IRWINÂ® Rafter Square Reference Guide Complete Instruction Book ...

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The procedure for basic roof construction is as follows (See figure 4.):1. Obtain Rafter Run: Measure or calculate the horizontal distance the rafterwill span, starting at the outside of the wall on which it rests and including anyboarding on the wall if it extends to the wall top plate.2. Obtain Roof Rise: Measure, calculate, or obtain from the blueprints thedistance in feet the ridge will be from the top of the wall.Use the following table to convert inches to feet:Convert Inches to FeetINCH RISE(SCALE NUMBER)1" = .08' 4" = .33' 7" = .58' 10" = .83'2" = .16' 5" = .42' 8" = .67' 11" = .92'3" = .25' 6" = .50' 9" = .75'3. Calculate Inch Rise: Using the table above, convert rise to feet in decimalform and calculate using the Inch Rise Formula.EXAMPLE: Run = 15'; Rise = 8'8" or 8.67'8.67 (ft) x 1215 (ft)==RAFTER RISE (ft) x 12RAFTER RUN (ft)6.94 in/ft. RunYou may round off Inch Rise to the nearest inch, which can make the actual roofrise slightly higher or lower but will not matter in most cases. If the Inch Rise isprovided on a blueprint, the previous calculation is not needed.With the Inch Rise calculated, we are now ready to layout each type of rafter.7
[Fig. 4 – The Common Rafters]PLUMB CUTAWITHOUT RIDGERAFTER LENGTHRISETAILOREAVERUNSEAT NOTCHSET ON TOPPLATETAIL RUNPLUMB CUTBWITH RIDGERAFTER LENGTHTAILOREAVE90°RUNRISEINCH RISE PERFOOT RUN=RISE x 12RUNTAIL RUNRAFTER LENGTH = RUN 2 + RISE 2(FIND IN TABLES)FIGURE 4: Common Rafter8
Page 1 and 2: IRWIN ® Rafter Square Reference Gu
Page 3 and 4: DIAGRAM OF RAFTER SQUAREMARK ALONGT
Page 5 and 6: [Fig. 1 - Types of Rafters - 3D]DOR
Page 7: USING THE RAFTER SQUAREThe use of t
Page 11 and 12: Common Rafter Layout1. Top Plumb Cu
Page 13 and 14: HORIZONTAL ORBOTTOM CUT[Fig. 8a - S
Page 15 and 16: BEVEL CUT[Fig. 10 - Hip Rafter Layo
Page 17 and 18: 3. Tail or Bottom Plumb Cut: Measur
Page 19 and 20: RIDGE[Fig. 12 - Top View ofValley R
Page 21 and 22: [Fig. 14 - Top Viewof Hip Jack Raft
Page 23 and 24: DORMER RAFTERSWhen remodeling or ad
Page 25 and 26: 1 INCH RISE 1-12 PITCH 4 3 ⁄4 DEG
Page 27 and 28: 3 INCH RISE 3-12 Pitch 14 DegreesCo
Page 29 and 30: 5 INCH RISE 5-12 PITCH 22 1 ⁄2 DE
Page 31 and 32: 7 INCH RISE 7-12 PITCH 30 1 ⁄4 DE
Page 34 and 35: 10 INCH RISE 10-12 PITCH 40 DEGREES
Page 38 and 39: 14 INCH RISE 14-12 PITCH 49 1 ⁄2
Page 48: 24 INCH RISE 24-12 PITCH 63 1 ⁄2

IRWINÂ® Rafter Square Reference Guide Complete Instruction Book ...

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