Johnson-level-tool-mfg RAS-1 Bedienungsanleitung PDF herunterladen (Seite 11)

TABLE A

Change Inches to Feet

1" = .08' 7" = .58'

2" = .16' 8" = .67'

3" = .25' 9" = .75'

4" = .33' 10" = .83'

5" = .42' 11" = .92'

6" = .50'

STEP 3. CALCULATE INCH RISE:Forexample,withthe

Run=13'0"andRise=8'9".Firstconverttherisetofeet

indecimalform,usingTABLEA.Therefore,theRise=

8.75'.Now,usingtheformulaforthe“InchRise”:

8.75' x 12

Inch Rise = = 8.08 in/ft. Run

13'

Round o the Inch Rise to the nearest inch. Since rounding

o won’t make much dierence in most cases. It will make the

actualroofriseslightlyhigherorlower.Inthisexample,round-

ingto8willmaketheheight8'8"insteadof8'9".Roundingo

this ﬁgure has more of an eect on buildings with longer rafter

runs or higher roof rises. If the Inch Rise is given on a blueprint,

this calculation is not needed, just use the one given. Now, let

usdoanexampleofeachtypeofrafter.

COMMON RAFTERS

COMMON RAFTER LENGTH:

After the Inch Rise and Run are

found, use the tables in the back of this book to ﬁnd the com-

monrafterlength.Inourexamplean8InchRiseisused,there-

forendthe8InchRisetable(onpage47)andgodowntheleft

handcolumnheaded“RunFt.”andlocate13'.Totheright,read

thecolumnheaded“CommonRafterLength”fortherafter

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Johnson-level-tool-mfg RAS-1 Bedienungsanleitung Seite 11