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Deck
Details:
Building Tall Stairs
For A Second-Floor Deck
Part 1 of
2
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| In
This Article:
After some careful planning
and CAD design:
- A part of the original
deck railing is removed.
- The deck platform is
extended.
- New supporting posts are
installed for the extension and the stair stringers.
- The stringers and treads
are installed.
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Related
Articles:
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| Skill Level:
3-4 (Intermediate to Advanced) |
Time Taken:
About 3 Days |
By
Bruce W. Maki,
Editor
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The owners of this house in Northern
Michigan wanted to be able to reach their deck without
going through the house. |
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| The deck surface is just over 10 feet
above the ground.
Note pavement below the deck. This complicated the
digging of the post holes.
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After some discussions with the
homeowners, we decided that this corner of the deck
would be the best location for the stairs. |
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| A view of the underside. Note how the deck
joists rest on a double-2x10 "beam" that is
bolted to the posts. |
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|
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I began by removing a short section of
handrail spindles. |
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| I marked the rim joist where I planned to
cut. This is the left edge of the fourth joist (red
arrow).
There will be a new joist fastened to the side of
this one.
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|
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I cut the 2x8 rim joist with a
reciprocating saw. |
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| Then I hammered and pried off the 4-foot
piece of rim joist.
Note how the deck board above has been pried up
so the nails would pull out of the rim joist. |
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|
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I needed to remove the corner newel
post, so I pried the handrail boards away from the
post. |
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| Then I cut the nails with a reciprocating
saw and the post fell right out. |
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|
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I installed the first extended 2x8 joist.
I clamped this board to the outside joist and also to
the deck board above, to pull it up tight against the
original deck surface. |
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| Then I installed another extendo-joist
next to the fourth original joist. |
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As you can see, the new joist extends
behind the "beam".
But getting this joist into place wasn't easy... the
bottom of the 2x8 hit the beam. The old joists had
shrunk a bit, so I had to trim about 1/8" from a
short stretch of the bottom of this new joist. |
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| I inserted the middle two joists, but did not
attach them.
I also added a filler strip to the outside of the
first joist. |
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|
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I started attaching the new rim joist, but
there was a small problem. The double joist on the left
was twisted.
Since I had no helpers on this job, I clamped a scrap
of 2x4 (red arrow) to a joist to support the weight of
the rim joist.
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Fixing Twisted Lumber:
I intentionally installed this rim joist on a slight
angle.
Since the middle joists were not attached yet, they
sagged a bit. This allowed the rim joist to sag
downward as the right-hand end rested on my
temporary support block. Luckily, the sag was just
enough, so the rim joist was perfectly aligned with
the side of warped double-joists.
Then I drove 6 deck screws into the left hand
end of the rim joist, to connect it to the double-joist. |
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|
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I raised the right-hand end of the rim
joist by squeezing the mis-aligned joists with a
Quick-Grip clamp.
This caused the twisted double-joist to straighten
out. Since the "lever arm" is 4 feet long,
it's easy to twist another joist (or two) into
compliance. |
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| I fastened the middle two joists. First I
drove screws through the rim joist into the ends of the
middle joists, then I clamped them to the existing joists and
fastened them with 3" deck screws and 10d
galvanized nails. |
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|
Supporting Structure:
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I set the deck support posts into place
and clamped them to the deck joists. |
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| Then I adjusted them until they were
plumb. |
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Post Holes -
Cutting Through Asphalt:
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I used a can of landscape spray paint
to mark the centerlines of the posts, and the hole to be
cut in the driveway. |
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| I used a circular saw with a diamond blade
to cut the asphalt driveway. |
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|
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I used a rotary hammer to chip away a
corner of the asphalt. I also tried a pick-ax, but it
sprayed too much debris in my face. |
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| Then I used a huge 4-foot long pry bar to
lift the chipped-out corner. The blacktop just popped
right out.
But... on some of the holes, I had to chip away the
asphalt with my rotary hammer and a chisel tip bit. It's
basically a mini-jackhammer. With an emphasis on mini.
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|
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I dug the post holes over 4 feet deep
with post-hole diggers. I also used a shovel and a
pointed pry bar for loosening the packed soil.
When the digging was complete, I compacted the
soil in the bottom of the hole, using a cast iron
tamper. A chunk of 4x4 also works.
|
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| I nailed a post anchor to the
bottom of the post. These are 10d galvanized nails
specially made for attaching framing connectors. |
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|
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I set the 14-foot-long post in the hole.
This was kinda awkward, since I had to slide the post
through the proper space between the deck joists.
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| At the top I clamped the post to the
joists.
Note that the post was too long (it only needed to be
as high as the deck joists). This was okay, since
cutting off a piece of excess post is much easier than
trying to estimate the post length beforehand.
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|
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Down below, I clamped a bar clamp to the
post while the post anchor was resting on the bottom of
the hole.
Then I lifted the post slightly and supported
the clamp on a pair of 2x4's. This kept the post anchor a
couple of inches above the bottom of the hole, which
is necessary for the concrete to properly surround the
curved metal tabs.
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| I screwed the cross-boards to the post. I
kept knocking the posts out-of-plumb, but I'll have
plenty of opportunity to re-plumb the posts after I pour
concrete into the holes. |
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|
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I poured concrete in the post holes,
making sure the concrete almost reached the bottom of
the wood post. I used one 80 pound bag of Quick-Crete
for two posts. |
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Stringers:
| I cut the stringers. Since I started with
a simple QuickCad drawing, I was able to easily get
accurate stringer dimensions. I would never
approach stair construction without CAD software.
Cutting stair stringers is a subject for an entire
article. You can read this
article about cutting short deck stair stringers.
These 16-foot long stringers used the same layout and
design techniques... there are just more notches.
|
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|
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I added this extra piece of 2x8 (red
arrow) below the joists. The top of the stair stringers
will rest against this board. |
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| To support this "back board", I
screwed some 2x4 blocks behind the joist. |
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|
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I set the outer stringers in place to help
lay out the location of the two bottom posts. At this step it was very important to make sure the
stringers were parallel to the original deck.
|
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| I set a 4x4 in place and marked the center
lines with landscape spray paint. |
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|
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I attached some blocks of 2x8 to the
backer-board. The tops of the stringers will be fastened
to the sides of these blocks. |
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| The holes for the lower handrail posts
were dug. |
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|
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The outer stringers were set in place
against the top fastening blocks. |
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| I clamped the top of the stringer to the
2x8 block and drove in a few 3" deck screws. |
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|
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We adjusted the lower ends of the stringer
until everything was level (not a simple task), then
attached the ends of each stringer to a temporary
support board. |
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We placed two 8-foot 4x4 posts in the
holes (with metal anchors attached to the bottom ends)
and secured them so the anchors were a couple of
inches above the dirt.
- We adjusted the posts until they were reasonably
plumb.
- We made sure the stringers were still in good
parallel alignment with the main deck.
- We poured concrete into the holes to surround the
metal anchors.
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|
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After the concrete had hardened, I
back-filled the holes part way.
I cut out another section of pavement so I could
attach a 4x6 beam to the posts, to support the
middle two stair stringers. |
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| To properly support the middle two
stringers, I fastened this piece of 4x6 (red arrow) to the posts,
just below the outer stringers. This was difficult to fasten because I could barely
get my drill/driver into the hole to drive some lag
screws through the post into the 4x6 beam. I also
added some metal angle brackets with galvanized nails
for extra fastening power.
|
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|
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I dug two more holes and installed the middle
support posts.
These are mainly needed to support the handrail, but
they also stiffen the stair stringers
substantially.
I could have just used short posts to attach the
handrail to the stringers, but I wasn't sure if these
16-foot stringers would work without extra support in
the middle. I figured they would be strong enough, but
the building inspector said that the deflection had to
be less than L/240. Since L (the length of the
structural member) was 192 inches, that gave me an
acceptable deflection more than 3/4 of an inch. While
that might be acceptable with the building codes, I
wanted the stairs to be less springy, so I opted to
extend the handrail posts all the way into the ground. |
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Like the other posts, these go 4 feet deep to prevent the frost
from heaving them during our frigid winters here in Northern
Michigan.
| I installed the middle stringers. |
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|
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These stringers are attached to the front
2x6 board, and also to the 4x6 beam.
I used some synthetic shims to support the middle
stringers and get them to the right height.
|
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| At the middle posts, I added a pair of 2x6
cross-members underneath the stringers. |
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|
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I used some small blocks of 4x4 (red
arrow) to attach the middle stringers to the
cross-members. |
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Tread Installation:
| I fastened the treads to the stringers.
This procedure needs to be done starting at the bottom
and working up, because the
nose of each front board overlaps the screws in the
board below, making it difficult to reach those
fasteners.
Also, the back tread board needs to be installed
before the front board.
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|
I always pre-drill holes for the screws at the ends of the
boards. While treated wood often won't split during construction
(because it has so much moisture in it) as the lumber dries out the
ends will split at the screw locations.
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I installed all 34 tread boards (for 17
steps) in about an hour and a half.
These treads were 42 inches long. I needed the extra
length so the opening between handrails would be at
least 36 inches, which is required by the building code.
This is a drawback of the wide handrail design used on
this deck.
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Some Final Details:
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When I poured concrete around the deck
posts, I had tacked some small pieces of expansion
joint material to the post.
I'm not sure that this extra feature is necessary. I
figure it falls into the category of "can't hurt,
might help". |
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I should have nailed this expansion joint material more
carefully, so the top edge was at the same level as the surrounding
pavement. That allows the expansion joint to be employed as a guide
to screed the concrete. But I was in too much of a hurry... I
just tacked this stuff in place as the homeowner poured the
concrete.
| I used a sharp knife to cut the expansion
joint back to ground level. It took repeated cuts to
slice all the way through. |
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|
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To supplement the strength of the deck
screws, I drove 16d nails at major load-bearing
connections.
Building inspectors (and building codes) require a
certain size of nail for many structural connections.
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The Finished Product:
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The view from far away. |
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| I was very pleased with the feeling of sturdiness
in this stair project. Adding the middle support posts
probably made a huge difference, and using 4 stringers
helped too.
If I had employed only 3 stringers, the spacing would
have been about 21 inches on center, which may let the
stair treads flex noticeably under load. Regular deck
boards should be supported at 16 inches on center, or
less. With 4 stringers, the spacing was about 14"
o.c., so the treads didn't flex at all. |
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|
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One problem with modifying an old deck is
the stark contrast between old and new materials.
A few days later I used a small 1200 PSI pressure
washer to clean the surfaces of the old deck and
handrail. After three hours of cleaning the old wood
looked much newer.
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Click
here to read Part
2 about installing
the handrails for this deck.
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Tools
Used:
- Cordless Drill/Driver
- Basic Carpentry Tools
- Circular Saw
- Reciprocating Saw
- Jig Saw
- Heavy-Duty ½" Drill
- Rotary Hammer
- Miter Saw
- Table Saw
- Belt Sander
- Bar Clamps
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Materials Used:
- Treated Lumber:
- 4x4 x 14' (2)
- 4x4 x 12' (2)
- 4x4 x 8' (4)
- 2x8 x 8' (7) (Joists,
Beams)
- 2x12 x 16' (4) (Stair
Stringers)
- 5/4x6 x 14' (8) (Stair
Treads)
- 5/4x6 x 8' (5) (Decking)
- 3" Deck-Mate Screws
(about 5 lb.)
- 2½" Deck-Mate Screws
(about 10 lb.)
- 16d Galvanized Nails
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