These stairs call for
2x10 treated material for the rot-resistant notched stair stringers (also known
as jacks or carriages,
Photo 1) that
won’t be seen. This design also uses 2x12 skirt boards that attach to the sides
of the outside stringers. The skirts serve several purposes:
-
Cosmetically, they hide the unsightly notched, treated
stringers to make your stairs look polished.
-
They make it easy to attach the
stringers.
-
Structurally, they make for rock-solid stairs by
reinforcing the stringers, which have been weakened by
notching.
-
And when it comes time to attach guardrails and handrails
to the stairs, you’ll have a solid board to fasten pickets or posts to for a
wobble-free rail. (If you’d rather not use the 2x12 skirt boards, be sure to
use 2x12s for the notched stringers for adequate
strength.)
Tip
Remember, you need one right and one left
skirt assembly, not two lefts or
rights.
For the parts that show—the skirts, treads and risers
(lead photo)
—choose material that matches the deck. In our case, that was
cedar.
A Carpenter’s Square and a Set of Stair Gauges Are
Crucial
You’ll need a 4-ft. level, tape measure, calculator,
circular saw and a handsaw. If you don’t already have a carpenter’s square,
now’s the time to buy one ($10;
Photo 2). To do
the job right, pick up a set of stair gauges ($5), too. Stair gauges are little
clamps that you tighten onto the square at the proper rise (vertical stair
height) and run (horizontal tread depth) for exactly duplicating each step as
you draw it onto the stringers (Photo 2). The
gauges save time and ensure that all the steps are
consistent.
Designing Safe, Comfortable Stairs
Building codes contain specific requirements for safe
stair design. If you follow the directions in this story, your stairs will be
legal and safe. In a nutshell, treads should be more than 9 in. deep and risers
6-1/2 to 8 in. high. Riser heights can vary no more than 3/8 in. from one step
to another to reduce trip hazards. However, even a 1/4-in. variation can
cause tripping.
Converting Decimals to Fractions
Not many calculators are set up to give you fractions,
and a readout like 7.65 isn’t much help for setting the carpenter’s square and
stair gauges. Use this chart to help you convert the readout to fractions or
for converting fractions to decimals for calculator
entries.
Choose whichever fraction is closest to the decimal
reading for setting your gauges when you lay out your
stringers.
.125 = 1/8 in.
.25 = 1/4
in.
.375 = 3/8 in.
.5 = 1/2
in.
.625 = 5/8
in.
.75 = 3/4
in.
.87 = 7/8
in.
Decide on the Width of the Stairs and How Many Stringers You’ll
Need
If you use 2x6s for tread material like we show, you can
build stairs up to 48 in. wide with only three stringers because 2x6s can span
up to 2 ft. But if you use the common and thinner 5/4-in. bull-nosed decking
for your treads, you’ll have to keep stringers no more than16 in. apart and
you’ll be limited to 32-in. wide stairs with three stringers. For wider stairs,
add one or more evenly spaced stringers depending on the width of your stairs
and the tread material you choose.
Buying the Materials
Measure from the deck rim to the landing spot and add 2
ft. Buy three treated 2x10s, two 2x12 skirts and two 2x4s sized to the next
larger length and you’ll have plenty of material to work with (the worst mistake
is buying material that’s too short!). Get a 6-ft. 2x6 for securing the stairs
to the deck (Photo
8). You’ll also need two 2x6s for each tread and a 1x8 for each
riser. Use 3-in. deck screws to fasten the skirts and treads to the stringers
and the skirts to the deck. Fasten the risers to the stringers with 8d
galvanized nails.
For extra-strong stairs, reinforce the middle 2x10
stringer with 2x4s nailed to both sides (Photo 7).
There are a million ways to fasten the stringers solidly
to the deck.
Photo 8 shows a
simple, foolproof, extra-strong method that works especially well even for
open-sided stairs built without skirts.
There you go—a pretty, rock- solid set of stairs ready
for balusters and railings.
