AN
EASY METHOD FOR LAYING OUT RAFTERS - ULTRA SQUARE |
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There are typically three cuts for rafters - the seat,
heel, and full plumb cuts. Also, there are typically four types of rafters
- common, hip, valley, and jacks. When marking rafters it is required to
subtract half the ridge thickness (3/4” for a 2x ridge) to mark the plumb
cut. For a common rafter this distance is 3/4” measured along the run line
(horizontal distance). For hip, valley and jack rafters this distance is
3/4” measured along the run times 1.414 (the distance for a 2x board cut
at 45º).
To simplify these measurements and increase
accuracy these calculations are
designed into the Ultra Square and may
be accomplished in one setting!
DETERMINING RAFTER LENGTH USING UNIT RISE TO UNIT RUN
- (PITCH).
For this example the total building span is 23 feet and the total rise
is 5 ¾ feet (5'9 "). First we must determine the total run. This is
half the buildings span (measured from the outside of the top wall plates)
which is 11½ feet (11'6"). Therefore, pitch is (rise/run) 5 ¾ feet
divided by 11½ feet =0.5 feet of rise per foot of run which is 6” in 12”
for a 6-12 pitch. There are two ways to determine a rafter’s length once
you know the pitch. The first is to use tables to look up the length for
the proper pitch. Using a table we obtain our common rafter’s length of
12 feet 10 and 5/16 inches. Also our hip length is equal to 17 feet 3 inches.
Another method of determining rafter lengths is to calculate them using
a builders calculator or use mathematical formulas.
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This RAFTER SQUARE is for the Handyman, Homeowner, or Professional and once you get the Ultra Square you will wonder how you did without it! Professionals can save $1000 with extended use!
If you have comments or suggestions, Email me at Ultra Square
This page created By R.B.