Johnson-level-tool-mfg RAS-1 Manual de usuario descargar pdf (Pagina 8)

RAFTER MEASUREMENTS

The use of our square for rafter layout is based on two simple and

commonbuildingmeasurements:(1)therafterrun,and(2)the

rafter rise. These are available from either the building blueprints,

drawings, or actual measurements. The tables included in the back

of this book are also based on these two simple measurements

(seeFigures2and3,andalsothetablesstartingonpage40).

RAFTER RUN: Run is the horizontal or level distance the rafter

will span. It is measured in feet.

RAFTER RISE: Rise is the vertical distance of a rafter between

its highest and lowest points. It is measured in feet.

INCH RISE: The rise measured in inches per foot run. It is also

called“InchRisePerFootRun.”Itcanbecalculatedwiththe

following formula:

INCH RISE RAFTER RISE (ft) x 12

OR =

(SCALE NUMBER) RAFTER RUN (ft)

The Inch Rise gives you the corresponding scale number to use

onthesquare(forthecommon&hip-valscales).Itisalsothe“one

numberbywhichyoucanframetheroof.”

The inch rise, the rafter run and the tables in the back of the book

are all that are needed to lay out rafter lengths and the cuts for

common, hip, valley and jack rafters. The instructions outlined

below

show the step-by-step procedure to follow for basic roof

construction.

STEP 1. OBTAIN RAFTER RUN:

Measure or calculate the

horizontal distance the rafter will span, starting at the outside of

the wall on which it will rest. Include any boarding on the wall if it

extendstothewalltopplate(seeFigure3).

When measuring building width to obtain rafter run, use a steel tape

if possible so that you can measure the full width of the building.

Measure from outside to outside of the wall or the top plate on

whichtherafterwillrest.Ifboardingextendsuptothetopplate,

measurement is to be taken from outside of the boarding.

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Johnson-level-tool-mfg RAS-1 Manual de usuario Pagina 8