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Re: cantilever wood deck

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Nels,

Thanks for the input. I too expected the the decking to resist the movement even though I wouldn't want to calculate for it. The cantilevered decks are about 40 foot long and projects 10 feet from the house. The movement does appear to be with the nailing on each 2x4 to the joists. The original construction drawings indicated lapping with the floor joists 10 feet and specific nailing is called out connecting the two. Verification is not possible without removing ceiling drywall. The lower deck has a steel spiral staircase that connects 7 foot from the house and extends to the ground 8 feet below. This lower deck deflects laterally just in the outermost 3 feet as the stair provides bracing. But even in that last 3 feet, it's easy to see the movement between the decking and the joists.


Steve P

Nels Roselund, SE wrote:

Steve,

What is deforming to cause the deck to flex?  Two nails per deck-piece to
each the joists should provide a "diaphragm" that is pretty rigid in shear.
Does the deck need to be re-nailed?  Or screwed down?

Is the flexing due to lack of anchorage of the structure to the house?
Perhaps the end joists need to be anchored to the floor framing of the
house; hardware that connects to the deck framing and, through the wall, to
the floor framing at each end may be needed to provide chords for the
cantilever deck diaphragm.

How about the shear connection of the deck to the house?

Nels Roselund
Structural Engineer
South San Gabriel, CA
njineer(--nospam--at)att.net


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