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 Pitch Angle Pitch Angle Pitch Angle
Hip Rafter per 1m of Common Rafter Plan Length ½ Span ½ Span 22.5° ½ Span Plan Lengths
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
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
Determine Set Out Points Gathering Point is ½ Span Back from edge Walls are parallel
Determine Set Out Points This will mean for our Practical Class Exercise, the Gathering Point will be ½ Rafter in from edge of the Table Frame Gathering Point is ½ Span Back from edge Walls are parallel
Drawing Octagonal Roof without Compass
Drawing An Octagonal End Roof Draw 2 Construction Lines to scale to represent the Width of The Building
Drawing An Octagonal End Roof Draw Construction Line To Represent End of Building
Drawing An Octagonal End Roof Draw Construction Line To Represent End of Building This end is not so important
Drawing An Octagonal End Roof Draw a Construction Line Mid Span to Represent the 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 & Crown End Rafters to form Minor Crown End
Drawing An Octagonal End Roof Extend Lines Perpendicular to Ridge At ½ End Length = ½ Span x 0.414
Drawing An Octagonal End Roof Extend Sides of Building by ½ End Length = ½ Span x 0.414
Drawing An Octagonal End Roof Join up external Lines
Drawing An Octagonal End Roof Draw in Hips
Draw Octagonal End With Compass
Drawing An Octagonal End Roof Draw 2 Construction Lines to scale to represent the Width of The Building
Drawing An Octagonal End Roof Draw Construction Line To Represent End of Building
Drawing An Octagonal End Roof Draw Construction Line To Represent End of Building This end is not so important
Drawing An Octagonal End Roof Draw a Construction Line Mid Span to Represent the 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 as extended “Light” Construction Lines
Drawing An Octagonal End Roof Extend Lines Perpendicular to Ridge To intersect with HIP
Drawing An Octagonal End Roof Extend sides of Building To intersect with HIP
Drawing An Octagonal End Roof Clean Up & Draw in HIPS
Drawing An Octagonal End Roof Join up external lines
Confirmation of Learning On the A3 Paper Supplied, Draw to scale and Octagonal End Roof based on 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 = 90⁰ All Angles are plan angles
Clean Up Drawing Angle Between Crown End Rafters = 45⁰ All Angles are plan angles
Clean Up Drawing Angle Between Crowns Ends & Hips = 22.5⁰ All Angles are plan angles
Angles formed by the Roof These angles are the same no matter the size of Roof as it is a Geometric Shape All Angles are plan angles
Octagonal Roof Theory If the angle between the members is constant 22.5⁰ 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 All Angles are plan angles
Octagonal Roof Theory If the angle between the members is constant 22.5⁰ We can say in all cases, no matter the size of the roof ½ End = ½ Span x 0.414 The Triangles are the same All Angles are plan angles
Octagonal Roof Theory If the angle between the members is constant 22.5⁰ We can say in all cases, no matter the size of the roof ½ End = ½ Span x 0.414 The Triangles are the same All Angles are plan angles
Octagonal Roof Theory If the angle between the members is constant 22.5⁰ We can say in all cases, no matter the size of the roof ½ End = ½ Span x 0.414 Top Plate Projection = ½ End All Angles are plan angles
Octagonal Roof Theory If the angle between the members is constant 22.5⁰ In all cases, we can say Full End = ½ Span x 0.414 x 2 All Angles are plan angles
Octagonal Roof Theory If the angle between the members is constant 22.5⁰ Also in all cases, the full end will be Full End = ½ Span x 0.828 All Angles are plan angles
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 Top Plate Projection Full Ends NOTE – These are all Centreline Measurements
3. Set Out Roof t 22.5° between Roof Members
2. Set Out Roof (a) Top Plate projection = Tan 22.5° 22.5° between Roof Members
2. Set Out Roof (b) Octagonal End = 2 x Tan 22.5° 2X
2. 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, Top Plate Projection 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
Determine Roof Members As with all previous roof We must solve the 1m triangle
Solve 1m Triangle - Example (3a) Rafter Length per plan 1m of Travel of Rafter in Plan 22.5° Rafter Length per 1m = 1 ÷ Cos 22.5° = 1.082 (This is the Rafter Multiplier)
Solve 1m Triangle - Example 3(b) Rise per plan 1m Travel of Rafter in Plan 1.082 22.5° Rise = 1 x Tan 22.5° = 0.414 (This is the Rise Multiplier)
Solve 1m Triangle - Example 3(c) Hip Rafter Plan Length per 1m Travel of Rafter in Plan 1.082 0.414 Lets have a close look at why the Plan Length of Hip is ALWAYS 1.082 for every 1m of Rafter plan length
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 The Octagonal Roof is a geometric shape No matter the size the angles are always the same These angles are always 90⁰
Plan Length Hip Rafter The Octagonal Roof is a geometric shape No matter the size the angles are always the same These angles are always 45⁰
Plan Length Hip Rafter The Octagonal Roof is a geometric shape No matter the size the angles are always the same These angles are always 22.5⁰
Plan Length Hip Rafter These relationships are constant on all properly built Octagonal Roofs These angles are always 22.5⁰
Plan Length Hip Rafter 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 Hip Rafters 1.082
Plan Length Hip Rafter Calculate Plan Length of Hip Method 2 Plan Hip Length = ½ Span ÷ cos 22.5⁰ = 1.082 per 1m of Rafter Plan Length 1.082
Plan Length Hip Rafter Calculate Plan Length of Hip Method 2 Plan Hip Length = ½ Span ÷ cos 22.5⁰ = 1.082 per 1m of Rafter Plan Length 1.082 The Hip Plan Length is Always 1.082 x ½ Span
Hip Rafter per 1m of Common Rafter Plan Length ½ Span ½ Span 22.5° ½ Span In ALL Cases Plan Length Hip =1.082 x ½ Span
Solve 1m Triangle - Example 2(c) Hip Rafter Plan Length per 1m Travel of Rafter in Plan = Tan 22.5° x 1 = 1.082 Note – This is always the case regardless of Pitch
Solve 1m Triangle - Example 2(d) Hip Rafter Length per 1m Travel of Rafter in Plan 1.082 0.414 22.5° Hip Length / m = √(0.4142 + 1.0822 ) = √(0.171 + 1.171) = 1.159 (This is the Hip Rafter Multiplier per 1m of Rafter in plan)
Solve 1m Triangle - Example 2(e) Hip Pitch = Tan-1 (Rise per metre ÷ 1 1.082 0.414 1.159 22.5° Hip Pitch = Tan-1(RISE ÷ 1.082) = Tan-1(0.414 ÷ 1.082) = Tan-1(0.383) = 20.9° say 21° Remember this is always 1082
1m Triangle Multipliers - Example Common Rafter Multiplier Hip Rafter Multiplier 1.082 0.414 1.159 22.5° 20.9° As with previous Roofs the 1m triangle will be the basis of your calculation of Roof Members
Confirmation of Learning On your worksheet Solve the 1m triangle and determine the multipliers for the Roof Pitch given to you by your trainer Trainer to Supply Roof Pitch for This Excercise
1m Triangle - Answer Click on table below to open Spread sheet Ask Learners to demonstrate the Calculations to Confirm Knowledge
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 Determine Required Height above Pitching Line Perpendicular to Rafter Total Rise
4. RISE 4(b) Total Rise Allowances Rafter = 152 Battens = 45 Custom Orb = 17 Ridge Cap = 10 Total = 224 Total Rise is a 3 Step process Determine Required Height above Pitching Line Perpendicular to Rafter Note Rafter 190 x 35 38mm Birdsmouth 152 above Pitching Line (All measurements perpendicular to Rafter) Total Rise Pitching Line
4. RISE 4(b) Total Rise Total Rise is a 3 Step process 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 Determine Required Height above Pitching Line Perpendicular to Rafter Determine Plumb Height Total Rise
4. RISE 4(b) Total Rise To determine Plumb Height We must solve the Hypotenuse Of this Triangle Total Rise is a 3 Step process Determine Required Height above Pitching Line Perpendicular to Rafter Determine Plumb Height
4. RISE 4(b) Total Rise Total Rise is a 3 Step process Determine Required Height above Pitching Line Perpendicular to Rafter Determine Plumb Height This must be a Right Angle
4. RISE 4(b) Total Rise Total Rise is a 3 Step process Determine Required Height above Pitching Line Perpendicular to Rafter Determine Plumb Height This must be a 90° - Roof Pitch
4. RISE 4(b) Total Rise Total Rise is a 3 Step process Determine Required Height above Pitching Line Perpendicular to Rafter Determine Plumb Height This also must be a 90° - Roof Pitch
4. RISE 4(b) Total Rise Total Rise is a 3 Step process Determine Required Height above Pitching Line Perpendicular to Rafter Determine Plumb Height This must equal the Roof Pitch
4. RISE 4(b) Total Rise Total Rise is a 3 Step process Determine Required Height above Pitching Line Perpendicular to Rafter 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 Determine Required Height above Pitching Line Perpendicular to Rafter 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 Determine Required Height above Pitching Line Perpendicular to Rafter Determine Plumb Height = 242 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 Determine Required Height above Pitching Line Perpendicular to Rafter Determine Plumb Height = 242 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 Span To be Supplied by Trainer Pitch To be Supplied by Trainer Timber Depth To be Supplied by Trainer Timber Depth is used to determine amount left on Determine Rise Amount Left On Plumb Height Total Rise Click on Spread sheet to determine answers
Confirmation of Learning - Answer Based on data Span To be Supplied by Trainer Pitch To be Supplied by Trainer Timber Depth To be Supplied by Trainer Timber Depth is used to determine amount left on Determine Rise Amount Left On Plumb Height Total Rise Click on Spread sheet to determine answers
(5) Major Crown End Rafter Centreline Length How far does it travel in “Plan” ?
(5) Major Crown End Rafter Centreline Length How far does it travel in “Plan” ? Side Elevation Rafter Travels to Gathering Point Plan View
(5) Major Crown End Rafter Centreline Length How far does it travel in “Plan” ?
(5) Major Crown End Rafter Centreline Length, Which Multiplier? The Rise must be the same as Common Rafter Plan Length = ½ Span
(5) Major Crown End Rafter Centreline Length, Which Multiplier? The Rise must be the same as Common Rafter The Plan Length is the same as 1. Common Rafter Plan Length = ½ Span
(5) Major Crown End Rafter Centreline Length, Which Multiplier? The Rise must be the same as Common Rafter The Plan Length is the same as 1.Common Rafter The Pitch must be the same as 1. Common Rafter Plan Length = ½ Span
(5) Major Crown End Rafter Centreline Length, Which Multiplier? The Rise must be the same as 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 Common Rafter Multiplier 1.082 0.414 1.159 22.5° 20.9°
(5) Major Crown End Rafter Centreline Length = ½ Span x Rafter Length per m How far does it travel in “Plan” ?
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
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 Establish Crown End Rafter
5. Major Crown End (i) Plumb Cut Graphically 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 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
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 Common Rafter Multiplier 1.082 0.414 1.159 22.5° 20.9° Rafter Plumb Cut Rise = 0.414 ÷ 2 = 0.207 Run = 1.000 ÷ 2 = 0.500 Rise Run
Plumb Cut – Steel Square Method 5. (ii) – Worked Example Common Rafter Multiplier 1.082 0.414 1.159 22.5° 20.9° Rafter Plumb Cut Rise = 414 ÷ 2 = 207 Run = 1000 ÷ 2 = 500 Rise = 207 Run = 500
Plumb Cut – Steel Square Method 5. (ii) Common Rafter Multiplier 1.082 0.414 1.159 22.5° 20.9° 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 Run
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
5. Major Crown End (ii) Plumb Cut Offset Method 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°
5. Major Crown End (ii) Plumb Cut Offset Method 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 1.082 0.414 1.159 22.5°
5. Major Crown End (ii) Plumb Cut Offset Method This triangle MUST BE A SIMILAR TRIANGLE to the 1m triangle formed by the Rafter 1.082 0.414 1.159 22.5° Therefore we can use the same multipliers to determine its dimensions
5. Major Crown End (ii) Plumb Cut Offset Method This triangle MUST BE A SIMILAR TRIANGLE to the 1m triangle formed by the Rafter 1.159 What is the Pitch angle of this triangle?
5. Major Crown End (ii) Plumb Cut Offset Method This triangle MUST BE A SIMILAR TRIANGLE to the 1m triangle formed by the Rafter Pitch Angle = 22.5° 1.159 What is the Plan Length?
5. Major Crown End (ii) Plumb Cut Offset Method This triangle MUST BE A SIMILAR TRIANGLE to the 1m triangle formed by the Rafter Pitch Angle = 22.5° Plan Length = 152 + 38 = 190 1.159 What is the Plan Length?
5. Major Crown End (ii) Plumb Cut Offset Method This triangle MUST BE A SIMILAR TRIANGLE to the 1m triangle formed by the Rafter Pitch Angle = 22.5° This length is Similar to The Rise 1.159 Offset = Rise Multiplier x Plan Length = 0.414 x 190 = 77mm
Worked Example - 1 Roof Pitch 22.5° Timber Depth 190 = (Tan 22.5°) x 190 = 0.414 x 190 = 79mm
5. Major Crown End (ii) Plumb Cut Offset Method There 2 Formulas to Determine the Plumb = Tan (Roof Pitch°) x Timber Depth or = Rise per m of Rafter x Timber Depth (The first formula is probably the easiest as the second formula gets complicated with hips)
Worked Example - 1 Roof Pitch 22.5° Timber Depth 190 = (Tan 22.5°) x 190 = 0.414 x 190 = 79mm
Worked Example - 2 Roof Pitch 22.5° Timber Depth 190 = 0.414 x 190 = 79mm
5. Major Crown End (ii) Plumb Cut Offset Method Pattern Rafter (90 x 45) 90
5. Major Crown End (ii) Plumb Cut Offset Method Pattern Rafter (90 x 45) Mark Square Line 90
5. Major Crown End (ii) Plumb Cut Offset Method Pattern Rafter (90 x 45) Mark Square Line 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) Mark Square Line Determine Plumb Cut Offset and Mark Out 90 x 0.414= 37mm Mark Plumb Cut Plumb Cut 90 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 The Spreadsheet will allow Timber width to be changed
6.Minor Crown End Rafters Minor Crown End Rafters join in a similar manner to a hip rafter Major Crown End Rafter Minor Crown End Rafter
(6) Minor Crown End Rafters Centreline Length How Far does it Travel in plan? Radius = ½ Span Octagonal End Based on Semi Circle
(6) Minor Crown End Rafters Centreline Length How Far does it Travel in plan? Plan Length = ½ Span Octagonal End Based on Semi Circle Major Crown is a Radius
(6) Minor Crown End Rafters Centreline Length How Far does it Travel in plan? Plan Length = ½ Span Octagonal End Based on Semi Circle Major Crown is a Radius Minor Crown also is a Radius
(6) Minor Crown End Rafters Centreline Length How Far does it Travel in plan? Plan Length = ½ Span Minor Crown End Minor Crown End Rafters travel to Gathering Point Minor Crown End Plan Length = ½ Span
(6) Minor Crown End Rafters Centreline Length Determine Centreline Length: Which Multiplier? The Rise be same as Common Rafter & Major Crown End Rafter Minor Crown End Minor Crown End Plan Length = ½ Span
(6) Minor Crown End Rafters 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 Minor Crown End Minor Crown End Plan Length = ½ Span
(6) Minor Crown End Rafters 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 The Pitch must be the same as Minor Crown End Minor Crown End Plan Length = ½ Span
(6) Minor Crown End Rafters 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 The Pitch must be the same as Minor Crown End Minor Crown End We use the Common Rafter Multiplier = Rafter Length per metre
1m Triangle Multipliers Common Rafter Multiplier 1.082 0.414 1.159 22.5° 20.9°
(6) Minor Crown End Rafters Centreline Length = Plan Length x Rafter Length per m Note - Plan Length = ½ Span (Which is the same as the Major Crown) 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
(6) Minor Crown End Rafters To Determine the True Length we must determine the reduction in length from the Centreline Length This is called the Shortening Major Crown End Rafter Minor Crown End Rafter
(6) Minor Crown End Rafters (b) Shortening There are 2 methods to determine the Shortening Mathematically Graphically Major Crown End Rafter Minor Crown End Rafter
(6) Minor Crown End Rafters (b)(i) Shortening of Crown End Rafters from Centreline Length - Mathematically Remember Centreline Plan Length = ½ Span Major Crown End Rafter Minor Crown End Rafter
(6) Minor Crown End Rafters (b)(i) Shortening of Crown End Rafters from Centreline Length - Mathematically Rafter travels to Intersection of Centring Rafter & Major Crown
(6) Minor Crown End Rafters (b)(i) Shortening of Crown End Rafters from Centreline Length - Mathematically The Rafters Plan length is reduced by √(½ Rafter2 + ½ Rafter2) We know form our previous study Of HIP ROOFS that this can be simplified to ½ Rafter x 1.414 Note 1.414 = √2 Major Crown End Rafter Shortening Minor Crown End Rafter
(6) Minor Crown End Rafters (b)(i) Shortening of Crown End Rafters from Centreline Length - Mathematically Shortening = ½ Rafter x 1.414 Note 1.414 = √2 Major Crown End Rafter Shortening Minor Crown End Rafter
(6) Minor Crown End Rafters (b)(i) Shortening of Crown End Rafters from Centreline Length - Mathematically Shortening = ½ Rafter x 1.414 Worked Example Rafter = 35mm = (35 ÷ 2) x 1.414 = 17 x 1.414 = 24mm Note 1.414 = √2 Major Crown End Rafter Shortening 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
(6) Minor Crown End Rafters (b)(i) Shortening of Crown End Rafters from Centreline Length - Mathematically Shortening = ½ Rafter x 1.414 Worked Example Rafter = 35mm = (35 ÷ 2) x 1.414 = 17 x 1.414 = 24mm Note 1.414 = √2 Major Crown End Rafter Shortening 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” Minor Crown End Rafter
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
6. Minor Crown End Rafter (b)(ii) Shortening of Crown End Rafters - Graphically Draw Centrelines MINOR CROWN END RAFTER CENTRING RAFTERS MAJOR CROWN END RAFTER Gathering Point MINOR CROWN END
6. Minor Crown End Rafter (b)(ii) Shortening of Crown End Rafters - Graphically Draw Timber Thicknesses at full size In this case all Roof Members Are 35mm thick i.e. 17.5 either side of Centreline CENTRING RAFTERS Gathering Point MAJOR CROWN END RAFTER MINOR CROWN END
6. Minor Crown End Rafter (b)(ii) Shortening of Crown End Rafters - Graphically Dimension Shortening from Centreline Note Zoomed in for Clarity CENTRING RAFTERS MINOR CROWN END RAFTER Gathering Point MAJOR CROWN END RAFTER MINOR CROWN END
6. Minor Crown End Rafter (b)(ii) Shortening of Crown End Rafters - Graphically To put this drawing into practical use you need to understand that 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 CENTRING RAFTERS MINOR CROWN END RAFTER Gathering Point MAJOR CROWN END RAFTER MINOR CROWN END
6. Minor Crown End Rafter b) ii 6. Minor Crown End Rafter b) ii. Shortening from Centreline Length - Graphically Side Elevation Select a timber of Suitable Length to use as the Minor Crown Rafter
6. Minor Crown End Rafter b) ii 6. Minor Crown End Rafter b) ii. Shortening from Centreline Length - Graphically Side Elevation Mark Out Centreline Length as determined in 6a
6. Minor Crown End Rafter b) ii 6. Minor Crown End Rafter b) ii. Shortening from Centreline Length - Graphically Side Elevation Mark Out Plumb Cuts as determined in 6c
6. Minor Crown End Rafter d) ii 6. Minor Crown End Rafter d) ii. Shortening from Centreline Length - Graphically Side Elevation Mark Lines square on Top of Rafter
6. Minor Crown End Rafter d) ii 6. Minor Crown End Rafter d) ii. Shortening from Centreline Length - Graphically You Rafter should now be marked with Centreline Length Centreline Length Isometric View
6. Minor Crown End Rafter d) ii 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 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 6. Minor Crown End Rafter ) ii. Shortening from Centreline Length - Graphically The measurements on the drawing are in the level plane. The set out must also be in the level plane Side Elevation Mark Out Plumb Cuts as determined in 6c
6. Minor Crown End Rafter d) ii 6. Minor Crown End Rafter d) ii. Shortening from Centreline Length - Graphically Side Elevation Mark Out a level line approximately ½ way down the top plumb cut
Mark Centreline Shortening Distance 6. Minor Crown End Rafter d) ii. Shortening from Centreline Length - Graphically All measurements are taken from Centreline Length Mark Centreline Shortening Distance Side Elevation Plan View Transfer plan measurements determined in 6 (b) (ii)
Mark Line using Plumb Cut Bevel 6. Minor Crown End Rafter d) ii. Shortening from Centreline Length - Graphically Mark Line using Plumb Cut Bevel Side Elevation Plan View 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 Which represents this point in PLAN Mark Line using Plumb Cut Bevel Side Elevation Plan View Transfer plan measurements determined in 6 (d) (ii)
6. Minor Crown End Rafter d) ii 6. Minor Crown End Rafter d) ii. Shortening from Centreline Length - Graphically Centreline Length Mark Line square on Top of Rafter Isometric View Mark Out Plumb Cuts as determined in 6c
6. Minor Crown End Rafter d) ii 6. Minor Crown End Rafter d) ii. Shortening from Centreline Length - Graphically Centreline Length Mark Centreline Isometric View Mark Out Plumb Cuts as determined in 6c
Mark Edge Bevel Shortening Distance 6. Minor Crown End Rafter d) ii. Shortening from Centreline Length - Graphically Mark Edge Bevel Shortening Distance 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 Mark Line using Plumb Cut Bevel 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 Which represents these points in PLAN Mark Line using Plumb Cut Bevel Transfer plan measurements determined in 6 (d) (ii)
6. Minor Crown End Rafter d) ii 6. Minor Crown End Rafter d) ii. Shortening from Centreline Length - Graphically Centreline Length Mark Lines square on Top of Rafter Centreline Shortening Isometric View
6. Minor Crown End Rafter d) ii 6. Minor Crown End Rafter d) ii. Shortening from Centreline Length - Graphically You Rafter should now be marked with Centreline Length Centreline Shortening Edge Bevel Shortening Thickness Centreline Mark Thickness Centreline Mark Isometric View
6. Minor Crown End Rafter d) ii 6. Minor Crown End Rafter d) ii. Shortening from Centreline Length - Graphically Centreline Length Plan View Isometric View
6. Minor Crown End Rafter d) ii 6. Minor Crown End Rafter d) ii. Shortening from Centreline Length - Graphically Centreline Length Centreline Shortening Plan View Isometric View
6. Minor Crown End Rafter d) ii 6. Minor Crown End Rafter d) ii. Shortening from Centreline Length - Graphically Centreline Length Centreline Shortening Edge Bevel Shortening Plan View Isometric View
6. Minor Crown End Rafter d) ii 6. Minor Crown End Rafter d) ii. Shortening from Centreline Length - Graphically Centreline Length Centreline Shortening Edge Bevel Shortening Thickness Centreline Mark Plan View Isometric View
6. Minor Crown End Rafter d) ii 6. Minor Crown End Rafter d) ii. Shortening from Centreline Length - Graphically This is the Shape of the end of the Rafter in Plan Plan View Isometric View
6. Minor Crown End Rafter d) ii 6. Minor Crown End Rafter d) ii. Shortening from Centreline Length - Graphically This is the Shape of the End of the Rafter It is based on the measurements Determined previously Plan View Isometric View
6. Minor Crown End Rafter d) ii 6. Minor Crown End Rafter d) ii. Shortening from Centreline Length - Graphically We now replicate what we see in Plan on the Actual Rafter This is the Shape of the End of the Rafter It is based on the measurements Determined previously Plan View Isometric View
6. Minor Crown End Rafter d) ii 6. Minor Crown End Rafter d) ii. Shortening from Centreline Length - Graphically Draw Lines Starting From Edge Bevel Shortening This is the Shape of the End of the Rafter It is based on the measurements Determined previously Plan View Isometric View
6. Minor Crown End Rafter d) ii 6. Minor Crown End Rafter d) ii. Shortening from Centreline Length - Graphically Draw Lines Starting From Edge Bevel Shortening to Intersection of Centreline Shortening & Thickness Centreline to This is the Shape of the End of the Rafter It is based on the measurements Determined previously Plan View Isometric View
6. Minor Crown End Rafter d) ii 6. Minor Crown End Rafter d) ii. Shortening from Centreline Length - Graphically The Rafter is then cut to This Shape The length has also been shortened And ready to be installed Plan View Mark Out Plumb Cuts as determined in 6c Isometric 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 Develop in Plan the Shortening of an Octagonal End Roof Timber Widths to be supplied by Trainer is 45mm thick Submission should be as Answer 1 On Timber Supplied Develop shortening based on a pitch of 27° & ½ Span of 300mm Timber to be supplied by Trainer
Confirmation of Learning – Answer 1 Shortening in Plan
Confirmation of Learning – Answer 2 Shortening in Elevation
(6) Minor Crown End Rafters (c) True Length Rafter travels to Intersection of Centring Rafter & Major Crown
(6) Minor Crown End Rafters (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 Major Crown End Rafter Rafter Plan Reduction Minor Crown End Rafter
(6) Minor Crown End Rafters (b) True Length = Plan Length x Rafter Length per m Note – Plan Length = (½ Span – Shortening)) or = (½ Span – (½ Rafter x 1.414))
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. Span To be Supplied by Trainer Pitch To 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. Span To be Supplied by Trainer Pitch To be Supplied by Trainer Timber Width To be Supplied by Trainer Click on Spread Sheet to check answers
(6) Minor Crown End Rafters (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 Extend Construction Lines Perpendicular to ends of Rafter
(6) Minor Crown End Rafters (c) Plumb Cut Minor Crown i. Graphically Establish False Top Plate
(6) Minor Crown End Rafters (c) Plumb Cut Minor Crown i. Graphically Establish Plan Length
(6) Minor Crown End Rafters (c) Plumb Cut Minor Crown i. Graphically Establish Rise
(6) Minor Crown End Rafters (c) Plumb Cut Minor Crown i. Graphically 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 = 45⁰
6. Minor Crown End Rafters (e) Edge Bevel Development In Plan this Angle = 45⁰ When can you use the plan angle?
6. Minor Crown End Rafters (e) Edge Bevel Development In Plan this Angle = 45⁰ When can you use the plan angle? When you use a power tool such as Drop Saw Power Saw etc
Edge Bevel Minor Crown End Rafters Plan Angle
Edge Bevel Minor Crown End Rafters Plan Angle Both Sides Must Be Equal Plan Angle = 90⁰
Edge Bevel Minor Crown End Rafters Plan Angle Both Sides Must Be Equal Plan Angle = 45⁰ Plan Angle = 90⁰ When Can You Use The Plan For the Edge Bevel ?
Edge Bevel Minor Crown End Rafters Plan Angle Both Sides Must Be Equal Plan Angle = 45⁰ Plan Angle = 90⁰ When Can You Use The Plan For the Edge Bevel ?
Minor Crown True Angle
Minor Crown True Angle
Minor Crown True Angle
Minor Crown True Angle
Minor Crown True Angle
Minor Crown True Angle
Minor Crown True Angle
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 Centreline Length Rafter What members form the triangle?
Edge Bevel Minor Crown End Rafters True Angle Centreline Length Rafter If this angle is 45⁰ What members form the triangle?
Edge Bevel Minor Crown End Rafters True Angle Centreline Length Rafter This angle must 45⁰ What members form the triangle?
Edge Bevel Minor Crown End Rafters True Angle Centreline Length Rafter Both these sides must be equal What members form the triangle?
Edge Bevel Minor Crown End Rafters True Angle Centreline Length Rafter This line runs parallel with the top Of the Rafter Which is level What members form the triangle?
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 The Octagonal Roof is a geometric shape No matter the size the angles are always the same These angles are always 90⁰
7.Plan Length Hip Rafter The Octagonal Roof is a geometric shape No matter the size the angles are always the same These angles are always 45⁰
7.Plan Length Hip Rafter The Octagonal Roof is a geometric shape No matter the size the angles are always the same These angles are always 22.5⁰
7.Plan Length Hip Rafter These relationships are constant on all properly built Octagonal Roofs These angles are always 22.5⁰
7.Plan Length Hip Rafter 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) This is a fixed relationship Regardless of pitch
7.Plan Length Hip Rafter 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) This is a fixed relationship Regardless of pitch
Worked Example 7. Plan Length of Hip Determine Plan Length of Hip Span 7600 Plan Length = ½ Span x 1.082 = (7600 ÷ 2) x 1.082 = 3800 x 1.082 = 4112
1m Triangle Multipliers Hip Rafter Multiplier 1.082 0.414 1.159 22.5° 20.9° 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 Determine how far it travels in plan Apply the multiplier
8.Centerline Length of Hip Rafter As with all Roof members to determine the length we Determine how far it travels in plan ? Apply the multiplier
1m Triangle Multipliers Hip Rafter Multiplier 1.082 0.414 1.159 22.5° 20.9° 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 Hip Rafter Multiplier 1.082 0.414 1.159 22.5° 20.9° 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 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 Determine how far it travels in plan = ½ Span Apply the multiplier
8.Centerline Length of Hip Rafter As with all Roof members to determine the length we Determine how far it travels in plan = ½ Span Apply the multiplier
1m Triangle Multipliers Hip Rafter Multiplier 1.082 0.414 1.159 22.5° 20.9° Hip Rafter Multiplier for 22.5° = 1.159
8.Centerline Length of Hip Rafter As with all Roof members to determine the length we Determine how far it travels in plan = ½ Span 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 Span 7600mm Pitch 22.5° Hip Multiplier 1.159 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 Span Supplied by Trainer Pitch Supplied by Trainer Hip Multiplier As derived from pitch
Confirmation of Learning - Answer Determine Centreline length of Hip Rafter Span Supplied by Trainer Pitch Supplied by Trainer Hip Multiplier As 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 Hip Plumb Cut 1.082 0.414 1.159 Rise 22.5° 20.9° Hip Run Reduce Hip Triangle to Steel Square
9b.Hip Plumb – Steel Square Method Hip Plumb Cut 1.082 0.414 1.159 Rise 22.5° 20.9° Hip Run Reduce Hip Triangle to Steel Square Divide by 2
9b.Hip Plumb – Steel Square Method Hip Plumb Cut 1.082 0.414 1.159 Rise 22.5° 20.9° Hip Run Reduce Hip Triangle to Steel Square Divide by 2 Rise = 207 Hip Run = 541
9b.Hip Plumb – Steel Square Method Hip Plumb Cut 1.082 0.414 1.159 207 22.5° 20.9° 541 Reduce Hip Triangle to Steel Square Divide by 2 Rise = 207 Hip Run = 541
9b.Hip Plumb – Offset Method
9b.Hip Plumb – Offset Method Common Rafter Multiplier 1.082 0.414 1.159 22.5° 20.9° 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 Determine how far it travels Apply the correct multiplier
10 True Length Hip Rafter a) Shortening We must determine how Far in the direction of the Rafter does the hip travel To determine the True Length Determine how far it travels Apply the correct multiplier
9. True Length Hip Rafter a) Shortening We must determine the Distance from ½ Span to The plan length This is called the shortening To determine the True Length Determine how far it travels Apply the correct multiplier
9. True Length Hip Rafter a) Shortening We Reduce from ½ Span ½ Ridge Thickness To determine the True Length Determine how far it travels Apply the correct multiplier
9. True Length Hip Rafter a) Shortening We Reduce from ½ Span ½ Ridge Thickness ½ Rafter x 1.414 To determine the True Length Determine how far it travels Apply the correct multiplier
9. True Length Hip Rafter a) Shortening We Reduce from ½ Span ½ Ridge Thickness ½ Rafter x 1.414 This Reduction is call the Shortening = ½ Ridge Thickness + ½ Rafter x 1.414 To determine the True Length Determine how far it travels Apply the correct multiplier
9. True Length Hip Rafter a) Shortening – Worked Example All members 35mm = ½ Ridge Thickness + (½ Rafter x 1.414) = 17.5 + (17.5 x 1.414) = 17.5 + 25 = 42.5mm To determine the True Length Determine how far it travels Apply the correct multiplier
Conformation of Learning Based on Data given to you by the Trainer Ridge Thickness Supplied by Trainer Rafter Thickness Supplied by Trainer Determine the Shortening
9. True Length Hip Rafter a (i) Edge Bevel – Graphically This Dimension measured from True Length in Plan
9. True Length Hip Rafter a (iii) Edge Bevel – Graphically Isometric Elevation
9. True Length Hip Rafter a (iii) Edge Bevel – Graphically This measurement Is at 90° to the Plumb Cut Isometric Elevation
9. True Length Hip Rafter a (iii) Edge Bevel – Graphically Develop Edge Bevel Isometric Elevation
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 Determine Plan Length = ½ Span - Shortening To determine the True Length Determine how far it travels Apply the correct multiplier
9. True Length Hip Rafter (b) True Plan Length – Worked Example Determine Plan Length = ½ Span – Shortening = 3800 – 42.5 = 3757.5 To determine the True Length Determine how far it travels Apply the correct multiplier
Confirmation of Learning Based on the previous exercise and data supplied by the Trainer Span Supplied 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 Mark Lines square on Top of Rafter Centreline Shortening Isometric View
9. True Length Hip Rafter (b) True Plan Length Determine Plan Length To determine the True Length Determine how far it travels Apply the correct multiplier
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 Apply Multiplier = Plan Length x Hip per 1m Rafter To determine the True Length Determine how far it travels Apply the correct multiplier
9. True Length Hip Rafter (b) True Length – Worked Example Apply Multiplier = Plan Length x Hip per 1m Rafter = 3757.5 x 1.159 = 4355 To determine the True Length Determine how far it travels Apply the correct multiplier
Confirmation of Learning Based on the previous exercises determine True Length Hip Rafter
Creepers Determine Creeper Shortening Determine Long Point Correction Determine 1st Creeper True Length Determine all other Creepers
Determine Shortening These 2 Triangles are similar
Determine Shortening The Ratio between the Sides must be equal
Determine Shortening Plan Shortening = ½ Span Spacing CL to End
Determine Shortening Plan Shortening = 1.000 200 0.414 200 0.414 For an Octagonal Roof These are always the same
Determine Shortening Plan Shortening = 2.414 200
Determine Shortening Plan Shortening = 2.414 x 200
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 Pitch Specified by Trainer Spacing Specified by Trainer
Creepers - Answer a) Shortening –at Confirmation of Learning Determine Creeper Shortening Pitch Specified by Trainer Spacing Specified by Trainer
Creepers Determine Creeper Shortening Determine Long Point Correction Determine 1st Creeper True Length Determine all other Creepers
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 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 Determine Creeper Shortening Determine Long Point Correction Determine 1st Creeper True Length Determine all other Creepers
Creepers (c) 1st 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 Determine Creeper Shortening Determine Long Point Correction Determine 1st Creeper True Length Determine all other Creepers
Creepers (d) Determine Creepers = Previous Creeper – Creeper Shortening = 2933 – 1175 = 1758 – 1175 = 583
Creepers (d) Determine Creepers