# Deck swaying too much...help needed



## Daniel Holzman (Mar 10, 2009)

Since your deck passed inspection, I assume it was built to local code. You did not mention installation of diagonal bracing (sometimes called sway bracing). For a large deck like yours, with only four support posts, diagonal bracing is essential to minimizing deck movement. Check out the _Prescriptive Rediential Wood Deck Construction Guide_, written by the American Forest & Paper Association, which is based on the International Residential Code (IRC). When I pulled my deck permit, the building inspector gave me a copy of this guide, and said "follow it", which I did. Good diagrams, good discussion about every aspect of deck building.

On pages 14 and 15 of my guide (which is the 2006 IRC version) there is a full discussion about diagonal bracing, how to install, where to install. If you don't have diagonal bracing, that could be the source of your issues.


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## Ron6519 (Mar 28, 2007)

Post photos of the deck, diagrams aren't too much use.
Agree with Daniel about the bracing. That size deck, that far off the ground, with that weight potential would need significant lateral bracing.


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## SteelToes (Oct 5, 2010)

Also your composite decking...

Is it screw down type or grooved hidden fastener type ?


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## Seven333 (Aug 9, 2011)

Decking is screwed down. I'll try to get some pics once the ground dries a bit. Thanks!


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## Seven333 (Aug 9, 2011)

Bump for pictures...does this help at all? Thanks!


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## Ron6519 (Mar 28, 2007)

I'd put diagonal bracing from each 6x6 to the carrying beam above.


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## Seven333 (Aug 9, 2011)

Thanks, Ron. Are the diagonal braces more effective than the metal "T" braces that span the beam and post? Would horizontal bracing under the joists be even more effective?


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## Ron6519 (Mar 28, 2007)

Seven333 said:


> Thanks, Ron. Are the diagonal braces more effective than the metal "T" braces that span the beam and post? Would horizontal bracing under the joists be even more effective?


You're getting movement from the base of the post because it's basically sitting on the concrete. I would think the diagonal bracing from the posts to the beam would be most effective.
You can try whatever you want and see if it helps. I can't see the horizontal bracing doing anything, as it's the posts that are swaying.


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## AGWhitehouse (Jul 1, 2011)

I second Ron that the most effective measure would be the diagonal bracing at each column.


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## Daniel Holzman (Mar 10, 2009)

The previous two posts are correct, horizontal bracing will do very little because you lack the triangle effect. Diagonal bracing from post to beam is effective because it creates a triangle, and any movement of any element of a triangle forces another element to go into tension or compression. Since wood is very strong in tension and compression parallel to the grain, and stiff in that directions, the effect is to minimize movement.

With horizontal bracing, the entire deck can move, assuming each joint rotates. Since the joints are typically nailed in, rotation is easy, and you can get whole deck movement. For details on how to install the diagonal bracing, see the Prescriptive Guide I mentioned, it has diagrams and a description. I am uploading a photo of my deck showing the diagonal bracing for your information as well.


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## Joe Carola (Apr 14, 2006)

Seven333 said:


> Thanks, Ron. Are the diagonal braces more effective than the metal "T" braces that span the beam and post? Would horizontal bracing under the joists be even more effective?


Do it like this.


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## Seven333 (Aug 9, 2011)

Wow, thanks everyone! So is a 2x4 as shown the preferred material? I've seen people use 4x4s but attached them to the inside of the posts, not front and back like the guide and in the attached pic. Seems like front and back would provide more surface area. How long of a piece should I use? And this may sound silly, but won't the bolts (carriage or lag) weaken the posts somewhat? Thanks again! This puts my mind at ease. I'm really amazed that the inspector didn't say anything...


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## Ron6519 (Mar 28, 2007)

Seven333 said:


> Wow, thanks everyone! So is a 2x4 as shown the preferred material? I've seen people use 4x4s but attached them to the inside of the posts, not front and back like the guide and in the attached pic. Seems like front and back would provide more surface area. How long of a piece should I use? And this may sound silly, but won't the bolts (carriage or lag) weaken the posts somewhat? Thanks again! This puts my mind at ease. I'm really amazed that the inspector didn't say anything...


I'd use 2x4's for the bracing. The bolts for the bracing won't weaken the 6x6 any more then the top beam bolts.
The longer the bracing, the more stable the deck.


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## Joe Carola (Apr 14, 2006)

Seven333 said:


> Wow, thanks everyone! So is a 2x4 as shown the preferred material? I've seen people use 4x4s but attached them to the inside of the posts, not front and back like the guide and in the attached pic. Seems like front and back would provide more surface area. How long of a piece should I use? And this may sound silly, but won't the bolts (carriage or lag) weaken the posts somewhat? Thanks again! This puts my mind at ease. I'm really amazed that the inspector didn't say anything...


I just drew that real quick. Nail the 2x4's on the back side of the 6x6's so that you don't see them as much.You don't have to bolt them.


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## dvatt (Mar 18, 2009)

You supposed to use at minimum a 6" wide board according to Ibc. Go under your deck with a 5/4 x 6 pt deck board and place it diagonally across the underside of all the joists. This will stiffen it up surely.


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## Seven333 (Aug 9, 2011)

Joe Carola said:


> I just drew that real quick. Nail the 2x4's on the back side of the 6x6's so that you don't see them as much.You don't have to bolt them.


Attach to both posts or to the bottom of the post and the beam?

@dvatt - are you suggesting the horizontal deck board in addition to the diagonals on the post/beam or instead of?

Thanks.


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## Joe Carola (Apr 14, 2006)

Seven333 said:


> Attach to both posts or to the bottom of the post and the beam?
> 
> @dvatt - are you suggesting the horizontal deck board in addition to the diagonals on the post/beam or instead of?
> 
> Thanks.


Both posts is all you need to do.


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## dvatt (Mar 18, 2009)

Go with the diagonal underneath the deck first that will help. It will tie all of the joist together. Running deck boards on a 45 degree is always wise as it really stiffens up a deck. You could 
Make an x and go from corner to corner to help tie everything in. Now if you have bounce in your deck it would require another drop beam.


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## Daniel Holzman (Mar 10, 2009)

I am not familiar with IBC rules, my town uses IRC. See page 14 of the Prescriptive Guide, figure 22 shows 2x4 typical for the diagonal brace. Also, in the diagram, the brace runs from the post to the beam, and diagonal braces are shown on either side of the post. You can certainly run from post to post as Joe Carola showed, it requires a longer 2x4, but may increase stiffness slightly versus post to beam.

I can say that my deck has no detectable sway, and I used 2x4 bracing from post to beam.


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## Seven333 (Aug 9, 2011)

Decisions, decisions...

If I go with the under joist bracing, is there some kind of metal or cable that I can use versus a deck board or 2x4 or 6?


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## AGWhitehouse (Jul 1, 2011)

Seven333 said:


> Decisions, decisions...
> 
> If I go with the under joist bracing, is there some kind of metal or cable that I can use versus a deck board or 2x4 or 6?


I don't think you NEED the under joist brace. The post to beam brace will work wonders...

I've installed the post to beam braces and no joist braces on three decks now and they were all solid. So, I would start with the post to beam and if you want more then do the joist. Your best bang for your buck & time will be the post to beam braces.


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## dvatt (Mar 18, 2009)

If you do that long bracing from post to post it looks terrible. Just brace from post to drop beam


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## Seven333 (Aug 9, 2011)

Guys, thanks again! This is at the top of the to-do list and I'll report back once completed! If I had to do the deck over again, I'd add more or bigger posts and use diagonal decking! Live and learn...


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## Ron6519 (Mar 28, 2007)

Seven333 said:


> Guys, thanks again! This is at the top of the to-do list and I'll report back once completed! If I had to do the deck over again, I'd add more or bigger posts and use diagonal decking! Live and learn...


You would still need the bracing to properly stabilize the deck.


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## Joe Carola (Apr 14, 2006)

dvatt said:


> If you do that long bracing from post to post it looks terrible. Just brace from post to drop beam


How is that any different than what I drew? I drew the brace running from the bottom of the post to the end post just under the girder.


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## dvatt (Mar 18, 2009)

They should be about 2 feet long and the interior bracing on the post would form y's the pic you drew looks amateur


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## mkb63 (Aug 13, 2011)

*Cross bracing a FREE STANDING elevated deck*

Thanks for all of the posts about the deck cross bracing. This deck luckily has the ledger board attached to the house for lateral stability at one end. 
I have a similar but what seems like a more complicated problem.
I built a completely freestanding elevated platform (9ft up)for my kids playset (12x18) to be built off of. It rests on (6) 6x6 posts sitting on 10" diameter concrete piers, with doubled up 2x10s acting as beams between each pair of posts.
After assembling the posts, beams and joists the platform had a serious sway on top, despite being very stable vertically. I added several diaganol braces from the joists to the beams and posts. This helped with some of the swaying, especially parallel to the beams. The swaying perpendicular to the beams was much worse. 
I am considering diagnol bracing from the beam to the base of the posts OR heavy gauge cable bolted to each side with a tensioning turnbuckle on each cable. 
Any thoughts on the two bracing methods??? or how to attach them most securely to the beam and posts?
Please note that I intend to hand a climbing wall, swings, a slide and other playset items off of this platform. 
Thanks for your insight!


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## Daniel Holzman (Mar 10, 2009)

MKB63, you may need to post some pictures. For a free standing deck, you need to brace both directions. See pages 14 and 15 of the Prescriptive Guide I have mentioned several times for a full discussion about bracing a free standing deck. I was not clear from your post exactly how you did your bracing, did you go both directions? 

There is also a discussion on page 15 of the Prescriptive Guide regarding attaching a free standing deck to the house via the rim joist. I know this sounds odd, attaching a free standing deck to the house, but it is done to minimize sway, exactly what you have encountered.


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## Joe Carola (Apr 14, 2006)

dvatt said:


> They should be about 2 feet long and the interior bracing on the post would form y's the pic you drew looks amateur


Never said it looks good because it doesn't. Looks aren't going to solve his deck swaying problem. I don't think your way will solve the problem. Running the braces the way I drew will definitely solve his problem.


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## dvatt (Mar 18, 2009)

You must be the personality type not the looks type best of luck


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## Joe Carola (Apr 14, 2006)

dvatt said:


> You must be the personality type not the looks type best of luck


Brilliant response! When you build your first deck...let us know how it goes.


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## fulton 22175 (Mar 16, 2011)

joes way will work the best after all its underneath the deck unless theres going to be people who are going to party underneath then what does it matter what the heck it looks like , i like how you guys seek advice and then when you get it it doesnt seem good enough


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## Ron6519 (Mar 28, 2007)

mkb63 said:


> Thanks for all of the posts about the deck cross bracing. This deck luckily has the ledger board attached to the house for lateral stability at one end.
> I have a similar but what seems like a more complicated problem.
> I built a completely freestanding elevated platform (9ft up)for my kids playset (12x18) to be built off of. It rests on (6) 6x6 posts sitting on 10" diameter concrete piers, with doubled up 2x10s acting as beams between each pair of posts.
> After assembling the posts, beams and joists the platform had a serious sway on top, despite being very stable vertically. I added several diaganol braces from the joists to the beams and posts. This helped with some of the swaying, especially parallel to the beams. The swaying perpendicular to the beams was much worse.
> ...


The bracing needs to be rigid on both sides of the post. I know you want to minimize the visual under the deck, but I don't think you can avoid the 2x4 bracing.


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## Ron6519 (Mar 28, 2007)

dvatt said:


> You must be the personality type not the looks type best of luck


Can we put some punctuation in there somewhere, anywhere?
There are commas and periods out of work.


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## Seven333 (Aug 9, 2011)

Bump.
I plan on installing the sway bracing this weekend and wanted to follow up with a couple questions. 

Do you think I could make upside down Vs between the posts (top to bottom) instead of using 1 diagonal between the posts? The upside down Vs would still allow easier access to t.e underside of the deck. Or is the roughly 45 degree angle with the one diagonal make a bigger difference?

ALso, tonight I clamped a couple 2x4s between 2 of the posts and shook the deck...couldn't discern any noticeable difference in the amount of sway. I'm sure part of this is because the bracing was only clamped and not nailed. Is it worth it to try to nail these shorter pieces at every post or will I ultimately be disappointed? I'm more concerned with safety than appearance and functionality but would like the best of both worlds if possible. Who wouldnt? 

Thanks again for all the advice!


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## Missouri Bound (Apr 9, 2011)

If you want to brace the deck but not see the bracing, you could attach 5/4 to the bottom of the deck diagonally. Serves the same purpose as installing the deck at a diagonal and is nearly invisible.


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## dvatt (Mar 18, 2009)

But wait I suggested that and got told I don't know anything!!!!


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## Missouri Bound (Apr 9, 2011)

dvatt said:


> But wait I suggested that and got told I don't know anything!!!!


 Yes you did. I didn't steal it, I just missed it. Maybe your sarcasm had something to do with the criticism.


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## redwood (Apr 10, 2011)

Where I live (earthquake country), none of these suggestions would pass inspection by themselves. Way more bracing required.

A poor pic representing the bracing, but you get the idea.


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