5. THE RAFTERS ARE THE MAIN STRUCTURE OF THE ROOF FRAME . THE RAFTERS SPAN ACROSS THE COMPLETE DISTANCE OF THE EXTERNAL WALL FRAMES. THE MAIN RAFTERS ARE CALLED COMMON RAFTERS .
7. THE HIPS ARE VERY SIMILAR AS RAFTERS EXCEPT THEY COME FROM THE CORNERS OF THE HOUSE EG: 45o THE HIPS ARE CUT AT THE SAME PITCH AS THE RAFTERS BUT HAVE A DIFFERENT PLUMB CUT. HIP RAFTERS-
12. CREEPERS ARE ALSO KNOWN AS CREEPER RAFTERS . THEY ARE THE RAFTERS THAT COME OFF THE HIP AT RIGHT ANGLES. EACH CREEPER HAS A SHORTENING AT THE SAME DISTANCE. CREEPERS
14. THE UNDER PURLIN IS FIXED UNDER THE RAFTERS AND 2/3rds UP THE ROOF SLOPE FROM THE TOP PLATES . TO ASSIST IN THE CORRECT POSITIONING OF THE UNDER PURLIN LOCATION LINES SHOULD BE SET OUT ON THE PATTERN RAFTER. UNDER PURLIN
16. PURLIN PROPS ARE THE UP RIGHT MEMBERS THAT SUPPORT THE ROOF LOAD. THEY SIT ON TOP OF A WALL PLATE AND CONNECT TO THE UNDER PURLIN THIS IS CALLED A POINT LOAD AND SHOULD BE SUPPORTED TO THE GROUND. PURLIN PROPS
18. CRIPPLE CEEPERS ARE SIMILAR TO CREEPERS ALTHOUGH THEY START FROM THE RIDGE OR FLYING HIP AND FINISH AT THE VALLEY. THE DIFFERENCE BETWEEN THE CREEPER AND THE CRIPPLE CREEPER IS THAT THERE IS NO BIRDSMOUTH CUT . IT IS A STRAIGHT PLUMB CUT AT ONE END AND A REVERSED CREEPER CUT AT THE OTHER. CRIPPLE CREEPERS
20. COLLAR TIES ARE USED TO TIE THE OPPOSING RAFTERS TOGETHER. TO STOP THEM FROM DROPPING AND FALLING APART. COLLAR TIES ARE SET INTO POSITION 2/3rds UP THE ROOF SLOPE AND SIT ON TOP OF THE UNDER PURLIN, THEN NAILED. COLLAR TIES
21. RAFTER LENGTH CALCULATION EXAMPLE. FIND THE SPAN EXAMPLE 6000 mm FIND THE 1/2 SPAN EXAMPLE 3000 mm FIND THE 1/2 SPAN MINUS 1/2 RIDGE THICKNESS EXAMPLE 3000mm MINUS 19mm = 2981 mm
22. RIDGE SIZE = 175 X 38 ROOF PITCH = 40 deg 2’ BUILDING SPAN = 6000 mm BUILDING HALF SPAN = 3000 mm = 2981 mm = 3892 mm ROOF FRAMING
23. 1/2 SPAN MINUS 1/2 RIDGE THICKNESS = 2981mm 2000 mm = 2612 mm 900 mm = 1175 mm 80 mm = 104mm 1 mm = 1 mm TOTAL RAFTER LENGTH = 3892 mm ROOF FRAMING
