I prefer to build stairs using housed stringers, which means
that the ends of the treads and risers are wedged and glued
into mortises routed into the stringers. While this approach
sounds like a lot of work, it doesn't take much longer than
crafting a decent set of notched-stringer stairs. What you get
for the extra effort is a stronger stair, since you haven't
notched away half the stringer, and one that's practically
While I first used this technique to build interior stairs, I
particularly like it for exterior ones. The tight, glued joints
at the stringer tend to keep out water, and I pitch the stairs
about 1/8 inch per foot of run to prevent water from puddling.
Stairs built this way stand up to the weather without the
cupping and cracking common to most porch or deck stairs. And
because each riser acts as a beam supporting the tread above,
I've never felt the need for more than two stringers. I've
built porch stairs that were 8 feet wide using just two housed
Preparing the Stock
You can use any rot-resistant material for exterior stairs. For
the project shown on these pages, I chose relatively cheap
pressure-treated 2x12s for the treads, since they would be
painted to match my client's painted porch floor. The stringers
(which would also be painted) are treated 2x10s; because they
remain mostly intact, they're actually much stronger than
notched 2x12s. I used 4/4 meranti — a fairly
rot-resistant tropical hardwood that's readily available in my
area — for the risers, in part because PT stock isn't
available in the 1x8 or 1x10 sizes that I needed. In addition,
meranti risers clear-finished with a Penofin penetrating oil
finish (707/462-3023, www.penofin.com) would nicely match the
meranti porch railing that I'd already made for the deck.
When I'm building a set of stairs, I select the best stock I
can, checking for knots, digs, and pitch pockets and cutting
out as many defects as possible. I pay close attention to the
bows and crowns in all the stringer, riser, and tread stock. In
every case, any crown faces up. Additionally, when I lay out
the stringers, I make sure that the bows in them will face each
other. That way, the bows more or less cancel each other out,
resulting in a straight, square stair.
After cutting the treads and risers to length, I rip them to
width. To straighten the edges, I like to rip both sides of the
stock. These treads are 11 inches wide, which, with a 1
1/4-inch overhang, gives me a run of 9 3/4 inches. After
ripping the treads, I bullnose them with a 3/8-inch roundover
bit. This bullnose perfectly matches the radius left at the
front of the mortise by the 3/4-inch-diameter bit I use to hog
out the mortises. I rip the risers to the stair rise of 7 1/2
inches, except for the bottom one, which has to be one tread
thickness — 1 1/2 inches — narrower.
Laying Out the Stringers
There are two main differences between laying out
housed-stringer stairs and notched-stringer stairs. Unlike
notched stringers, housed stringers are laid out from the
bottom edge of the stringer. And instead of marking the bottom
of the tread and the back of the riser, the layout marks you
make for housed stringers represent the top of the tread and
the front of the riser (see Figure 1).
After laying out the stringers, the
author makes a plywood jig to guide the pattern routing bit he
will use to cut the mortises for the treads and
I set stair gauges on my framing square exactly as if I were
going to notch the stringers, with one gauge on the 93/4-inch
run and one on the 7 1/2-inch rise. Working from the bottom, I
lay the square on the stringer, mark the run line, then remove
the gauges and shift the square forward along this line by
about 2 inches. Holding the square exactly on this line, I
reset the gauges, then lay out the first riser and tread.
As I move the square down the stringer to lay out the rest of
the treads and risers, I align the original 9 3/4-inch run
length on the square with the riser line I've just marked; if
I'm moving up the stringer, the original 7 1/2-inch riser
height on the square lines up with the tread I've just
When all the treads and risers are laid out, I mark the top and
bottom cuts. The top cut is one riser thickness behind the face
of the top riser. I like to make the bottom plumb cut about
half the thickness of the newel beyond the bottom tread
Starting at the back-of-the-tread/bottom-of-the-riser
intersections, I use a square to transfer index marks to the
second stringer. When laying out the second stringer, be sure
that those same tread and riser intersections align with the
index marks. You may have to fudge one or two by as much as 1/8
inch, but as long as you stay within that tolerance, the
stringers will be consistent and your stair will be square.
Fudging the layout in this way may require you to plane some of
the treads for an exact fit.
Because more than half the stringer will be visible to anyone
walking up the stairs, I pay attention to knots and the like.
Simply shifting the layout 6 inches one way or the other can
place wood defects behind the treads and risers, making a piece
of #2 material look like #1.
Cutting the Mortises
You don't need a lot of specialized tools to build a set of
To cut tread and riser housings, I use my old 2 1/2-hp Bosch
plunge router (anything smaller would be straining) with a
pattern routing bit (I use a CMT 811.690.11B) guided by a jig I
make from plywood scraps. I use a Kreg pocket screw guide to
help me fasten everything together (Kreg Tool Co.,
A simple jig. The key to housed
stringer stairs is the jig and a pattern routing bit. To match
the 1-inch depth of the available pattern routing bits, I make
my jig 1 inch thick by gluing up two 16-inch-by-20-inch
thicknesses of void-free 1/2-inch plywood.
I mark the cutouts in the jig several inches longer than any
stair layout I'll ever make, since they have to be long enough
for the mortises to extend through the bottom of the stringer,
and any extra opening beyond the bottom of the stringer helps
in clearing chips. It's okay to make the jig larger, but don't
make it any smaller, or the clamps used to hold the jig in
place will get in the way of the router.
When I cut out the opening, I plunge cut with a circular saw
and finish up with either a jigsaw or hand saw (Figure 2).
Since this jig will guide the router bit, any flaws in the cuts
will show up in the mortises, so I cut carefully.
Figure 2.Because the site-built jig will guide the
router, it's important to cut the template carefully. Here, a
carpenter makes the first plunge cuts with a circular saw
(left) and then finishes up with a jigsaw (right).
Rout in a clockwise direction. I
clamp the jig to the stringer so that the top of the tread and
the front of the riser align with the layout marks. The tread
nosing, of course, sticks out past the riser mark. Using a
3/4-inch-diameter pattern routing bit, I cut 1/2-inch-deep
mortises in two passes, making sure that the bit is lowered
enough that the bearing rides on the jig. (If the bearing
doesn't ride on the jig, the bit will cut into it.) To minimize
any chance of nicking the jig, I lower the bit into the jig
beyond the stringer before starting the router (Figure
Figure 3.Using a plunge router with a
3/4-inch-diameter pattern routing bit, the carpenter cuts
1/2-inch-deep mortises in two passes. The jig is clamped to the
stringer so that the top of the tread and the front of the
riser align with the layout marks.
With such a large bit buried in a tough southern yellow pine
stringer, feed direction is critical. I move the router
clockwise so that I don't jam the router by climb cutting, and
stop when necessary to clear chips. To avoid tear-out where the
back of the tread meets the front of the riser, the routing
passes are made working from the top to the bottom of the right
stringer and in the opposite direction on the left
After cutting the mortises, I make the top and bottom cuts in
each stringer with a circular saw.
Assembling the Stair
Before putting the stair together, I cut wedges from
9-inch-long scrap riser material with a miter saw. The wedges
are beveled at 4 degrees, which is done by setting the chop saw
to 2 degrees, then flipping the stock end-for-end at each cut.
I eyeball the cuts so that the sharp ends of the wedges measure
about 3/16 inch, and cut two for each tread and riser (Figure
4). A word of caution: Don't cut too many wedges from each
piece of stock; to keep your fingers intact, throw away at
least 3 inches of each block.
Figure 4.Cut from 9-inch-long scrap riser
material, the wedges are beveled at 4 degrees, which is done by
setting the saw to 2 degrees and flipping the stock end-for-end
at each cut. The carpenter eyeballs the cuts so that the sharp
ends of the wedges measure about 3/16 inch.
Next I set the stringers upside down on horses and firmly seat
the top and bottom treads in their mortises with their crowns
facing up. Then I check that the back of each tread aligns with
the riser cut above ("above" and "below" in this case refer to
the orientation of the stair once it's installed). If the
tread's too wide, I plane it down to fit. With the tread seated
and the stringers bar-clamped together, I drive home a heavily
glued wedge on each side, stopping when the end of the wedge
starts to splinter (Figure 5). If the wedge has intruded into
the riser mortise below, I chop off the intrusion with a
chisel. For glue, I prefer to use Titebond III (Franklin
International, 800/669-4583, www.titebond.com), which is rated for
outdoor use, but PL 400 (OSI Sealants, 800/999-8920,
www.stickwithpl.com) or a polyurethane glue
would work, too.
Figure 5.With the tread seated and the stringers
bar-clamped together, the carpenter drives home a heavily glued
wedge on each side.
After I've set the top and bottom treads, I check for square by
measuring the stair's diagonals. If the treads are squarely
cut, the stair should be dead on. If it's off a bit, I adjust
the stringers to get the diagonals even. Then I set and wedge
the rest of the treads, cutting back any wedges that extend
beyond their tread with a handsaw.
Gluing sequence is important. When
placing the risers, I make sure that any crown faces the tread
above. First, I run a bead of glue along a riser top, then
quickly seat it in its mortises so that it contacts the tread
above. This smears the glue around, and helps prevent
Then I pull the riser away from the tread below and run a bead
of glue along the back of that tread before sliding the riser
back into position (Figure 6). Finally, I liberally apply glue
to a pair of wedges and smack home a wedge on each side of the
riser, occasionally tapping the riser to keep it seated against
the tread above.
Figure 6.To set a riser, the carpenter runs a bead
of glue along its top, then seats it in its mortises so that it
contacts the tread above and smears the glue around, which
helps prevent drips (top). Then he runs a bead of glue along
the back of the tread before driving home wedges on each side
of the riser (bottom).
Screws complete the assembly. Using a Kreg jig, I
drill three pocket screw holes into the top of each riser.
Epoxy-coated 1 5/8-inch deck screws driven here pull the tread
and riser snugly together, and help ensure a sound glue joint.
Using the Kreg pocket screw bit (any countersink bit would
work, but this one's handy), I then predrill for 2 1/2-inch
stainless steel screws into the back of the tread below (Figure
7). As soon as the last riser is in, I flip the stairs over so
that I can scrape off any glue drips.
Figure 7.Using a Kreg jig, the carpenter drills
three pocket screw holes into the top of the riser, then uses
epoxy coated 1 5/8-inch deck screws to pull the tread and riser
together (left). Next he predrills (right) before driving 2
1/2-inch stainless steel screws through each riser into the
back of the tread below.
Setting the stairs is a piece of cake. Two or three guys can
move them into position, and half a dozen screws into the top
riser secures them.Andy Engelis a carpenter and writer in Roxbury,