Last year I got a call from a client who wanted to create more
outdoor living space by building a deck along the back of her
house over a part of the yard that was too steep to use. She
said she wanted to use Trex, so I was picturing a conventional
deck and guardrail. But when I stopped by her house —
which was located in the hills above Oakland, Calif. — to
look at the job, it became apparent that a conventional design
was not going to work.
For one thing, the house had spectacular views of the bay and
of San Francisco — views that a wood-picket guardrail
would block. Therefore, I suggested using a glass or cable rail
Also, one end of the deck would lap onto an existing
salt-finish concrete patio; in passing, the owner mentioned
that she didn't like the surface of the patio and wondered if
it would be possible to cover it with the same composite
material we used on the deck. I suggested covering the patio
with stone tile instead, and when she said she liked that idea
I proposed putting the same material on the deck, too; that
way, the two surfaces would match.
By the end of our meeting, the client had agreed to have my
company cover the existing patio with slate tile and build a
slate-covered wood-framed deck with a glass guardrail system.
The deck would be accessed from the patio, the existing kitchen
door, and new French doors in the dining room wall.
I would have preferred to build a freestanding deck and avoid
having to deal with a ledger, but there was fill along the
foundation so we couldn't have installed piers there without
digging deep holes. Normally we only have to excavate to
undisturbed soil, because in this area the temperature almost
never drops below freezing.
Our plan was to use a 4-by beam for the ledger, connect a
portion of it to the house, and pick up the other end with a
post on a concrete pier just beyond the end of the building.
The framing at the other edges would land on posts, concrete
piers, or the existing concrete patio (see Figure 1).
Figure 1. The joists run between a 4x10
ledger beam and a 4x12 outer beam carried by posts on concrete
piers (top). One end of the deck laps about 5 feet onto an
existing concrete patio (bottom).
Concrete piers. There were seven
piers in all, each 2 feet square and about 15 inches thick, and
each reinforced with four pieces of #4 rebar. Before placing
the concrete, we positioned Simpson CB44HDG (hot-dip
galvanized) column bases in the piers to hold the 4x4 posts.
Since we were framing the deck with pressure-treated Douglas
fir (ACQ) and the new chemicals are so corrosive, we made sure
all the metal connectors were hot-dip galvanized or approved
for use with ACQ.
Slope. Most decks slope away from the
house so that water will drain off the outboard edge. But in
this case the continuous glass rail presented a barrier, so we
sloped the deck toward the house and allowed it to drain
through a 3/4-inch space between the deck and wall. We
installed a gutter below the deck to catch this water and
direct it away from the foundation (Figure 2).
Figure 2. Since a continuous glass
handrail will prevent water from draining off the outer edge of
the deck, the author sloped the joists toward the house (top)
and used stacks of 3-inch-square washers to space the ledger
beam off the wall (middle). Water drains through this space and
is collected by a gutter below the deck (bottom).
The slope presented a challenge because the structural
glass-rail system needed to be in continuous contact with the
perimeter beams. Sloping the end beam would have meant sloping
the rail (which would look bad) or complicating the
installation by requiring the glazing contractor to taper some
of the glass panels. To avoid those scenarios, we installed the
end beam level and allowed the joists to drop down from it at
the end closest to the house. This created a small step at the
bottom of one of the rails, which we later trimmed with strips
Since we wanted to retain an existing downspout from the roof,
we blocked the 4x10 ledger beam an extra 3 1/2 inches off the
wall to allow the downspout to pass through. We used LedgerLok
screws (FastenMaster, 800/518-3569,
www.fastenmaster.com) to attach two lengths
of 4x10 to the back of the ledger, leaving a gap for the
Wall connection detail. The usual way
to fasten a deck ledger is to bolt it to the rim joist of the
house. But on this house the joists cantilevered a short
distance beyond the foundation wall so that we couldn't fasten
to the rim, which was supported only by nails. Instead, we used
Simpson HD2A hold-down hardware to attach the ledger to the
floor joists beyond the rim — a connection detail similar
to one an engineer had specified on an addition I'd
To gain access to the joists, we cut an opening through the
stucco on the bottom side of the overhang; later we covered
this opening with an access panel so that the connection could
be inspected and maintained.
We staggered the bolts high and low through the beam and
connected it at seven locations. Each hold-down was
through-bolted to a joist and tied to the beam with 5/8-inch
galvanized threaded rod (Figure 3).
Figure 3. The left end of the ledger beam
(top) is bolted to the house with 5/8-inch all-thread that runs
between nuts and washers outside and Simpson HD2A hold-downs
inside (bottom). This ties the ledger to the joists instead of
to the rim — which, because the joists are cantilevered,
is not supported by a sill.
To prevent leaks, we filled the holes through the stucco and
the rim with Sikaflex-1a sealant (Sika Corp., 800/933-7452,
www.sikaconstruction.com) before installing
the rod. And to provide drainage we spaced the deck about 3/4
inch off the building by placing stacks of square 3-inch
galvanized washers over the rods between the stucco and the
Outboard edges. The left end of the
deck lapped onto and was supported by the patio. We framed the
two outboard edges of the deck with 4x12 beams, partly to
support the load but also to make sure we had something solid
to bolt the rail to.
We provided lateral strength by cross-bracing the end of the
deck with 4x6 timbers. We installed them in line with the posts
and beam because that method is stronger and looks better than
lapping the pieces (Figure 4).
Figure 4.The author cross-braced
the end of the deck with 4x6 diagonals (top), which he fastened
to the corner posts with the same bolts that hold the posts in
the column bases (middle). The diagonals butt to a post at
midspan and are bolted to it through the same Simpson CC44
column cap that connects the post to the beam above
Joists and sheathing. Once the perimeter framing was in place,
we installed 2x10 pressure-treated Douglas fir joists 16 inches
on-center, blocked midspan and supported by Simpson ZMAX joist
hangers. We then sheathed the deck with a double layer of
3/4-inch T&G pressure-treated plywood glued and nailed to
the framing. The added layer provides the stiffness necessary
to prevent natural stone tile from cracking. Had we been using
ceramic tile, a single layer over our 16-inch joist spacing
would have sufficed.
An important aspect of this project was choosing a method to
apply the stone that would reduce the likelihood of cracking
caused by deflection or movement of the deck or slab. The
proper way to do this is to install the stone (or tile) over a
crack-isolation membrane. Also referred to as antifracture or
uncoupling membranes, these materials are designed to reduce
the amount of stress that can be transferred from the substrate
to the finish. (For a list of available crack-isolation
membranes, visit the Tile Council of North America Web site at