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Types of Roofs and Cutting Common Rafters

Types of Roofs and Cutting Common Rafters. Dr. David Agnew Arkansas State University. Types of Roofs: In Agricultural Applications. Hip Gothic Combination Uneven span. Types of roofs. Types of Rafters. Parts of A Roof….. . Definition of a Rafter.

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Types of Roofs and Cutting Common Rafters

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  1. Types of Roofs and Cutting Common Rafters Dr. David Agnew Arkansas State University

  2. Types of Roofs:In Agricultural Applications Hip Gothic Combination Uneven span Types of roofs

  3. Types of Rafters

  4. Parts of A Roof…..

  5. Definition of a Rafter • Single timber supporting a roof section.

  6. Kinds of Rafters

  7. Parts of a Rafter

  8. Rafter Slope • Roofs are not flat • Pros and cons of low or steep roofs • Cost of steep is higher for materials • Harder and more dangerous to work on if steep • Steep roofs have greater ability to withstand load • Pitch • Expressed as a Fraction ¼, 1/6, 1/8, etc. • Rise/foot of run • Example: 2 in./ ft. • Used in more plans today than pitch

  9. Calculating Pitch

  10. Procedures for Rafter Layout • Three Techniques • Stepping method • Figuring length using A2 + B2 = C2 • Rafter Table

  11. Procedures for Rafter Layout • Three Techniques • Stepping method # steps= feet of run Ex 10 12 etc. Step 1 2 3

  12. Procedures for Rafter Layout • Three Techniques • A2 + B2 = C2 2 C 2 B A 2 A= Run of Roof Example: If A=4 , B=3 then what would c=? 16 + 9 = 25 then C= sq root of 25 which is 5

  13. Resources Needed to Layout and Cut a Rafter • Timber/Lumber (2x4, 2x6, 2x8, etc) • Measuring Device-- Tape Measure • Marking Pencil • Rafter/Carpenter’s Square • Saw • Sawhorses • Note: The class project rafter layout will need some different supplies.

  14. Steps to layout of Rafter Using the Rafter Table. • Determine Rise or Pitch • Determine the Span and/or Run • Using the table for common rafters on the Rafter Square Identify the length of rafter per ft of run.

  15. Rafter Layout Continued • Multiply the run times the number from the table. That number is the length of the rafter… But you are not done yet… • Identify the end of the board that you want to make the ridge cut. • The square has a tongue and a body • Tongue is the smaller of the two 18 inches long and 1 ½ inches wide. • Body is larger 24 inches long and 2 inches wide.

  16. Parts of a Framing or Rafter Square 1.5 inches thick Tounge • inches thick 18 " Body 24 "

  17. Proper Use of the Square • Always work from one side of the square (never flip it over). • Remember to either use the numbers from the outer edge or inner edge, but do not use both at one time.

  18. Ridge Cut • Using the appropriate numbers on the square (ex. 4 and 12) place the square near the end of the board where the cut is to be made. See picture below.

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