Deck Uplift
Deck Uplift
(OP)
I have a residential client who wants to build an inexpensive deck by laying 4x6 PT sleepers down on a bed of gravel and simply attaching cedar decking to them. My only concern is the possibility of wind picking this thing up in a hurricane. It probably will only weigh 7 PSF. This is a 90 MPH, Exp B zone. Is this a reasonable concern? I guess, technically, there is no wind speed at ground level and very little at 4" above that.
Thoughts?
Thoughts?
RE: Deck Uplift
Also concerned that the treated lumber would deteriorate eventually, which it will I would think.
RE: Deck Uplift
Any idea on shape factors for this thing?
RE: Deck Uplift
Would be fairly cheap..
It just needs a little resistance so it can't pick up and then grab more wind load..
RE: Deck Uplift
They don't want to use any concrete. We haver talked about mobile home tie-downs. Just trying to get an idea of the uplift I am dealing with. It is 12'x40'
Even fence post footing don't have significant mass so I don't know how effective they will be.
RE: Deck Uplift
RE: Deck Uplift
I input a 6" high 30 ft. x 30 ft. "building" into our wind spreadsheet calculator using V = 90 mph, Exp. B wind.
This is C&C wind with At = 100 s.f.
The attached is the results - about 13 to 15 psf uplift. Not sure if I buy that but it at least gets you a semi-rational number.
RE: Deck Uplift
I would put a 4x4 PT in each corner, penetrating about 3 feet in the ground and backfill with wet soil. It takes a lot of force to extract those posts, so would easily hold down a deck.
RE: Deck Uplift
FWIW, in exposure B, ASCE7 has Kz the same up to 30 ft., so my 6" tall structure does not make a difference as far as uplift (and ASCE) is concerned.
Thanks to all that replied
RE: Deck Uplift
RE: Deck Uplift
When I said my 6" tall structure does not make a difference, I meant it has the same uplift as a 30ft. tall building - not that it had no uplift.
RE: Deck Uplift
Mike McCann
MMC Engineering