Plan Length = (½ Span – ½ Rafter x 1.414) = (3800 –(35 ÷ 2) x 1.414) x 1.082 = (3800 – 17.5 x 1.414) x 1.082 = (3800 – 25) x 1.082 = 3775 x 1.082 = 4085

Confirmation of Learning Determine the True Length of the Minor Crown End Rafter based on data given to you by the Trainer. – SpanTo be Supplied by Trainer – PitchTo be Supplied by Trainer – Timber Width To be Supplied by Trainer

Confirmation of Learning - Answer Determine the True Length of the Minor Crown End Rafter based on data given to you by the Trainer. – SpanTo be Supplied by Trainer – PitchTo be Supplied by Trainer – Timber Width To be Supplied by Trainer Click on Spread Sheet to check answers

(c) Plumb Cut Minor Crown As we use the Common Rafter multiplier we can use the Common Rafter Plumb Cut The following slides demonstrate how to develop the plumb cut (6) Minor Crown End Rafters

(c) Plumb Cut Minor Crown i. Graphically (6) Minor Crown End Rafters Extend Construction Lines Perpendicular to ends of Rafter

(c) Plumb Cut Minor Crown i. Graphically (6) Minor Crown End Rafters Establish False Top Plate

(c) Plumb Cut Minor Crown i. Graphically (6) Minor Crown End Rafters Establish Plan Length

(c) Plumb Cut Minor Crown i. Graphically (6) Minor Crown End Rafters Establish Rise

(c) Plumb Cut Minor Crown i. Graphically (6) Minor Crown End Rafters Draw in Rafter Establish Plumb Cut Establish Roof Pitch

Confirmation of Learning Using your previous drafting exercise determine graphically, Plumb Cut - Minor Crown End

6. Minor Crown End Rafters (e) Edge Bevel Development In Plan this Angle = 45 ⁰

6. Minor Crown End Rafters (e) Edge Bevel Development In Plan this Angle = 45 ⁰ When can you use the plan angle?

6. Minor Crown End Rafters (e) Edge Bevel Development In Plan this Angle = 45 ⁰ When can you use the plan angle? When you use a power tool such as 1.Drop Saw 2.Power Saw etc

When can you use the “Plan” Angle Isometric Elevation

Power Saw A power saw can be adjusted to give an angled cut

Power Saw The angles are measured on this guide

Power Saw No matter what angle the saw is set to The saw blade is always at 90° to the front of the base plate

Plan View of Saw

Drop Saw Angles can set on the base plate and

Drop Saw Angles can set on the base plate and What ever this is called

Drop Saw Base Plate Angles are measured from the fence

Drop Saw Compound Angles are measured From the Base Plate

Edge Bevel Minor Crown End Rafters Plan Angle Plan Angle = 45 ⁰ Plan Angle = 90 ⁰

Edge Bevel Minor Crown End Rafters Plan Angle Plan Angle = 45 ⁰ Plan Angle = 90 ⁰ Both Sides Must Be Equal

Edge Bevel Minor Crown End Rafters Plan Angle Plan Angle = 45 ⁰ Plan Angle = 90 ⁰ Both Sides Must Be Equal When Can You Use The Plan For the Edge Bevel ?

Minor Crown True Angle

Edge Bevel Minor Crown End Rafters True Angle What members form the triangle?

Edge Bevel Minor Crown End Rafters True Angle What members form the triangle? Centreline Length Rafter

Edge Bevel Minor Crown End Rafters True Angle What members form the triangle? Centreline Length Rafter If this angle is 45 ⁰

Edge Bevel Minor Crown End Rafters True Angle What members form the triangle? Centreline Length Rafter This angle must 45 ⁰

Edge Bevel Minor Crown End Rafters True Angle What members form the triangle? Centreline Length Rafter Both these sides must be equal

Edge Bevel Minor Crown End Rafters True Angle What members form the triangle? Centreline Length Rafter This line runs parallel with the top Of the Rafter Which is level

The Octagonal Roof is a geometric shape No matter the size the angles are always the same 7.Plan Length Hip Rafter

The Octagonal Roof is a geometric shape No matter the size the angles are always the same 7. Plan Length Hip Rafter

The Octagonal Roof is a geometric shape No matter the size the angles are always the same 7.Plan Length Hip Rafter These angles are always 90 ⁰

The Octagonal Roof is a geometric shape No matter the size the angles are always the same 7.Plan Length Hip Rafter These angles are always 45 ⁰

The Octagonal Roof is a geometric shape No matter the size the angles are always the same 7.Plan Length Hip Rafter These angles are always 22.5 ⁰

These relationships are constant on all properly built Octagonal Roofs 7.Plan Length Hip Rafter These angles are always 22.5 ⁰

Calculate Plan Length of Hip Plan Hip Length = ½ Span ÷ cos 22.5⁰ = ½ Span ÷ 0.924 = 1.082 (That it is equal to the Rafter Multiplier is a coincidence in this case) 7.Plan Length Hip Rafter This is a fixed relationship Regardless of pitch

Calculate Plan Length of Hip Simple Rule Plan Hip Length = ½ Span x 1.082 (That it is equal to the Rafter Multiplier is a coincidence) 7.Plan Length Hip Rafter This is a fixed relationship Regardless of pitch

Worked Example 7. Plan Length of Hip Determine Plan Length of Hip – Span7600 Plan Length = ½ Span x 1.082 = (7600 ÷ 2) x 1.082 = 3800 x 1.082 = 4112

1m Triangle Multipliers 1.082 22.5° 0.414 1.159 20.9° Hip Rafter Multiplier When we solved the 1m Triangle we developed the Hip Multiplier

8.Centerline Length of Hip Rafter As with all Roof members to determine the length we 1.Determine how far it travels in plan 2.Apply the multiplier

8.Centerline Length of Hip Rafter As with all Roof members to determine the length we 1.Determine how far it travels in plan ? 2.Apply the multiplier

1m Triangle Multipliers 1.082 22.5° 0.414 1.159 20.9° Hip Rafter Multiplier If we remember our multiplier is derived on the following premise Hip Rafter Length for every 1m metre of Rafter in Plan

1m Triangle Multipliers 1.082 22.5° 0.414 1.159 20.9° Hip Rafter Multiplier If we remember our multiplier is derived on the following premise Hip Rafter Length for every 1m metre of Rafter in Plan It is the Plan Length of the Rafter that we must determine!

8.Centerline Length of Hip Rafter How far does the Rafter Travel in plan to intersect the Hip in plan?

8.Centerline Length of Hip Rafter How far does the Rafter Travel in plan to intersect the Hip in plan? The Rafter travels ½ Span

8.Centerline Length of Hip Rafter As with all Roof members to determine the length we 1.Determine how far it travels in plan = ½ Span 2.Apply the multiplier

1m Triangle Multipliers 1.082 22.5° 0.414 1.159 20.9° Hip Rafter Multiplier Hip Rafter Multiplier for 22.5° = 1.159

8.Centerline Length of Hip Rafter As with all Roof members to determine the length we 1.Determine how far it travels in plan = ½ Span 2.Apply the multiplier = As per 1m triangle multiplier

8.Centerline Length of Hip Rafter Centreline Length of Hip = Plan Length x Hip Rafter Length per m Note - Plan Length = ½ Span

Worked Example Determine Centreline length of Hip Rafter – Span7600mm – Pitch22.5° – Hip Multiplier1.159 Centreline Length of Hip = Plan Length x Hip Rafter Length per m Note - Plan Length = ½ Span = (7800 ÷ 2) x 1.159 = 3800 x 1.159 = 4404

Confirmation of Learning Determine Centreline length of Hip Rafter – SpanSupplied by Trainer – PitchSupplied by Trainer – Hip MultiplierAs derived from pitch

Confirmation of Learning - Answer Determine Centreline length of Hip Rafter – SpanSupplied by Trainer – PitchSupplied by Trainer – Hip MultiplierAs derived from pitch Click on Spread Sheet for Answers

9. Hip Plumb Cut

9a.Hip Plumb - Graphically Draw in False Top Plate

9a.Hip Plumb - Graphically Establish Rise of Roof By drawing in Common Rafter

9a.Hip Plumb - Graphically Draw in Ridge Line

9a.Hip Plumb - Graphically Rotate Length of Hip onto Ridge

9a.Hip Plumb - Graphically Extend this length up to false Top Plate

9a.Hip Plumb - Graphically Establish the rise The Rise will be the same as the Common Rafter Rise

9a.Hip Plumb - Graphically Draw in Hip Rafter

9a.Hip Plumb - Graphically Plumb Cut Hip Plumb Cut as Shown

Confirmation of Learning Using the A3 drawing previously developed using the method outlined Develop Plumb Cut - Graphically

Confirmation of Learning - Answer Using the A3 drawing previously developed using the method outlined Develop Plumb Cut – Graphically Click on Spread Sheet to determine Hip pitch based on Common Rafter Pitch, Using Pitching template on next slide to confirm

Answer Drawing 1 – Click on Drawing to Open File

9b.Hip Plumb – Steel Square Method Rise Hip Run Hip Plumb Cut 1.082 22.5° 0.414 1.159 20.9° Reduce Hip Triangle to Steel Square

9b.Hip Plumb – Steel Square Method Rise Hip Run Hip Plumb Cut 1.082 22.5° 0.414 1.159 20.9° Reduce Hip Triangle to Steel Square Divide by 2

9b.Hip Plumb – Steel Square Method Rise Hip Run Hip Plumb Cut 1.082 22.5° 0.414 1.159 20.9° Reduce Hip Triangle to Steel Square Divide by 2 Rise = 207 Hip Run = 541

9b.Hip Plumb – Steel Square Method 207 541 Hip Plumb Cut 1.082 22.5° 0.414 1.159 20.9° Reduce Hip Triangle to Steel Square Divide by 2 Rise = 207 Hip Run = 541

9b.Hip Plumb – Offset Method

1.082 22.5° 0.414 1.159 20.9° Common Rafter Multiplier Plumb Cut Offset = Tan(Hip Pitch°) x Timber Depth or = (Timber Depth ÷ 1.082) x Rise

Worked Example 1 Using Derived Hip Pitch Roof Pitch = 22.5 Hip Pitch= 20.9° Timber Depth = 190mm = (Tan 20.9°) x Timber Depth = 0.382 x 190 = 73mm

Worked Example 2 Using 1m Trainagle Data Roof Pitch = 22.5 Rise = 0.414 Timber Depth = 190mm = (Timber Depth ÷ 1.082) x 0.414 = (190 ÷ 1.082) x 0.414 = 175.6 x 0.414 = 73mm

10. True Length Hip Rafter To determine the True Length 1.Determine how far it travels 2.Apply the correct multiplier

10 True Length Hip Rafter a) Shortening To determine the True Length 1.Determine how far it travels 2.Apply the correct multiplier We must determine how Far in the direction of the Rafter does the hip travel

9. True Length Hip Rafter a) Shortening To determine the True Length 1.Determine how far it travels 2.Apply the correct multiplier We must determine the Distance from ½ Span to The plan length This is called the shortening

9. True Length Hip Rafter a) Shortening To determine the True Length 1.Determine how far it travels 2.Apply the correct multiplier We Reduce from ½ Span 1.½ Ridge Thickness

9. True Length Hip Rafter a) Shortening To determine the True Length 1.Determine how far it travels 2.Apply the correct multiplier We Reduce from ½ Span 1.½ Ridge Thickness 2.½ Rafter x 1.414

9. True Length Hip Rafter a) Shortening To determine the True Length 1.Determine how far it travels 2.Apply the correct multiplier We Reduce from ½ Span 1.½ Ridge Thickness 2.½ Rafter x 1.414 This Reduction is call the Shortening = ½ Ridge Thickness + ½ Rafter x 1.414

9. True Length Hip Rafter a) Shortening – Worked Example To determine the True Length 1.Determine how far it travels 2.Apply the correct multiplier All members 35mm = ½ Ridge Thickness + (½ Rafter x 1.414) = 17.5 + (17.5 x 1.414) = 17.5 + 25 = 42.5mm

Conformation of Learning Based on Data given to you by the Trainer – Ridge Thickness Supplied by Trainer – Rafter ThicknessSupplied by Trainer Determine the Shortening

9. True Length Hip Rafter a (i) Edge Bevel – Graphically This Dimension measured from True Length in Plan

Isometric Elevation 9. True Length Hip Rafter a (iii) Edge Bevel – Graphically

Isometric Elevation This measurement Is at 90° to the Plumb Cut 9. True Length Hip Rafter a (iii) Edge Bevel – Graphically

Isometric Elevation Develop Edge Bevel 9. True Length Hip Rafter a (iii) Edge Bevel – Graphically

Confirmation of Learning On Page xx develop the edge bevel graphically With Timber Supplied – Mark Plumb Cut – Mark Centreline Shortening – Mark Edge Bevels

Confirmation of Learning - Answer On Page xx develop the edge bevel graphically – Pitch – Span With Timber Supplied – Mark Centreline Length – Mark Plumb Cut – Mark Centreline Shortening – Mark Edge Bevels

9. True Length Hip Rafter (b) True Plan Length To determine the True Length 1.Determine how far it travels 2.Apply the correct multiplier Determine Plan Length = ½ Span - Shortening

9. True Length Hip Rafter (b) True Plan Length – Worked Example To determine the True Length 1.Determine how far it travels 2.Apply the correct multiplier Determine Plan Length = ½ Span – Shortening = 3800 – 42.5 = 3757.5

Confirmation of Learning Based on the previous exercise and data supplied by the Trainer – SpanSupplied by Trainer Determine True Plan Length Hip Rafter

9. True Length Hip Rafter c Develop Rafter Graphically It is possible to not bother with the maths And develop from the centreline length all measurements. This is the easiest method for complex roof

9. Minor Crown End Rafter c) Shortening from Centreline Length - Graphically Isometric View Mark Lines square on Top of Rafter Centreline Shortening Centreline Length

9. True Length Hip Rafter (b) True Plan Length To determine the True Length 1.Determine how far it travels 2.Apply the correct multiplier Determine Plan Length

Confirmation of Learning On the Supplied sheet of Paper – Draw the shortening & edge bevels for the hip – On the supplied piece of Timber based on data given to you by your trainer mark out a Hip Rafter Completely - Using Any Method

Confirmation of Learning On the Supplied sheet of Paper – Draw the shortening & edge bevels for the hip – On the supplied piece of Timber based on data given to you by your trainer mark out a Hip Rafter Completely

9. True Length Hip Rafter (b) True Length To determine the True Length 1.Determine how far it travels 2.Apply the correct multiplier Apply Multiplier = Plan Length x Hip per 1m Rafter

9. True Length Hip Rafter (b) True Length – Worked Example To determine the True Length 1.Determine how far it travels 2.Apply the correct multiplier Apply Multiplier = Plan Length x Hip per 1m Rafter = 3757.5 x 1.159 = 4355

Confirmation of Learning Based on the previous exercises determine True Length Hip Rafter

Creepers 1.Determine Creeper Shortening 2.Determine Long Point Correction 3.Determine 1 st Creeper True Length 4.Determine all other Creepers

Creepers a) Shortening Creeper Shortening = (Spacing x 2.414) x Rafter Length /m

Creepers a) Shortening – Worked Example Creeper Shortening – Pitch 22.5° – Spacing = 450mm = (Spacing x 2.414) x Rafter Length /m = (450 x 2.414) x 1.082 = 1086.3 x 1.082 = 1175

Creepers a) Shortening –at Confirmation of Learning Determine Creeper Shortening – PitchSpecified by Trainer – Spacing Specified by Trainer

Creepers - Answer a) Shortening –at Confirmation of Learning Determine Creeper Shortening – PitchSpecified by Trainer – Spacing Specified by Trainer

Creepers a) Long Point Correction in plan The simplest way is to draw it This can be done mathematically but It is a convoluted process In this the correction is -3mm

Creepers a) Long Point Correction in plan – Confirmation of Learning On an A3 Sheet Draw the intersection Of the member & Determine the Long Point Correction

Creepers - Answer a) Long Point Correction in plan – Confirmation of Learning On an A3 Sheet Draw the intersection Of the member & Determine the Long Point Correction

Creepers (c) 1 st Creeper = (½ Span + Correction) x Rafter per/m – Creeper Shortening = (3800 -3) x 1.082 – 1175 = 3797 x 1.082 – 1175 = 4108 – 1175 = 2933

Creepers 1.Determine Creeper Shortening 2.Determine Long Point Correction 3.Determine 1st Creeper True Length 4.Determine all other Creepers

Creepers (d) Determine Creepers = Previous Creeper – Creeper Shortening = 2933 – 1175 = 1758 – 1175 = 583

Creepers (d) Determine Creepers

Octagonal Roof. Notes to this Lesson This demonstration develops from knowledge gained from the development of Gable & Hip Roofs This PowerPoint does.

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Octagonal Roof. Notes to this Lesson This demonstration develops from knowledge gained from the development of Gable & Hip Roofs This PowerPoint does.

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Presentation on theme: "Octagonal Roof. Notes to this Lesson This demonstration develops from knowledge gained from the development of Gable & Hip Roofs This PowerPoint does."— Presentation transcript:

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