Michael Morse, president of DeckLok
Bracket Systems, responds: Formerly, the
IRC required only that decks be designed to safely
transfer all anticipated live and dead floor loads to
the foundation. What the code did not do is
define how the lateral loads (away from the main
structure) were to be transferred to the foundation.
This lack of a lateral connection requirement
has had devastating results. A segment on CBS’s“The Early Show” in 2005 cited experts as saying
that deck collapses in the United States occurred
at a rate of one per week. A study done by our company, which manufactures the DeckLok lateral anchor, validated that statistic.
Most of the decks we studied had been well
built. The collapsed decks that we saw usually
had fallen as a complete unit, still structurally
sound and intact even after hitting the ground.
No deck was overloaded. That is, the total load
on the decks at the time of collapse was far less
than the load they were designed to carry (50 lb./square foot x square footage = design
load). The decks themselves were not the cause.
The failures were at the deck-to-house connection.
This includes the deck joists, the ledger
board, the house rim joist, and the house floor
joists. Of the collapses we studied that occurred
between January 2000 and December 2006, 92
percent were attributed to the failure of the
deck-to-house connection. Decks detach from
houses due to failure of the critical connectors
to keep the two structures together.
The IRC has now recognized the deck-to house
connection to be the weak link. A deck
ledger board that is through-bolted to the rim
board still relies on the nails connecting the rim
board to the joists for the connection to the
house foundation. The house rim board and its
connection to the house joists was never
designed to support additional living space or
to resist a lateral force trying to pull it out of the
building. It was designed to resist racking of the
house and its floor joists.
Lag bolts join the rim board and the ledger
board to create a laminated beam that carries
the vertical load imposed on a deck to the house
foundation. The lateral anchors are designed to
resist horizontal or lateral loads. They keep the
rim joist–ledger board beam from pulling away
from the house. Each type of connector performs
a separate job, and both are necessary.
Use a lateral anchor for a lateral attachment.
You wouldn’t use a drywall screw to hold a ceiling
fan box or electrical conduit as plumbing.
Although each of those examples has the same
basic shape as the proper material, each also is
engineered with critical properties to perform
the intended function. Lateral anchors are specifically
engineered to maximize the performance
of the deck-to-house connection. They are
designed to work with the floor joists, to flex and
distort to preserve the holding power of the
assembly, and to resist ripping through the 2-by
floor joist.
Unlike conventional hold-down brackets,
which are often substituted for them, lateral anchors are flexible and sized to work
with 2-by joists. Hold-down brackets
are designed to resist uplift, to help
keep a house from lifting off its foundation.
To my knowledge, the Deck-Lok bracket is the only product on
the market specifically engineered as
a lateral attachment bracket.
The lateral load connection shown in
the IRC is a simplistic example in
which the house floor joists and deck
joists align both laterally and horizontally.
Deck builders will not usually be
so lucky, but the connection can still
be made. One option is to anchor the
ledger board to the house floor joists
and, with a separate bolt and anchor,
tie the deck joist to the rim board.
The concept is the same no matter
which way the joists run. The deck
must be tied into the structure of the
house. In cases when the deck ledger
runs parallel to the house’s floor
joists, install blocking between the
outer two floor joists and bolt lateral
anchors to each of those joists. This
will create a structural connection
between the deck ledger board and
the house floor system.
Many installation configurations
have already been designed and are
available for viewing and download at
DeckLok Bracket Systems’ Web site
(www.deck-lok.com).
©Professional Deck Builder Magazine
