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Gable Roof BCGCA3007B

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Gable Roof Flush with no eaves Flush with raked eaves Boxed

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Flush Gable (No Eaves) Rafter finishes in line with end wall Barge fixed to outside wall No Overhang Studwork to take sheeting or support brickwork Not required to support roof

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Flush Gable with Raked Eaves Roof Extends to Form eave Ridge Extends to Form Eave Verge Trimmers to Support Gable Rafter Second Rafter to Support Verge Trims Trimmers to Support Verge Trims and Roof Battens Gable Stud supports 1.Second Rafter 2.Brick Work or Wall Lining Top Plate may be extended to support Rafter

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Boxed Gable Purlin & Lintel Extended to Support Verge Rafter Minimum Back span 2 x Overhang Design 3 x Overhang Verge Rafter Gable Studs & Sheeting Base of Gable Lined & Level with U/S of Eaves

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Verges Is the Junction of the Roof and the Barge/Verge Board Verge Detail for Tiled Roof

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Verge Detail for Sheet Metal Roof

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Principles of Roofing 1.Ridges are Level 2.Rafters run at 90 to wall plates 3.Hips & Valleys bisect all internal & external Corners 4.Roof members are set out along centerlines

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Roofing Members Common Rafter Ridge Collar Tie Purlin Strut Ceiling Joist Top Plate Strutting Beam Hanging Beam

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Roof Members Common Rafter – Main Sloping Roof Member Spacing 450mm or 600mm for Tiled Roofs 900mm for tiled roofs Supports Roof Battens which in turn support roof coverings Must be in single lengths or joined over supports Fixings (Nominal) 2 x 75mm Skew & 2 x 75mm into Ceiling Joist (if joist is > 38, 90mm Nails)

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Roofing Members Common Rafter Ridge Collar Tie Purlin Strut Ceiling Joist Top Plate Strutting Beam Hanging Beam

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Ridge Highest Part of the Roof Will run full length of Gable Roof Runs Parallel to TOP PLATE Fixes Rafters at Top of Roof Rafters are nailed either side and not offset by more than 1 thickness In Uncoupled Roof, they act as beams Nailed to Rafters with 2 x 75mm Nails

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Joining Ridge Boards

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Roofing Members Common Rafter Ridge Collar Tie Purlin Strut Ceiling Joist Top Plate Strutting Beam Hanging Beam

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Purlin Also known as Underpurlin Fixed to Underside of RAFTER Runs parallel to ridge and wall plates Reduce span of RAFTER Will run full length of Gable Roof

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Roofing Members Common Rafter Ridge Collar Tie Purlin Strut Ceiling Joist Top Plate Strutting Beam Hanging Beam

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Struts Transfer Loads From Purlins to Load Bearing Walls

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Also Known as Barrap Straps

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Roofing Members Common Rafter Ridge Collar Tie Purlin Strut Ceiling Joist Top Plate Strutting Beam Hanging Beam

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Collar Ties

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Gable Roof Common Rafter

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Main Roofing Member Calculated same method as Gable Spaced Usually at 450mm to 600mm for Tiled Roofs & 600mm to 900mm for Sheet Roof Cut using a Pattern Rafter

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Gable Roof Common Rafter Top Plate

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Top Part of the Wall Frame Takes structural load from Roof and Transfers it to the wall studs Size must be determined from span tables

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Pitching Line

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Starts at top corner of Top Plate Pitching Line

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Starts at top corner of Top Plate Pitching Line

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Starts at top corner of Top Plate Pitching Line Pitching line Runs Parallel to top of Rafter

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Pitching Line Starts at top corner of Top Plate Pitching Line Pitching line Runs Parallel to top of Rafter This establishes the Pitch of the Roof

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Pitching Line Starts at top corner of Top Plate Pitching Line If the pitching line went from top plate to top of roof the pitch is not correct or relevant. As you will see later it would make our calculations far harder

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Common Rafter Principles Span – From Birdsmouth to Birdsmouth Half Span – From Birdsmouth to Centre

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Common Rafter Principles Rise – Vertical height from top plate to intersections of pitching lines at Apex Rise is NOT measured to top of Rafter

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Common Rafter Principles If Rise is taken from Top Plate to Apex pitch will be incorrect

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Common Rafter Principles Measured to edge of Ridge Measured to centre of Ridge

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Confirmation of Learning Mark on Drawing in Workbook where, Centreline Length is measured to

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Centreline Length Centre Line Length

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Confirmation of Learning Centre Line Length Mark on Drawing in Workbook where, True Length is measured to

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Common Rafter Principles True Length Centre Line Length True Length is usually what we need

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Confirmation Of Learning Mark on Drawing in Workbook where, Rafter is measured from at Base

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Measurement of Rafter Mark on Drawing in Workbook where, Rafter is measured from at Base Rafter is measured from this point

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Confirmation Of Learning Mark on Drawing in Workbook where, The Rafter Length is measured

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Measurement of Rafter Mark on Drawing in Workbook where, The Rafter Length is measured The Rafter Length is measure along the pitching line

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Measurement of Rafter Mark on Drawing in Workbook where, The Rafter Length is measured You may also measure on any line that is parallel to the pitching line so long as it is between Plumb lines that pass thru the required points.

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Determine Rafter Length Mathematically Rafter 90 x 45 Ridge 125 x 19 For every roof you must solve the 1m triangle based on the roof pitch

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The “1 Metre Triangle”

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Step 1 - Solve 1m Triangle 25° This is the a triangle based on the roof pitch Plan Length of 1 metre Rise per 1 metre of Plan Length Rafter Length per 1 metre of Plan length

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Step 1 - Solve 1m Triangle 25° This is always no matter what the Roof Pitch is Plan Length of 1 metre Rise per 1 metre of Plan Length Rafter Length per 1 metre of Plan length

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Step 1 - Solve 1m Triangle 25° These dimension will always change and are dependant on the Roof Pitch. These figures will need to be determined by you. Plan Length of 1 metre Rise per 1 metre of Plan Length Rafter Length per 1 metre of Plan length

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Step 1 - Solve 1m Triangle 25° Unknown Solve all Unknown Sides of the a triangle based on the roof pitch Horizontal Travel = “Plan Length” Unknown

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Step 1 - Solve 1m Triangle 25° Rise = Plan Length x Tan (Pitch)° = x Tan 25° = Horizontal Travel = “Plan Length” Unknown Solve all Unknown Sides of the a triangle based on the roof pitch

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Step 1 - Solve 1m Triangle 25° Rafter Length / m= Plan Length ÷ Cos (Pitch)° = ÷ Cos 25° = ÷ = Rise = 1 x Tan 25° = Horizontal Travel = “Plan Length” Solve all Unknown Sides of the a triangle based on the roof pitch

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Step 1 - Solved 1m Triangle 25° Horizontal Travel = “Plan Length” For any roof of 25° the Rise per 1 m of Plan Length For any roof of 25° the Rafter Length per 1 m of Plan Length

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Confirmation of Learning Determine the following 1 metre triangles 16°20° 30° 45°

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Confirmation of Learning Determine the following 1 metre triangles 16°20° 30° 45°

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Determine Centreline Length Ridge Centreline Length is to the Centre of the Roof ½ Span

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Definition – Plan Length “Plan Length” is the Horizontal (Level) Distance a Roofing Member Travels 25° 3310 A Rafter is 3310 and is pitched at 25° Plan Length

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Definition – Plan Length Plan Length is the Horizontal (Level) Distance a Roofing Member Travels ° 3310 The Horizontal Distance that the Rafter Travels is its “PLAN LENGTH In this case is 3000

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Definition – Plan Length Plan Length is the Horizontal (Level) Distance a Roofing Member Travels ° 3310 It is important when determining any Rafter Hip Creeper Valley etc., To first determine its plan length

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Confirmation Of Learning What is the “Plan Length” of this Rafter?

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Confirmation Of Learning What is the “Plan Length” of this Rafter? This is the plan length

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Centreline Length Rafter 90 x 45 Ridge 125 x 19 What is the plan length we need to use to determine the Centreline Length of the common rafter below ?

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Centreline Length Rafter 90 x 45 Ridge 125 x 19 What is the plan length we need to use to determine the Centreline Length of the common rafter below ?

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Step 2 – Determine Plan Length Centreline Length 25° (1/2 Span) Plan Length “Plan Length” = ½ Span = 1350 Determine how far the rafter travels HORIZONTALLY PLAN LENGTH

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Step 2 – Determine Plan Length Centreline Length 25° 1 Plan Length= (1/2 Span) Plan Length “Plan Length” = ½ Span = 1350 Determine how far the rafter travels HORIZONTALLY PLAN LENGTH For any Rafter (or Hip) you must first determine the Horizontal Travel For any Rafter (or Hip) you must first determine the Horizontal Travel i.e. PLAN LENGTH

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Principle Of Similar Triangles If all 3 angles of 2 triangles are equal There will be the same proportional difference between the corresponding sides of the triangle 25° The right hand triangle is 2x the size of the “1 meter triangle” 2x 65° 25°

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Understanding the Principle Of Similar Triangles 25° This is our “1 meter” triangle 65° 25°

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Understanding the Principle Of Similar Triangles 25° This is the TARGET triangle formed by the rafter 65° 25°

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Understanding the Principle Of Similar Triangles 25° The first step is to determine proportional ratio between the triangles 65° 25°

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Understanding the Principle Of Similar Triangles 25° The first step is to determine proportional ratio between the triangles To determine this we ALWAYS determine using the PLAN lengths 65° 25°

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Understanding the Principle Of Similar Triangles 25° The first step is to determine proportional ratio between the triangles To determine this we ALWAYS determine using the PLAN lengths Ratio = Plan length of “TARGET” triangle ÷ Plan length “1 metre” triangle 65° 25° 1 Metre Triangle Target Triangle

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Understanding the Principle Of Similar Triangles 25° The first step is to determine proportional ratio between the triangles To determine this we ALWAYS determine using the PLAN lengths Ratio = Plan length of TARGET triangle ÷ Plan length “1 meter” triangle Ratio = 2 ÷ 1 Ratio = 2 65° 25°

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Understanding the Principle Of Similar Triangles 25° The first step is to determine proportional ratio between the triangles To determine this we ALWAYS determine using the PLAN lengths Ratio = Plan length of TARGET triangle ÷ Plan length “1 meter” triangle Ratio = 2 ÷ 1 Ratio = 2 65° 25° We will call this the triangle multiplier

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Understanding the Principle Of Similar Triangles 25° The first step is to determine proportional ratio between the triangles To determine this we ALWAYS determine using the PLAN lengths Ratio = Plan length of TARGET triangle ÷ Plan length “1 meter” triangle Ratio = 2 ÷ 1 Ratio = 2 65° 25° For the Common Rafter as we use the “1 meter” triangle, the Triangle Multiplier will always = Plan length of the Target triangle

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Step 3 – Determine Rafter Length Centreline Length 25° 1 Rafter Length = Plan Length x Rafter Length per metre (RL/m) Rafter Length = 1350 x Rafter Length = ½ Span Plan Length 1489

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Step 4 – Determine Rise (If Required) Centreline Length 25° 1 Total Rise = Horizontal Travel x Rise per metre Total Rise = 1350 x Total Rise = (1/2 Span) Plan Length

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True Length Rafter 90 x 45 Ridge 125 x 19 What is the plan length we need to use to determine the True Length of the common rafter below ?

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True Length Rafter 90 x 45 Ridge 125 x 19 What is the plan length we need to use to determine the True Length of the common rafter below ?

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Determine Centreline Length Ridge 125 x19 True Length is to the Side of the Ridge ½ Span – ½ Ridge Thickness

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Step 2 – Determine Plan Length True Length 25° Plan Length “Plan Length” = ½ Span – ½ Ridge Thickness = 1350 – 9.5 = 1341 Determine how far the rafter travels HORIZONTALLY PLAN LENGTH Ridge 125 x 19

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Step 2 – Determine Plan Length Trur Length 25° (1/2 Span) Plan Length “Plan Length” = 1341 Determine how far the rafter travels HORIZONTALLY PLAN LENGTH For any Rafter (or Hip) you must first determine the Horizontal Travel For any Rafter (or Hip) you must first determine the Horizontal Travel i.e. PLAN LENGTH Ridge 125 x 19

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Principle Of Similar Triangles If all 3 angles of 2 triangles are equal There will be the same proportional difference between the corresponding sides of the triangle 25° The right hand triangle is 2x the size of the “1 meter triangle” 2x 65° 25°

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Understanding the Principle Of Similar Triangles 25° This is our “1 meter” triangle 65° 25°

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Understanding the Principle Of Similar Triangles 25° This is the TARGET triangle formed by the rafter 65° 25°

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Understanding the Principle Of Similar Triangles 25° The first step is to determine proportional ratio between the triangles 65° 25°

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Understanding the Principle Of Similar Triangles 25° The first step is to determine proportional ratio between the triangles To determine this we ALWAYS determine using the PLAN lengths 65° 25°

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Understanding the Principle Of Similar Triangles 25° The first step is to determine proportional ratio between the triangles To determine this we ALWAYS determine using the PLAN lengths Ratio = Plan length of “TARGET” triangle ÷ Plan length “1 metre” triangle 65° 25° 1 Metre Triangle Target Triangle

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Understanding the Principle Of Similar Triangles 25° The first step is to determine proportional ratio between the triangles To determine this we ALWAYS determine using the PLAN lengths Ratio = Plan length of TARGET triangle ÷ Plan length “1 meter” triangle Ratio = 2 ÷ 1 Ratio = 2 65° 25°

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Understanding the Principle Of Similar Triangles 25° The first step is to determine proportional ratio between the triangles To determine this we ALWAYS determine using the PLAN lengths Ratio = Plan length of TARGET triangle ÷ Plan length “1 meter” triangle Ratio = 2 ÷ 1 Ratio = 2 65° 25° We will call this the triangle multiplier

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Understanding the Principle Of Similar Triangles 25° The first step is to determine proportional ratio between the triangles To determine this we ALWAYS determine using the PLAN lengths Ratio = Plan length of TARGET triangle ÷ Plan length “1 meter” triangle Ratio = 2 ÷ 1 Ratio = 2 65° 25° For the Common Rafter as we use the “1 meter” triangle, the Triangle Multiplier will always = Plan length of the Target triangle

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Step 3 – Determine Rafter Length True Length 25° 1 Rafter Length = Plan Length x Rafter Length per metre (RL/m) Rafter Length = 1341 x Rafter Length = Plan Length 1479

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Step 4 – Determine Rise (If Required) Centreline Length 25° 1 Total Rise = Horizontal Travel x Rise per metre Total Rise = 1341 x Total Rise = Plan Length

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Overhang on a Plan is always measured from external wall

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Determine Rafter Length Mathematically (Version 1) Rafter 90 x 45 Ridge 125 x 19 Roofing calculations are always measured from Birdsmouth or pitching point In this case Timber Famed Wall Determine Rafter Length per m = 1 ÷ cos 25 = per m Rafter = Run x = x = 1.480

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Determine Rafter Length Mathematically Rafter 90 x 45 Ridge 125 x 19 Roofing calculations are always measured from Birdsmouth or pitching point In this case Timber Famed Wall Determine Total Rafter Length Rafter = Plan Length x = x = 1791 x = 1.975

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Rafter 90 x 45 Ridge 125 x 19 In this case Brick Veneer Wall O/H = = 600mm Determine Rafter Length Mathematically Total Rafter Length = x = 1961 x = 2.163

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Rafter 90 x 45 Ridge 125 x 19 Determine Rafter Length Graphically 1.Draw Roof Full-size 2.Measure members directly 3.Avoid using scaled drawing 4.Scale use only for angles

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Determine Rafter Length Mathematically Rafter 90 x 45 Ridge 125 x 19 Roofing calculations are always measured from Birdsmouth or pitching point In this case Timber Famed Wall O/H = 450 / cos 25 = 497mm

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Rafter 90 x 45 Ridge 125 x 19 In this case Brick Veneer Wall O/H = cos 25 = 662mm Determine Rafter Length Mathematically Total Rafter Length Timber Frame = = 1977mm Brick Veneer = = 2142mm

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Rafter 90 x 45 Ridge 125 x 19 Determine Rafter Length Graphically 1.Draw Roof Full-size 2.Measure members directly 3.Avoid using scaled drawing 4.Scale use only for angles

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Determine Rafter Length Using Roofing Square Use Calculator 1.Press Tan 25 – what does this give you 2.Therefore for every 1 metre run there is 0.466m rise 3.Using the principle of similar triangles we half the size of the triangle

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Use Calculator 1.Press Tan 25 – what does this give you 2.Therefore for every 1 metre run there is 0.466m rise 3.Using the principle of similar triangles we half the size of the triangle

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Use Calculator 1.Press Tan 25 – what does this give you 2.Therefore for every 1 metre run there is 0.466m rise 3.Using the principle of similar triangles we half the size of the triangle

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Using Similar Triangles 1341/500 = or = 2 r 341

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Using Similar Triangles 1341/500 = or = 2 r 341 Select Start Point Allowing for O/H Step out 2 full triangles

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Intersection of Top of Rafter & Edge of Square

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Using Similar Triangles 1341/500 = or = 2 r 341 Select Start Point Allowing for O/H Step out 2 full triangles Step out 341 & use square to extend

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Determine Roofing Angles used in Gable Roofs Plumb Cut Foot Cut

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Determining Angles with Roofing Square When we set out rafter previously we determined plumb cut

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Determining Angles with Roofing Square Plumb Cut Foot Cut

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Determining Angles Mathematically 1.Extend Line 90⁰ From Rafter

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Determining Angles Mathematically 1.Extend Line 90⁰ From Rafter 2.Extend Plumb Line

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Determining Angles Mathematically 1.Extend Line 90⁰ From Rafter 2.Extend Plumb Line 3.Angle Formed is same as roof pitch

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Determining Angles Mathematically Roof Pitch Right Angled Triangle This angle must be 65 ⁰ 90 – 25 = 65 This angle must be 25 ⁰ 90 – 65 = 25

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Determining Angles Mathematically 1.Extend Line 90⁰ From Rafter

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Determining Angles Mathematically 1.Extend Line 90⁰ From Rafter 2.Extend Plumb Line from same origin at top of Rafter

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Determining Angles Mathematically 1.Extend Line 90⁰ From Rafter 2.Extend Plumb Line from same origin at top of Rafter 3.Angle Formed is same as roof pitch

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Determining Angles Mathematically 1.Extend Line 90⁰ From Rafter 2.Extend Plumb Line 3.Angle Formed is same as roof pitch 4.Offset = Tan (pitch) x width

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Determining Angles Mathematically 1.Extend Line 90⁰ From Rafter 2.Extend Plumb Line 3.Angle Formed is same as roof pitch 4.Offset = Tan (25⁰) x 90 = 42

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Determining Angles Mathematically Next we can Determine our Birdsmouth 1.Width across plumb cut = 90/ cos = 99 3.Therefore max Birdsmouth = 33 4.Distance from top plate to top of Rafter = 66

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Complete Q5 in Workbook

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Determine Roof Angles Graphically Plan – View We can only see rafter run

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Determine Roof Angles Graphically Extend Top Plate & Ridge

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Determine Roof Angles Graphically Extend Top Plate & Ridge Mark Rise

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Determine Roof Angles Graphically Extend Top Plate & Ridge Mark Rise Draw Hypotenuse Plumb Cut Foot Cut

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Steps In Construction Gable Roof 1.Physically Confirm Span & Plates are Parallel 2.Calculate True Rafter, Rise & Plumb cuts 3.Mark out ceiling joists, rafters & ridge 4.Install Ceiling Joists 5.Cut Pattern Rafter & test to confirm 6.Cut required rafters & install

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Estimating Gable Roof - Rafter From Previous Ceiling Estimate Determine No of Ceiling Joists12 250/ 600 = = = Pitch = 25⁰ Therefore 22 set of Rafters = Verge = 48

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Determine Rafter Length Span = 6900 Pitch 24°

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Determine Rafter Length Span = 6900 Pitch 24° 1

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Determine Rafter Length Span = 6900 Pitch 24°

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Determine Rafter Length Span = 6900 Pitch 24° Rafter =√ ( )

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Determine Rafter Length Span = 6900 Pitch 24° Rafter =√ ( ) =

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Determine Rafter Length Span = 6900 Pitch 24° 1 Rafter =

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Determine Rafter Length Span = 6900 Pitch 24° 1 Rafter =1 ÷ Cos 24° 1.095

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Determine Rafter Length Span = 6900 Pitch 24° 1 Rafter =1 ÷ Cos 24° =

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Determine Rafter Length Span = 6900 Half Span = 3450

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Determine Rafter Length Span = 6900 Half Span = 3450 Run = 3450 – 9.5 (Half Ridge) =

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Determine Rafter Length Span = 6900 Half Span = 3450 Run = 3450 – 9.5 = True Length = / cos 24 =3766

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Determine Rafter Length Span = 6900 Half Span = 3450 Run = 3450 – 9.5 = True Length = / cos 24 =3766 Overhang = 450/cos 24 = 493

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Determine Rafter Length Span = 6900 Half Span = 3450 Run = 3450 – 9.5 = True Length = / cos 24 =3766 Overhang = 450/cos 24 = 493 Total Rafter = 4259

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Determine Rafter Length Span = 6900 Half Span = 3450 Run = 3450 – 9.5 = True Length = / cos 24 =3766 Overhang = 450/cos 24 = 493 Total Rafter = 4259 Allow for plumb cut = 41 Minimum Rafter Length = 4300 Order = 4500 Allow for Plumb cut Tan (Pitch) x Width = Tan 24° x 90 = 41

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Estimating Sheet

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Estimating Gable Roof - Purlin Pitch = 24⁰ Overhang 450 Rafter 90 x 45 F7 600 c to c Tiled Roof Ridge 140 x 19 Purlin 90 x 70 F7 Purlin Run full length of Roof Do we need purlins

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In First Instance we check single span Max Span = 1900 Span Required = 3766 Max Span /2600 = 1.4 Therefore 1 row required each side

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Estimating Gable Roof -Purlin Pitch = 24⁰ Overhang 450 Rafter 90 x 45 F7 600 c to c Tiled Roof with Flush Gable & Raking Eaves Ridge 140 x 19 Purlin 90 x 70 F7 Purlin Run full length of Roof Do we need purlins Purlins Run Full Length x 150 (Joins) =

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Estimating Sheet

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Estimating Gable Roof - Ridge Pitch = 24⁰ Overhang 450 Rafter 90 x 45 F7 600 c to c Tiled Roof with Flush Gable & Raking Eaves Ridge 140 x 19 Purlin 90 x 70 F7 Ridge Runs Full Length x 450 (O/H) x 300 (allow for joins) =14000mm Note – For Flush eaves there is no O/H ridge = Boxed eaves will require O/H ridge = 13400mm

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Estimating Sheet

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Estimating Gable Roof - Struts Pitch = 24⁰ Overhang 450 Rafter 90 x 45 F7 600 c to c Tiled Roof with Flush Gable & Raking Eaves Ridge 140 x 19 Purlin 90 x 70 F7 Span 2700 Struts are Difficult to Estimate Develop a Best Guest Method Determine No Required 12500/2700 = 4.6 = 5 = 6 Each Side

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Estimating Gable Roof - Struts Pitch = 24⁰ Overhang 450 Rafter 90 x 45 F7 600 c to c Tiled Roof with Flush Gable & Raking Eaves Ridge 140 x 19 Purlin 90 x 70 F7 Span 2700 Struts are Difficult to Estimate Develop a Best Guest Method Half Rise x √2 x √2 Tan 24⁰ x 3441 x 2 = 3064 Determine No Required 12500/2700 = 4.6 = 5 = 6 Each Side

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Estimating Sheet

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Estimating Gable Roof – Collar Ties Pitch = 24⁰ Overhang 450 Rafter 90 x 45 F7 600 c to c Tiled Roof with Flush Gable & Raking Eaves Ridge 140 x 19 Purlin 90 x 70 F7 Span 2700 Collar Ties 90 x 35 Collar Ties on Every 2 nd Rafter On top of Purlins 22/2 = HALF SPAN 3450

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Estimating Sheet

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Estimating Gable Roof – Verge Trims Pitch = 24⁰ Overhang 450 Rafter 90 x 45 F7 600 c to c Tiled Roof with Flush Gable & Raking Eaves Ridge 140 x 19 Purlin 90 x 70 F7 Span 2700 Collar Ties 90 x 35 True Length of Rafter

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Rafter True length / 600 = 6.28 = 7 (Ridge Closes) 1200 = 33.6 Say 33.9

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Estimating Sheet

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One Row of Purlin Each Side

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Gable Roof Common Rafter

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Top Plate Part of the Wall Frame Takes structural load from Roof Size must be determined from span tables

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Top Plate

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Exercise 1 Determine Required Top Plate Size

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Common Rafter Principles Birdsmouth Max 1/3 Depth of Rafter

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