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Created BY Michael Martin July 2004 / revised may 2007 / reviewed & updated March 2010.

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Presentation on theme: "Created BY Michael Martin July 2004 / revised may 2007 / reviewed & updated March 2010."— Presentation transcript:

1 Created BY Michael Martin July 2004 / revised may 2007 / reviewed & updated March 2010

2  “4 Basic Principles”  All ridges must be level & parallel to wall plates  All rafters must be placed at 90° to wall plates – regardless of the roof shape  All hip and valleys must bisect the angle of the corner  Roof members are set out on centre lines

3  Wall plate  Ridge  Centering rafter  Crown end  Hip  Common rafters  Creepers  Purlin  Etc. 1Ridge board (Major roof)9Crown-end rafter 2Collar tie10Creeper rafter 3Common rafter11Valley rafter 4Centring rafter12Ridge board (Minor roof) 5Top plate13Common rafter (Minor roof) 6Fascia14Valley creeper rafter 7Hip rafter15Valley cripple creeper 8Purlin16Trimmer for minor ridge fixing

4 Centring rafter Ridge Crown end rafter Hip

5 Centering rafter Ridge Centering rafter Crown end rafter

6  Hip – Inclined member from wall plate at external corner to end of ridge  Crown end rafter – special rafter running from wall plate (center span position) to end of ridge  Creeper rafter – rafter cut in length to join hip

7  Ceiling frame also depends on set out of rafters  Set out as opposite  Textbook reference – P. 52 Ceiling joists Set out of rafters Half span Set out of rafters

8  Length = length of the building – width of building + rafter width

9  Now include  Common / centering  Crown end rafter  Creeper rafters

10  Remember  Common / centering – reduce by ½ thickness of ridge  Crown End – reduce by ½ thickness of common rafter / centring rafter  Creepers – are calculated on pattern – by determining long point

11 Long point for 1st Creeper Half thickness of Common Rafter RIDGE Spacing CROWN END RAFTER Half mitre thickness of Hip CROWN END RAFTER RIDGE Half thickness Common rafter Half mitre thickness hip 1st Creeper Spacing Hip CENTRING RAFTER

12  1 st mark out spacing from centre line  2 nd take off half mitre thickness of hip  3 rd add on half thickness of common rafter  You now have long point  Continue to mark out other creepers  Look at next slide

13 Long point for 1st Creeper Half thickness of Common Rafter RIDGE Spacing CROWN END RAFTER Half mitre thickness of Hip CROWN END RAFTER RIDGE Half thickness Common rafter Half mitre thickness hip 1st Creeper Spacing Hip CENTRING RAFTER

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15 Rise ½ span Plumb bevel Level bevel

16  Create another triangle in the roof Rise Plan length hip Plumb bevel Level bevel

17  Relate to true length per metre again  As you do for common rafter

18  Rise per m run – tan 30° =.577  Use Pythagoras to create plan length of hip  √1.0² + 1.0² = (plan length of hip)  True length per run  √1.414² +.577² = 1.527

19  You have now created that new triangle  You can reduce this to fit steel square  Take bevels from this Rise.577 Plan length hip True length 1.527

20  You now have your first four bevels › Plumb bevel common rafter › Level bevel common rafter › Plumb bevel hip › Level bevel hip  In a hipped roof, there are eight (8) bevels all up – plumb bevel common rafter, level bevel common rafter, plumb bevel hip, level bevel hip, edge bevel hip, edge bevel creeper, face bevel purlin & edge bevel purlin

21  These 8 bevels can be developed in a number of ways  Eventually you’ll choose which one that suits you › Geometric (we will draw ourselves) › Steel square › Direct method › Or combined triangles (not in text)  We will cover each one separately, one by one later

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23  1 st lets concentrate on what we know › Common rafters › Centering rafters › Hips › Creepers › ridge

24  Common rafters – set out on pattern  Crown end rafters – set out on pattern  Creepers – set out on pattern  Hips – we need to look at further

25  Before you erect hip  You have to take into account  Reductions  Ref: P16

26  1 st at the ridge the hip must be reduced in length  You can calculate it or  Measure it in place  In principle it is reduced as shown opposite  Hand out – shortening at “x”

27  2 nd at the birdsmouth you must reduce as well  Calculations of length give you position at outside of plate  Typically you cut corner to give better seating  Therefore birdsmouth must be reduced to suit  Handout – shortening at “y”

28  Set-out of birdsmouth on hip  Top of rafters, including hips, must be on the one plane  Set out of hip birdsmouth as opposite  See handout

29  Now you can build the main structure of the roof  Edge bevels for creepers and hips we’ll show you in workshop  Purlins we’ll look at after we develop other bevels  Drawing boards next week


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