I've been building stairs inside homes and on decks for almost 30
years. There are lots of viable methods that avoid the pitfalls
that lead to uneven risers, tilted staircases, and downright
collapses; in this article, I describe my practices for building a
set of stairs with cut stringers (stringers notched out for treads
and risers), probably the most common type of stringers used on
decks. I reference the 2009 International Residential Code (IRC);
your local code may differ.
Establish the Landing First
Where I work, the grade at the end of a deck staircase often
slopes, which means I have to establish where the bottom step will
land before I can determine the overall rise of the stair. So
rather than calculate a set of stairs and try to sort out the
landing afterward, I lay out the landing first and cut the stairs
I start by taking a rough measurement from the elevation of the
deck's surface plumb down to where I judge the landing should go. I
divide that number by 7 3/4 inches (the maximum permitted riser
height) and round the answer to the next highest integer to
determine the number of risers I'll need. For example, a total
estimated rise of 52 1/2 inches divided by 7 3/4 inches equals
6.77, which rounds up to seven risers. I subtract one to get the
number of treads (unless the top tread is an extension of the deck
surface, there is always one less tread than there are risers).
Then I multiply the number of treads by my selected tread depth
(usually 10 inches, the minimum per the code) to determine
precisely how far away from the edge of the deck the last riser
It's not difficult to locate the landing when the grade is level or
slightly sloping, but on steep grades, I sometimes have to
recalculate because my first guess for the landing area or height
doesn't work out.
Once you know the position of the bottom riser, you can determine
the landing's finish grade level based on the surrounding earth.
Keep in mind these often-overlooked code provisions: A solid,
stable landing surface is required to extend at least 36 inches
beyond the bottom step, and the landing should slope for drainage
but no more than 1/4 inch per foot. Depending on how the work
progresses, I may form and pour the landing before laying out and
cutting the stringers (Figure 1). Other times, I make a mark on a
grade stake indicating the top of the landing, measure to the mark,
and cut the stairs.
Figure 1. After making preliminary
calculations to find the location of the base of the stairs, the
author pours concrete for the landing.
When I form and pour a landing, I use enough concrete to make it at
least 4 inches thick, and I broom-finish the top for traction. In
some locales, inspectors require the landing to be on frost
footings, but this isn't an issue my local building departments
have raised. If you don't regularly pour concrete or set hardscape
materials for a landing, consider these benefits - a level surface
for a precise total rise measurement and a stable footing to rest
the staircase on. And the last thing you want is for the staircase
to end on bare earth or lawn, because it will only be a matter of
time before the landing looks like the area under a children's
Stair stringers are laid out from finish level to finish level.
With the landing elevation pinpointed, I measure the total stair
rise from the landing finish level to the top of the decking. I
always lay a piece of finish decking on top of the joists to
measure from; otherwise - if I measure off the deck frame - I might
forget to add in the width of the decking. For decks close to the
ground, I place a level across the finish decking and just measure
down from it to the landing. On tall decks, since my level doesn't
reach out far enough, I set a laser atop the finish decking and
measure up from the landing to the light beam; then from that
measurement I subtract the distance between the base of the laser
and its beam (Figure 2).
Figure 2. Use a laser level and a tape to
accurately measure the total rise between the landing and the top
of the finish decking.
Like floor joists or rafters, stringers of a certain size and
spacing can span only so far, depending on the type of stringers
(cut or solid) and the species of wood. Also, because deck stairs
may be exposed to water, the maximum allowable span has to be
reduced because of the "wet-service" factor. Unlike joists or
rafters, however, stringers don't have an IRC table for determining
Rather than consult an engineer, I rely on the Prescriptive
Residential Wood Deck Construction Guide (DCA 6) from the
American Forest & Paper Association's American Wood Council
(free at awc.org/publications/DCA/DCA6/DCA6-09.pdf).
Since the AWC develops the standards for wood frame construction
that the IRC is based on, most building officials will accept the
DCA 6 criteria as an alternative to the IRC.
According to DCA 6, 2x12 southern-pine cut stringers are allowed a
7-foot span measured horizontally from the face of the bottom riser
to the back cut at the stringer head. Other woods are limited to
6-foot spans for cut stringers. As a practical matter, that means
the total rise of a cut set of southern-pine stringers is limited
to about 5 feet 10 inches. Western treated wood species are limited
to a total rise of about 4 feet 6 inches. That does not mean your
decks can't be higher than that, only that you may need to add
intermediate supports and footings for longer stringers.
Choosing and Laying Out Stringers
I'm choosey about stringer stock. The southern pine stocked at East
Coast lumberyards tends to be knotty and may be warped, cupped, and
twisted. I order #1 grade or hand-select 2x12 stringer stock,
avoiding lumber with large knots that can crack and drop out on a
cut stringer. Stock with crisp corners and no wane is hard to come
by but necessary if you want to use stair nuts on a framing square
to do the layout - stair nuts ride down into any wane void, and
they fail to register the top edge of the board on heavily eased
edges (Figure 3).
Figure 3. Stair nuts used on a framing square can
be handy for marking out risers and treads, but stringer wane and
eased edges make them difficult to use accurately.
Rather than struggle eyeballing the alignment, though, I gave up
stair nuts years ago in favor of a straight 1x2 fastened to a
square at the pitch of the stair. The 1x2 rides along the stock,
bridging heavy wane and any surface defects. I attach the 1x2 with
3/4-inch pan-head screws to a framing square in which I've drilled
a series of holes (Figure 4). Alternatively, a pair of small spring
or bar clamps work. Either way, align one end of the 1x2 with the
rise dimension and one end with the run dimension on the outside of
Figure 4. Rather than use stair nuts for
marking out stringers, the author prefers to screw a straight 1x2
to a framing square. The 1x2 bridges any wane or other edge defects
and provides a straight line that makes it easy to pinpoint riser
and tread points when stepping off the stairs.
One nice thing about using a 1x2 straightedge is that you can
easily register the square to the previous tread or riser line on
the stringer stock, because the 1x2 gives you a precise cross point
with the square that stair nuts don't. I generally start laying out
the stringer near the top with a tread cut mark. The point where
this mark trails off the edge of the stringer blank is where I
start the stepping-off process with the framing square: riser,
tread, riser, tread.
Even though the 1x2 works better than stair nuts, the eased edge of
the framing lumber and the presence of edge wane still make it hard
to align the points by looking straight down at the square. Often
you have to eyeball the tread mark on the stringer from the side to
align it with the riser dimension on the square, or else run a
separate straightedge (such as the blade of another square) along
the tread mark to bridge the air space over the edge ease or
I know the code allows us to be off a whopping 3/8 inch from the
shortest riser to the tallest one along a stringer, but I don't see
any benefit to being sloppy; it takes only a few extra seconds to
do a perfect layout job. Along those lines, I keep the pencil lead
sharp during the mark-out process, touching it up after every
half-dozen strikes. I also avoid running the pencil lines long at
the inside corner where tread meets riser to ward off the tendency
to follow the line to the bitter end when making saw cuts.
Since the deck's rim joist serves as the top riser on most of my
stairs, the stringer has no top riser cut. I count the tread marks
(as opposed to the riser marks) on the stringer to keep track of
how far to mark out. I've confused myself more than once when
laying out stairs, by accidentally marking a top riser, only to end
up cutting a stringer that's one step too tall (that is better than
too short, but I hate to toss a piece of wood, especially if I've
figured my stringer stock close).
The bottom riser cut on a stringer must be shorter than the rest by
the thickness of the tread stock, which "drops" the entire stringer
vertically by that much; once the treads are applied, the riser
heights will be equal, from the bottom step to the deck (Figure 5).
Housed stringers are laid out slightly differently (see
"Housed-Stringer Exterior Stairs," January/February 2007; deckmagazine.com.)
Figure 5. Mark the bottom cut on the stringer
so the bottom riser is shorter than the other risers by the
thickness of the tread stock. Here, the dotted line indicates the
full riser height as the author marks the cut line 1 1/2 inches
shorter to account for the 2x12 tread stock.
Some carpenters like to nail a 2x12 to the very bottom of the
stringer. If you do this, the stringers need to be trimmed off to
account for the thickness of the board. The same is true for any
mounting bracket you install. If the bracket elevates the stringer
off the landing then you'll need to trim the stringer bottom - even
if it's just 1/4 inch.
When you plan the stringer head cut, think about how you'll attach
the stringer to the deck. Many common stringer attachment practices
wouldn't pass an engineer's sniff test, nor would they strictly
adhere to the building code. I use a couple of attachment
configurations that rely on metal connectors specifically designed
and tested for mounting stringers to the deck frame (more on that
later). Both of my methods mount the stringers directly to the deck
rim board or to a header set just beneath the rim board. In either
case, I cut the stringer head square down from the back of the
tread cut (Figure 6).
Figure 6. Mark the head cut plumb down from
the back of the top tread cut.
I like to make one final check before notching out the riser and
tread cuts. I cut just the head and foot of the stringer and
position it against the deck frame to make sure my calculations and
layout are on track (Figure 7). While this step won't save the
stringer stock if you've cut it too short, at least it saves the
time of notching a majority of the cuts. And you may be able to
salvage at least some of a mis-cut stringer and repurpose it for
Figure 7. The author makes the plumb head cut
and level foot cut first, then positions the stringer between the
deck and the landing to double-check the fit before notching for
treads and risers.
Cutting stringers is pretty straightforward. Still, I've refined
the process to what works best for me and gives me the most
accurate results. First, the saw and blade have to be up to the
task. Because saw blades are sometimes out of square with the base
plate by a degree or two, I double-check that angle with a framing
square and, if necessary, adjust the base. A sharp saw blade is
essential; the saw enters the cuts and tracks truer when the teeth
are sharp. I often swap out a regular framing blade for a 24-tooth
thin-kerf crosscut blade before I cut stringers.
The closer the saw blade lines up with the angles of the treads and
risers when starting the cuts, the straighter the cuts will be. I
find that a consistent body angle aids in this, so I make all the
tread cuts first and make the riser cuts on a second pass along the
stringer (Figure 8). The rhythm of making the same entry angle each
time, rather than reorienting the saw 90 degrees, helps me keep the
cuts clean. The accuracy is well worth the extra minute it takes
for the second pass.
Figure 8. Making all tread cuts in succession,
then cutting the risers on a second pass along the stringer, helps
the author repeat a consistent entry angle for the meticulous
It is very important not to overcut the inside corners where tread
and stringer cuts come together. Overcuts reduce the cross-section
strength of the stringer and can lead to cracking. I often bore
holes with a 3/4-inch bit where the riser and tread cuts meet so
that each hole just touches the edges of both lines. This leaves a
radius at the inside corner and an obvious visual cue to stop the
cut. When I don't bore holes first, I stop the saw kerf 1/8 inch to
1/4 inch short of the intersecting lines (Figure 9) and finish the
cut with a pull saw, being careful not to overcut the corner
Figure 9. Stop saw cuts 1/8 inch to 1/4 inch
short of the opposite lines to avoid overcutting the
Figure 10. Finish the inside corner cuts with
a handsaw, taking care not to overcut the corner.
Since I use the first stringer as the pattern for marking the
others, I cut it as precisely as possible. When I align the pattern
stringer with the stock for the duplicates, I make sure the cut
sides are flush even if the stock depth isn't equal; misaligned
bottom edges won't affect the stringer match. Then I clamp or screw
the pattern stringer to the duplicate stock to reduce the chance of
them going out of alignment while I'm drawing the cut lines,
especially on longer sets of stringers. I use a sharp pencil, and
as the pencil marks are on the "waste" side of the notches, I take
the line with the saw blade when cutting.
The number of stringers you need is a function of the width of the
staircase and the tread material. Cut stringers can be spaced no
more than 18 inches on center, so a 3-foot-wide staircase needs
three stringers, and a set of slightly wider stairs (say 3 feet 6
inches) needs four stringers. The maximum 18-inch spacing presumes
treads of 5/4-inch wood decking or 2-by stock. When using synthetic
decking for treads, consult the decking manufacturer's instructions
- many require stringers be spaced no farther apart than 12 inches
or 10 inches, and some even require spacing as close as 8 inches.
Pay attention to the manufacturer's installation instructions. They
are referenced by the IRC in sections R317.4 and R317.4.1 and must
be followed for code compliance.
I've seen more than a dozen different methods used to mount stairs
to the deck frame, from blocks nailed to the framing between the
stringers, to toenailed stringers and stringers notched onto a
joist hanger. Most would not pass muster with an engineer or a
strict enforcement of the code.
I've become more conservative with age, and I worry about the
long-term performance of critical attachments on decks. IRC section
R311.5.1 states, "Attachment shall not be accomplished by use of
toenails or nails subject to withdrawal," referring to stairs,
decks, and other building elements. Because of the complex forces
on a set of stairs, I consider any nails - in just about any
arrangement - to be subject to withdrawal when used to mount the
head of a set of stairs.
Consequently, to provide positive attachment between the stringer
head and the deck frame, I like to use metal hardware. For a number
of years I used variable-slope rafter hardware, but now I use LSC
stair stringer connectors (Simpson Strong-Tie Co.; 800/999-5099,
made for the application (Figure 11). To avoid any issue with nails
pulling out of the deck frame, I secure the connectors with
metal-connector screws made by Simpson for the purpose. At less
than $2 each, these connectors are inexpensive insurance. And I
believe as more building officials read the code book more
carefully and learn about the hardware solutions, they'll be
red-tagging a lot of old-school stair mounting practices.
Figure 11. Relatively new stringer mounting
hardware is designed for simple and secure staircase hanging
without an engineer's design.
I mount stair stringers directly to 2x12 rim joists or to a header
set directly beneath 2x8 or 2x10 rim joists. Only a 2x12 rim joist
has enough depth to fasten the stringer hardware to it and provide
enough height for the last riser (Figure 12). The rim joist must be
able to support the additional load of the stairs. Neither the IRC
nor the DCA 6 provides much in the way of design guidelines for
when joists or beams support point loads such as a stair. It's
possible that simply doubling or tripling the joist would be
adequate, but without an engineer's evaluation, you won't know for
Figure 12. Only rim joists made with 2x12s (or
bigger) provide enough attachment surface for use with stringer
When I'm unsure of the ability of a 2x12 rim joist on a deck with
2x8 or 2x10 framing to support the load from the stairs, I provide
independent support by installing a single-ply header directly
beneath the rim joist. The header is screwed to 4x4 posts and bears
on 2x4s that are screwed to the 4x4s below the header.
Alternatively, I use notched 6x6s instead of 4x4s (Figure
Figure 13. The author installs a structural
header and support posts for the stair. The posts continue through
the deck frame to support the guardrail system.
When I mount stairs to the rim joist that closes off the end of the
floor joists, I use Simpson Strong-Tie DTT2Z Deck Tension Tie
hardware to secure the rim to the joists near the two outside
stringers. Stairs that attach to the rim joist at the outside edge
of a deck will probably overload the joist. Often those joists will
need to be doubled or tripled to support the additional load of the
The DTT2Z hardware can be bent at either of the two sets of side
notches; choose the bend location based on whether you want the
side flanges to mount to the left or right side of the stringer.
The tall leg of the hardware mounts to the rim joist or header and
the short leg attaches to the bottom of the stringer. I orient the
hardware so the side flanges face to the inside edge of the outside
stringers - that way, no metal shows. The LSC hardware can be
installed with nails, but to avoid any concern about "nails subject
to withdrawal," I use #9 x 1 1/2-inch Simpson Strong-Drive (SD)
Screws (Figure 14).
Figure 14. Use structural screws instead of
nails to mount the stringer hardware. Screws are less likely to
withdraw from the rim joist or header over time.
Know the Nose
Stair treads must have a nose projection of between 3/4 inch and 1
1/4 inches beyond the riser face when the tread cuts are less than
11 inches deep. (Stairs with open risers are exempt from the
overhang requirement.) This conveniently works out when the tread
cut is the code-minimum 10 inches, and the tread is a dry 2x12 or a
pair of 5 1/2-inch decking boards. Using either material results in
an overhang of 1 1/4 inches.
Figure 15. The open riser area must be closed down
to less than 4 inches on staircases that are more than 30 inches
above grade. Here the author installs ripped blocks beneath the
tread above, leaving partially open risers.
One more "gotcha" to watch out for when finishing up a set of
stairs is the riser opening. Simple sets of stairs often have open
risers; that is, there is no solid riser board. Living in an area
that gets an annual average of 5 feet of snow, I can attest to the
advantage of open risers when shoveling snow off stairs. But the
IRC limits the riser opening to less than 4 inches when the total
rise from grade to the top of the deck is greater than 30 inches.
When the stair is higher than the 30-inch limit and the design
doesn't call for finished closed risers, I install ripped 2-by
blocks between the stringers to close the riser opening down to 3
3/4 inches - closed enough for code compliance and still open
enough for pushing snow through (Figure 15).
Mike Guertin is a builder from East Greenwich,
R.I., and presents deck building clinics at DeckExpo and