Gable Roof

1. Gable Roof BCGCA3007B

2. Gable Roof • Flush with no eaves • Flush with raked eaves • Boxed

3. 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

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

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

6. VergesIs the Junction of the Roof and the Barge/Verge Board Verge Detail for Tiled Roof

7. Verge Detail for Tiled Roof

8. Principles of Roofing Ridges are Level Rafters run at 90 Hips & Valleys bisect all internal & external Corners Roof members are set out along centerlines

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

10. 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 2 x 75mm Skew & 2 x 75mm into Ceiling Joist (if joist is > 38, 90mm Nails)

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

12. 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

13. Joining Ridge Boards

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

15. 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

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

18. Struts • Transfer Loads to Load Bearing Walls

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

24. Collar Ties

25. Common Rafter Principles Birdsmouth Max 1/3 Depth of Rafter

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

27. Common Rafter Principles True Rise –From Horizontal line that passes thru the Intersection of Birdsmouth Plumb Line &Top of Rafter To : vertically plumb up to the Apex NOTE – True Rise is not measured from TOP PLATE

28. A Closer Look Top Of Rafter Birds Mouth Top Plate Ceiling Joist NOTE – True Rise is not measured from TOP PLATE

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

30. Common Rafter Principles Pitching Line x-y line

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

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

33. Determine Rafter LengthMathematically Determine Span = 2700mm Determine Half Span = 2700/2 = 1350mm Determine Rafter Run = 1350- Half Ridge Thickness = 19/2 = 9.5 Rafter Run = 1341.5 True Length Rafter = 1341.5 / Cos 25 = 1480 Rafter 90 x 45 Ridge 125 x 19

34. OverhangPlan always from external wall

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

36. Determine Rafter LengthMathematically In this case Brick Veneer Wall O/H = 450 + 40 + 110 cos 25 = 662mm Total Rafter Length Timber Frame = 1480 + 497 = 1977mm Brick Veneer = 1480 + 662 = 2142mm Rafter 90 x 45 Ridge 125 x 19

37. Determine Rafter LengthGraphically Draw Roof Full-size Measure members directly Avoid using scaled drawing Scale use only for angles Rafter 90 x 45 Ridge 125 x 19

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

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

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

41. Using Similar Triangles 1341/500 = 2.682 or = 2 r 341

42. Using Similar Triangles 1341/500 = 2.682 or = 2 r 341 Step out 2 full triangles Select Start Point Allowing for O/H

43. Intersection of Top of Rafter & Edge of Square

44. Using Similar Triangles 1341/500 = 2.682 or = 2 r 341 Step out 341 & use square to extend Step out 2 full triangles Select Start Point Allowing for O/H

45. Determine Roofing Anglesused in Gable Roofs Plumb Cut Foot Cut

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

47. Determining Angles with Roofing Square Plumb Cut Foot Cut

48. Determining Angles Mathematically Extend Line 90⁰ From Rafter

49. Determining Angles Mathematically Extend Line 90⁰ From Rafter Extend Plumb Line

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