The building codes typically require
that decks be able to support the same live load
as the rooms to which they connect. In a residence,
that's 40 psf. for a 300 sq. ft. deck,
that's a total of 12,000 lbs.
Take, for example, a 2 by Southern
Pine deck ledger board attached to the house
framing. With a 1/2" diameter bolt and a single
shear applied perpendicular to the grain
for "normal"duration, the allowable shear load in
the bolt is 330 lbs. Of course, the bolt
itself could handle many times that load, but what
will fail first is the wood; that's what
limits the capacity to 330 lbs.
For a deck with joists spanning 14
ft. with 2x10's 16" on-center and 2x6 decking, the
weight of the deck itself is approximately 7.3 psf.
Add this to a design live load of 40 psf,
and the total load is 47.3 psf. One half of this
load must be supported by the ledger
board at the house. Simple multiplication (14 ft.
x 47.3 psf x 1/2) gives a load along the
ledger of 331 lbs. per foot.
The "Stratton Bracket®"
greatly increases the "shear" of the wood because the wood
"sits" in the brackets. |
Decks