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Questions &Answers
Use 7-lO Rule to Lay Out Stainvay Stringers
Is there an edsy way to calculate
how to cut stair stringers to
_fitfrom ground leuel to a plat-
.form 9-ft. aboue the ground?
Mario Arena
Scipio Center, NY
Many books have been
written on the subject of
building stairs - such as
Basic Stairbuilding by Scott Schuttner
(1990,tunton Press) - but here's
a very briefoverview. You need to
use something called the 7-10 rule.
It says that, in general, individual
steps should be 7" high (unit rise)
and 10" wide (unit run). However,
you'll have to adjust things to fit.
To do this, you divide the total
rise (the vertical distance between
levels, including finished flooring)
by 7". In your case, the total rise is
108" (9 ft. x 72" per ft.), which
when divided by 7" gives you
15.429.In round numbers, that
makes 15 steps.To get the actual
rise for each step (unit rise), divide
the total rise by the number of
steps - 108 = l5 = 7.2. or just a
-1l r'
nalr OVer / -'l t6
'With
unit rise calculated, you can
figure the unit run.The rule of
Waste
Stdnger
thumb is that the sum of one riser
and one tread width should be 17"
to 1 8". In your case, the unit run
could be 913/rr," (77 -73/rc) to
7013/tr," (18 - 73/r,). For simpliciry
let's use 10".To find total run, nrulti-
ply the unit run by the number of
steps (15);your total run would be
150". Which finally brings us to the
Position dog at
unit rise distance
Posltlon do$ at
run distance
stringers that support the stairs.
Stringers are usually cutfrom2xT2
stock. The length is determined as
shown, with extra at each end for
waste. Layout each step using a
framing square.You'lI need to sub-
tract the thickness of one stair tread
fiom the bottom end so the first and
last steDs will have the correct rise.
SI|ARE YOUR OIJE$TIOII$!
IJ_GUSTHOME:fi ::L'f
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