Readers of this magazine likely know how to safely secure a deck
ledger to most houses. But what about the oddball situations? Can
you attach a ledger to a concrete wall? What about to masonry
veneer, stucco, EIFS, logs, SIPs, I-joists, or cantilevered floor
framing? The answer is often nuanced, but sometimes it's a flat-out
And it's not just the mechanical attachment that makes for a safe,
durable deck. "Flashing is as critical as the original design,"
notes Frank Woeste, P.E., Ph.D., professor emeritus at Virginia
Tech. Poorly detailed flashing or flashing (such as aluminum) that
corrodes in short order when in contact with ACQ preservatives lets
in water that rots the house framing. It doesn't matter how many
bolts you use to attach the ledger if the house framing it's
attached to rots away.
The advent of engineered floor systems also brought about some
unanticipated (by carpenters, anyway) structural issues. As
reported in the July/August 2007 issue of Professional Deck Builder
(Decking News, "Siding Hides Warning Signs of Deck Collapse"), some
early engineered floors used only 3/4-inch OSB as a rim board.
Compound that with poor flashing, and you've got a recipe for
The details shown here are intended as guidelines; other solutions,
good and bad, exist. And if you have any doubt at all, it's never a
bad idea to pay for an engineer's expertise.
Masonry walls? It depends.
Direct attachment to solid masonry — poured concrete or
grout-filled block — and concrete block is fairly simple.
Details for doing so are widely available; the ones shown here
(Figure 1) are from Virginia's code. For solid masonry, steel
expansion anchors whose bolts are a minimum of 1/2 inch in diameter
and penetrate the masonry by at least 2 1/2 inches can take the
place of lag bolts. The anchor spacing would be as shown at right
in the table "Ledger Fastener Spacing for Masonry Walls."
Figure 1. In most cases, deck ledgers can be
bolted directly to poured concrete or concrete block walls.
Expansion anchors — never lead shields — are used in
solid masonry or filled block, and approved epoxy or acrylic
anchors and bolts are used in hollow masonry.
Note that I'm talking about structural masonry here, and not
masonry veneer. Attachment to masonry veneer is a bad idea, and the
reason that's so is discussed on page 6.
There is a potential problem with attaching a ledger to concrete,
which Woeste says should trigger a building department to require
an engineer's design: "Although the strength of some expansion
anchor bolts is rated, the strength of the concrete into which
they're placed is probably not known in practice."
When attaching a ledger to hollow masonry block, use adhesive
anchors, such as the Epcon A7 from ITW Red Head (800/348-3231,
www.itw-redhead.com) or the Hilti HIT HY 20 system
(866/445-8827, www.us.hilti.com). The threaded rod used with the
anchors must be at least 1/2 inch in diameter and must penetrate
the block by at least 3 1/2 inches.
The anchors used for this application are pouches made from plastic
or stainless steel screen. They're filled with a special adhesive,
inserted into a hole drilled (without using the impact feature of a
hammer drill) in the block, and held in place with a tab. The
threaded rod is inserted in the adhesive, which is allowed to set
up according to the manufacturer's instructions before the ledger
is installed. Be prepared for sticker shock — the adhesive
anchors can cost upward of $40 per hole.
While there's no flashing called for when joining a ledger to
masonry, it's recommended that the top of the ledger be caulked to
the wall to keep out water. And don't be cheap here: Buy a
high-quality caulk. It's all that's keeping water off the fasteners
holding the deck up, and this is the only chance anyone will ever
have to seal this joint.
Finally, when you're going to attach the joist hangers to a ledger
installed on masonry, remember to order the 1 1/2-inch hanger
Insulating concrete forms?
Forethought pays off when dealing with ICFs. To attach a ledger to
an ICF wall, the IRC calls for direct concrete-to-wood contact,
which is usually accomplished with "anchor tunnels." These plastic
inserts thread into 6-inch-diameter holes drilled in the foam forms
(Figure 2). Each tunnel holds an anchor bolt in its center, keeping
it square to the wall as the concrete fills the tunnel during the
pouring of the wall. Anchor tunnels are installed at a
code-prescribed spacing, which varies with the floor loading and
span, and they're staggered above and below the centerline of the
ledger so as not to create a line that's likely to split the
Figure 2. Plan ahead to attach to ICFs. A
plastic anchor tunnel screws into a hole drilled in the ICF. The
tunnel holds an anchor bolt square to the wall, and the concrete is
poured around it. Tunnels are installed in a staggered line to
minimize forces that might split the ledger.
But what do you do when the deck is an afterthought? Jim Eggert, a
design-build contractor in Branford, Conn., specializes in ICF
construction. He's supported ledgers on 5/8-inch or 3/4-inch
stainless steel threaded rod that's epoxied into holes drilled in
the ICFs. Eggert claims that these thicker rods can offer a bending
moment that's sufficient to bridge the thickness of the foam in an
ICF wall. Most jurisdictions would require an engineer's stamp of
approval on such an assembly, however.
Traditional stucco? Sure, but flashing can be
In theory, attaching a ledger to a traditional stucco wall is
pretty straightforward. But while it might be tempting to simply
bolt the ledger through the stucco, such an attachment won't meet
the requirements in the 2007 IRC Supplement (see Professional Deck
Builder, "New Ledger Attachment Requirements Adopted," Jul/Aug 07).
The ledger must be bolted to the framing because the stucco isn't
structural and you'd be imposing shear loads on the bolts that
aren't accounted for in the code tables.
To attach the ledger, you have to cut the stucco back to the
framing with a masonry saw, which should be set deep enough to
sever any wire lath underlying the stucco. This is easy enough to
do if the stucco guys achieved a uniform thickness. The next trick
is to slip a piece of flashing (galvanized steel would be the best
choice, to be compatible with the steel wire lath) about 3 inches
up under the building paper that should underlie the stucco. If
you're very lucky, there won't be any nails holding the lath in
place for those 3 inches.
I wouldn't be so lucky and would expect to spend some time cutting
nails with a hacksaw blade or with a long metal cutting blade in a
recip saw. I would double-flash such a ledger, as well as extend
the bottom cut in the stucco an additional 3 inches to allow for
flashing to extend beyond the edge of the ledger (Figure 3).
Figure 3. A masonry saw cuts out the stucco
and lath. The bottom cut extends about 3 inches to the sides so
that flashing can be extended beyond the ledger.
Engineered floors? Maybe.
By engineered floors, I'm talking about I-joists and open-web
joists. The considerations are different for the two.
Whether or not a deck can be attached to an I-joist floor depends
on the material used for the rim board. If it's an I-joist or
plywood, forget it — unless you can convince an engineer to
sign off on the detail. But if the rim is 1 1/8-inch LSL or 1
1/4-inch LVL, and the manufacturer lists that as appropriate for
attaching a deck, then go right ahead (Figure 4). On an existing
house, it's important to field-verify the rim-board material before
bidding the job.
Figure 4. Ledger attachment to an I-joist
floor depends on the rim-board material. If it's 1 1/4-inch LVL or
1 1/8-inch LSL — and the manufacturer approves — ledger
attachment proceeds typically. Watch out for thin plywood or
I-joists used as rim board.
Watch out, too, when you turn the corner. It's pretty common for
the rim board running perpendicular to the joists to be LVL or LSL,
while the end joist that parallels the other joists is just another
I-joist. If that's the case, your engineer would need to detail the
ledger attachment to that side of the house — or that portion
of the deck would have to be freestanding.
Open-web floor trusses are another question. Codes in some areas
outright forbid attaching a ledger to open-web floor trusses. Such
floor systems are inherently engineered, and adding a load outside
of the design's parameters can have unexpected consequences.
However, Ron Strohbeck, a truss designer in Carlinville, Ill.,
notes, "Most truss manufacturers allow ledgers to be bolted to
floor truss systems." But he advises, "Check with them first and
check with the building department." This is definitely not a
liability I'd take on without heeding Strohbeck's advice.
Log walls? Yes, with
If you've ever worked on a log home, you know that it brings some
interesting challenges to the table. The walls aren't flat, for
one, and to really grab your attention, you can count on them
shrinking in height by as much as a foot, if green logs were used.
Even so, veteran contributor Kim Katwijk, a deck builder in
Olympia, Wash., says, "Logs are pretty easy."
Katwijk explains that how you attach a ledger depends on the size
and design of the logs: "West Coast logs tend to be big, say 18
inches in diameter, and there's a large trough between them." When
the ledger needs to go in this space, Katwijk bridges the gap to
create a reasonably flat surface with a horizontal 2x6 (Figure 5)
or by custom-tapering a 4x6 for very long logs, which can vary in
width. The ledger is then attached to the face of this horizontal
Figure 5. Logs aren't flat and can't be
effectively flashed. Bridging the space between the logs with
either a horizontal 2-by member or vertical 2x6 standoffs makes a
flat surface. Engineering might be required, as these attachments
aren't described in the code.
It's pretty much impossible to flash a ledger to a log home. You
could cut a reglet (a slot meant to receive flashing) into the log
above the ledger, but Katwijk believes capillary action is as
likely to draw water in as the flashing is to keep it out. Instead,
he tapers the top of the ledger, so water will drain away from the
logs, and carefully installs the ledger so that no debris- and
water-trapping pockets are created. He caulks the top of the ledger
to the logs using a tripolymer caulk, inserting backer rod where
Another challenge is that logs settle as they shrink. New homes
built from standing dead timber shrink the least, according to
Katwijk, but they can still shrink several inches. The worst
situation is a second-floor deck on a new home made from green
logs. You can expect the supporting wall to shrink as much as a
foot. In both these cases, the posts holding up the outside of a
deck attached to a log home have to be made adjustable. Special
hardware (Figure 6) takes care of such shrinkage, and you'll need
to have it engineered. The log home supplier should be able to
provide an estimate of the amount of shrinkage to allow for.
Figure 6. Logs shrink; vertical posts don't.
Decks attached to new log homes have to accommodate the expected
shrinkage in the logs. Fabricated engineered post bases that allow
adjustment as the logs settle solve the problem.
One relatively simple approach to hanging a ledger on a log house
is to use a metal standoff (Figure 7). For example, the Maine Deck
Bracket (207/212-0888, www.deckbracket.com) is an aluminum standoff that's
bolted to the house at intervals determined by the joist span. A
double 2-by bolts to the brackets, and acts as a flush beam to
support the joists at the house. This leaves a generous drainage
space between the house and the deck, reducing the likelihood of
Figure 7. The Maine Deck Bracket is an option
that works well on log homes.
Cantilevered floors? No (but sometimes they
can be framed around).
Attaching a ledger to cantilevered floor framing is generally
forbidden by code — for good reason. Often, a cantilevered
floor is pushed to its maximum load-bearing capacity just by
supporting the existing loads. You can't know this without an
engineer's evaluation. And even if the joists have some unused
bearing capacity, it's likely that the band joist on the
cantilever, to which the deck ledger would be attached, is just
nailed into the end grain of the joists. That connection isn't
adequate to support a deck (see photo, top of article). The band
joist to which you typically attach a deck is supported directly by
the house foundation.
It's possible, but a lot of work, to pull the band joist off the
cantilever, and slide the deck joists under the cantilevered floor
to where they can bear on the house's top wall plate or mudsill.
The span design of these joists must take into account not only the
typical loads from the deck, but also the load now imposed by the
house floor, wall, and roof. And it's practically impossible to
prevent water from following the deck joists into the house and
rotting it out.
In fact, the first deck job I ever did was replacing such a deck,
as well as a good portion of the house's walls and interior
flooring. There were literally bushels of carpenter ants at work on
that house because of the moisture damage caused by the deck. I'd
avoid this approach like the plague.
If it's just a small cantilevered bay, then framing around it isn't
very hard. Doubled or tripled joists on either side of the bay can
carry a header, which in turn carries the framing beyond the
cantilever (Figure 8).
Figure 8. It's a code violation to attach a
ledger to either a chimney or a cantilever. Box framing around it
is the solution, up to about 6 feet. A larger box-out may be
permissible with engineering.
Don't even think about it.
Clearly, there are more ways of attaching a deck ledger to a wall
than are addressed even in the new ledger attachment section of the
2007 IRC Supplement. Nonetheless, there are situations where
attaching a ledger just isn't appropriate.
For example, attaching a deck ledger to masonry veneer — when
the brick or stone is applied over a framed wall — is a code
violation nearly everywhere. Masonry veneer is not designed to
transfer the loads imposed by a deck; the deck pulling away from
the house could also pull the masonry veneer away.
Structural insulated panels (SIPs) also present problems for
deck-ledger attachment. SIPs are a sandwich of OSB and rigid foam.
Typically, there will be a 2x6 member at each edge, and there may
or may not be more 2x6 studs running up the center. Although SIPs
can be used for stand-alone structures, they are also often used to
sheathe and insulate timber-framed homes.
While the 2x6s in the SIPS might seem to provide a good anchor for
lag bolts, the foam and OSB don't. Without engineering, the IRC has
no provision for attaching to SIPs. If the SIP wall rests on a
conventional floor system, however, you can attach to that floor as
you normally would.
EIFS, or synthetic stucco systems, make me nervous. Although the
new drainable systems are a dramatic improvement over the older
systems — which engendered a flurry of class-action lawsuits
in the 1990s — flashing and sealing EIFS is a job for a
Unless the deck ledger is in place when the stucco is applied, it's
best to avoid attaching a ledger to a building clad in synthetic
stucco. Penetrations to the stucco cladding are notorious for
allowing leaks, which the synthetic stucco doesn't allow to dry
out. The result will be rot and mold.
So, what's a deck builder to do?
Few of us want to turn down a job. Luckily, it's rarely necessary
to do so. On most houses where attaching a ledger is a problem,
there's probably a solution. "Almost all jurisdictions accept the
sealed design of a registered professional engineer in situations
that aren't described in the IRC," says Woeste. "An engineered
solution is a professional approach for the contractor, and most
important, it protects the client from an accident." Additionally,
from a contractor's point of view, an engineered design is a little
like buying an insurance policy. While you're still liable for the
construction of the deck, the engineer becomes responsible for
problems with the overall design.
And, of course, there's a simple solution to problematic
ledger-attachment situations: Don't use a ledger. Instead, build a
freestanding deck (Figure 9), which uses a carrying beam, posts,
and footings in place of the ledger. It's a good practice to set
this beam 2 or 3 feet away from the house, and cantilever the deck
the remaining distance.
Figure 9. Adding a beam near the house avoids
the need for a ledger attachment. The biggest issue is finding
undisturbed earth to support the footings close to the
Both Woeste and Katwijk advocate this approach, and Rhode Island
contractor Mike Guertin points out: "One of the main advantages to
building self-supporting decks is the little-used IRC provision
that exempts them from frost-depth footings. Sounds crazy, doesn't
it? Rhode Island's frost depth is 42 inches, and I absolutely love
the look on building inspectors' faces when they come for a footing
inspection and see I've dug down only 12 to 18 inches.
"I keep the code book handy: In the 2006 IRC, R403.1.4.1 exception
3 states, ‘Decks not supported by a dwelling need not be
provided with footings that extend below the frost line.' So the
only provision for footings that applies to freestanding decks is
in R403.1: ‘Footings shall be supported on undisturbed
natural soils or engineered fill.'"
Guertin goes on to say that finding undisturbed soil to support
deck footings in the backfilled area close to a new house can be a
dicey proposition. However, many building departments consider
backfilled soil to be undisturbed after five years. And to add
perspective, the worst thing likely to happen is that the deck
might settle, an annoying but slowly occurring problem. Woeste
notes, "To my knowledge, no one ever died from deck settlement."
The same cannot be said of improperly fastened attached
When properly constructed and attached, however, a ledger does help
with lateral stability in addition to carrying part of the deck's
load. When building a freestanding deck, that lack of stability
must be taken into account. Katwijk will often tie a freestanding
deck to the house for this purpose, but Woeste cautions against
doing so in the case of masonry veneer, explaining, "Using masonry
veneer to resist any load is a building code violation."
Figure 10. Freestanding decks require lateral
bracing. Decks attached to the house with a ledger gain much of
their lateral stability from that attachment. Diagonal bracing must
make up for that lack on a freestanding deck.
A less controversial option is to diagonally brace the support
posts (Figure 10). Most deck builders brace the outer beam on
taller decks anyway, so the method is familiar. The main
differences are that you've got two beams to brace on a
freestanding deck, and that bracing must be run both parallel and
perpendicular to the beams. On a deck that attaches to the house
with a ledger, the ledger provides the lateral stability
perpendicular to the beam.
Andy Engel is the editor of Professional Deck