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seven333

Sway bracing help

seven333
12 years ago

I completed my deck last summer and noticed some sway when we have a lot of people on it. Some info on the deck:

-Deck is 20x28 feet

-2x12 ledger is attached to the rim board with lag bolts

-6x6 posts (4 of them) are 18 feet away from the house, inset 2 feet from the ends of the deck

-2x12 joists are spaced 12 inches apart

-2x12 beam is carriage bolted through the posts

-Composite decking (MoistureShield) is run perpendicular to the joists

-Double joist on one end, single joist on the other but 8 feet of it is lagged to the house (family room jut out)

-Deck is approximately 6-7 feet above grade

-Deck passed inspection

-Can probably attach a diagram if needed

We considered a 2nd set of posts about 10 feet out but wanted to keep the area under the deck clear for a future patio. I've installed 2 sets of blocking between the joists but that seems to have had minimal impact on the side sway. I'm having a large gathering in about a month and would like to tighten things up. Any ideas? Thanks!

Comments (8)

  • sombreuil_mongrel
    12 years ago

    You need some diagonals before people get hurt.
    1) underneath fastened to the bottoms of the joists. from corner to corner, or in a vee out from the house corners. 2x4 is adequate.
    2) Diagonal x-bracing from post to post. Parallel to the house. They must start high and go low. I would use 2x6 and 1/2"x6 lags. These can be hidden by lattice or other screening materials if the look is off-putting.
    The sway can be from racking, not from lack of support.
    Casey

  • seven333
    Original Author
    12 years ago

    Thank you, Casey! How are the 2x4s attached to the ledger, beam and joists? Just screws to the underside? Is there some sort of cable or metal bracing that I can use in place of the long 2x4s? Will these be sufficient or will the x-bracing be needed? My hesitation on using the x-bracing is blocking access to the underside of the deck.

  • seven333
    Original Author
    12 years ago

    Bump.
    Any other advice? I have 1 month until the party and would like to get this sway issue fixed. Thanks!

  • seven333
    Original Author
    12 years ago

    Bump.
    Any other advice? I have 1 month until the party and would like to get this sway issue fixed. Thanks!

  • zver11
    12 years ago

    See Decks.com deck construction guide-has some pictures. As a general guide, use screws for loads that pull/push in direction of screw. Use nails for shear loads(push/pull perpendicular to direction of nail). Large lag bolts can do either. Thus, screws not appropriate for this bracing. Either nails or lag bolts.

  • brooklyndecks
    12 years ago

    That's a big span for the joists. You should have installed another beam at the midpoint, with posts.
    I agree with Casey about the 2x4 V brace from the 2 corners by the house going out to the middle of the rim joist...screwed to each joist.

    steve

  • seven333
    Original Author
    12 years ago

    Thanks. The reason for the large span was to keep the underside of the deck open for a patio. If all else fails to control the sway, I'll put one in somehow.

    Is there any metal bracing that can be used under the joists for your suggestion instead of a 2x4 or 6? A cable of some kind? Thanks again!

  • sombreuil_mongrel
    12 years ago

    Cable is not as effective; you would need to run 2 cables in an x pattern- both directions- so one is always in tension, but they only attach to the extreme points; a 2x4 attaches wherever is crosses a joist, and is equally good in compression or tension. And much less costly.
    Casey