Residential Wood Deck Design Wind Loads?

[omoreno80]

In looking over the DCA6 for Residential Deck design, no mention is made of wind loads. I am designing a residential wood deck around a large pool area 4' of the ground, thinking of applying the open structure wind pressures on the deck structure, but I am unable to find any reference that may show that this a design requirement. Uplift on the underside of the of deck would increase footing sizes. Has anyone dealt with this in a high wind area? Thanks in advance

 

[msquared48]

At only four feet off the ground, you are not looking at much pressure. The dead load of the deck structure should be able to handle it. I would ignore it.

I did for mine 15 years ago and have seen no problems. It too is four feet off the ground with an open X mesh wood skirting.

Mike McCann
MMC Engineering

 

[MiketheEngineer]

You could run as a "flat" roof - but at 90 mph you are only going to see maybe 13-14 psf uplift. IBC allows you to use 2/3 of the dead load of the deck to resist this. SO maybe you are at 8-9 psf TOTAL.

Basically agree w M^2 - haven't seen too many decks blow away. If worried throw in a couple of more yards of concrete running about $90 a yard around here!!

 

[MiketheEngineer]

Better answer - Put a HOT tub - big ONE in the middle and don't worry about anything!!

Invite all the local MILFS over and after your wife kills you, you will still have the deck and HOT tub.

 

[msquared48]

Hey! You been peaking at my setup?

Mike McCann
MMC Engineering

 

[MiketheEngineer]

NO - the MILF next door

 

[dhengr]

Omoreno80:

Irrespective of the MILFS at the pool, you do have to pay attention to lateral loads on the deck and properly bracing it and/or tie it into the building. In the residential wood deck design guide I’m looking at, Min. Reqr’mts., item 7, second page says “This document does not address wind and seismic design issues.” God help us, I guess they still expect us to apply some engineering judgement and experience in our designs. ASCE 7 might be used as a guide for wind loads, but after reading 60 or 70 pages of that, spending hours looking for the meaning and value of some obscure multiplying factors and running you computer for an hour or two; you might just take the projected area of the deck, double or triple that since the wind will be applied to many joists, not just the rim joist, and apply 15-20 lbs./sq.ft. and call it good. The bigger question in terms of lateral stability of the deck is, where would the worst location be for three or four drunken, 300 lb. defensive linemen, swaying in unison, to impress the cheerleaders and other guests? That’s a loading parallel to the ledger, but 10-12' away from the bldg. at the handrail, applying a high tension component at one end of the ledger, corner of the deck. Or, a group of people running to one handrail to see some commotion. That pulls the whole ledger away from the bldg. And, I suppose you’ll have trouble finding those in the codes also. I have trouble calculating those forces too. But, those are the types of loads which more often than not peel a deck away from its ledger or the building, when not connected or braced properly. And remember, jst. hardware has very poor strength values when loaded along the axis of the jst.

Obviously, you have a different problem if you have privacy walls, or several different levels of deck, or some of these wildly unsymmetrical deck plans. Also, a very heavy deck in EQ country needs some special attention.

 

[MiketheEngineer]

If I have enough MILFS - I hope the lateral loads take the thing down and I die a happy man!!