Eliminating Freestanding Deck Sway

48379 Views 83 Replies 17 Participants Last post by Rio, Jul 28, 2014

JR Shepstone

Discussion Starter · Jul 25, 2014

Ok so this might be my first time posting pictures of my work, but I've got to do it to figure something out.

I'm building a 14'x14' freestanding deck. 2' cantilever front and back. 2x12 beams running parallel to the back of the house. 2x10 floor joists running out to the yard.

My issue is this: I have zero left to right movement in the structure. However, I have a slight shimmy front to back. I have knee braces installed. I'm not sure if they're not set low enough... Or, would a hurricane strap eliminate the sway that I have going on?

I didn't realize the pictures were so dark, I can get some in the daylight tomorrow evening.

Table Bridge Wood Hardwood Furniture

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tenon0774

· #2 · Jul 25, 2014

JR Shepstone said:
Ok so this might be my first time posting pictures of my work, but I've got to do it to figure something out.

I'm building a 14'x14' freestanding deck. 2' cantilever front and back. 2x12 beams running parallel to the back of the house. 2x10 floor joists running out to the yard.

My issue is this: I have zero left to right movement in the structure. However, I have a slight shimmy front to back. I have knee braces installed. I'm not sure if they're not set low enough... Or, would a hurricane strap eliminate the sway that I have going on?

I didn't realize the pictures were so dark, I can get some in the daylight tomorrow evening.

You're deck is swaying on the posts regardless of your "knee braces".

Lock all the posts together a little lower than your knee braces with let in "beams" and bolts.

I sounds like your getting "wobble" in the "stems".

Based upon how I see you ran the decking, the posts are still wobbling "across" the decking.

You wouldn't have this issue if you could attach to the house structure, however;

In municipalities now, ( because of all the deck collapses, in the news ) you can no longer attach to the house.

( great, more deck collapses to come, even with this STUPID new rule)

Sorry. Back to you're point:

Unitize all the posts below the knee brace.

Even if you were to "let in" and carriage bolt all your post perpendicular to the decking, and call it a day, you're going to eliminate that lateral movement.

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owattabuilder

· #3 · Jul 25, 2014

The longer the knee brace, the stronger the structure and the less sway.

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Tinstaafl

· #4 · Jul 25, 2014

Yep, longer braces. Though with a quick glance at those pics, it doesn't seem as though you should be having a problem with well-rooted 6x6's.

JR Shepstone

Discussion Starter · #5 · Jul 25, 2014

tenon0774 said:
You're deck is swaying on the posts regardless of your "knee braces". Lock all the posts together a little lower than your knee braces with let in "beams" and bolts. I sounds like your getting "wobble" in the "stems". Based upon how I see you ran the decking, the posts are still wobbling "across" the decking. You wouldn't have this issue if you could attach to the house structure, however; In municipalities now, ( because of all the deck collapses, in the news ) you can no longer attach to the house. ( great, more deck collapses to come, even with this STUPID new rule) Sorry. Back to you're point: Unitize all the posts below the knee brace. Even if you were to "let in" and carriage bolt all your post perpendicular to the decking, and call it a day, you're going to eliminate that lateral movement.

I understand exactly what you're saying. The thing is the bottom of the joists are about 6'-3" off the ground. Still allowing it to be a usable space for whatever.

I would prefer if I didn't have to "fence" off that area by installing a cross member.

parkers5150

· #6 · Jul 25, 2014

what are you using for hardware coming out of the footings???

Calidecks

· #7 · Jul 25, 2014

Knee braces one third the height of the post. So if your post is 9 feet, your brace would be 3 foot across and 3 foot down. That would make the knee brace 4'-3"

Calidecks

· #8 · Jul 25, 2014

Also I might add, my engineers always make me thru-bolt the knee brace.

parkers5150

· #9 · Jul 25, 2014

in the pics... your post bases look under struc'd! That being said...( disclaimer: you may have done this can't tell) the way you have your posts sandwiched between your main support beams (2 bys) should be mirrored with a double joist set up (post running thru to underside of decking) with both applications being thru bolted:thumbsup:
sorry about sentence structure ... looong day

Tom M

· #10 · Jul 25, 2014 (Edited)

The house can be used for lateral support front to back. You might not be looking for support help but laterally yes. If it sways sid to side. Throw a 2x4x12 on a diagonal underneath the joists on the flat in between the beams.

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JR Shepstone

Discussion Starter · #11 · Jul 25, 2014

parkers5150 said:
what are you using for hardware coming out of the footings???

I believe it's the Simpson ABU66.

owattabuilder

· #12 · Jul 25, 2014

Next time bury your posts 4 foot. That is what we do and the decks are very stiff. Your bolted connectuin to the beam is controling the sway in the other direction. That creates a rigid frame.

Instead of bumping the post put a 2 x 6 brace on each side and bolt through the post. Add a couple of joust to align with the braces and bolt the brace to the joist. Fasten the joist solidly to the rim and beams and that should create the rigid frame in that direction. Next time run your posts 9 inches aboce jthe beam and bolt ma joist to each side which should eliminate the need for the braces.

Calidecks

· #13 · Jul 25, 2014

JR Shepstone said:
I believe it's the Simpson ABU66.

simpson even says those provide very little to no lateral strength. It must be supported at the top.

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JR Shepstone

Discussion Starter · #14 · Jul 25, 2014

parkers5150 said:
in the pics... your post bases look under struc'd! That being said...( disclaimer: you may have done this can't tell) the way you have your posts sandwiched between your main support beams (2 bys) should be mirrored with a double joist set up (post running thru to underside of decking) with both applications being thru bolted:thumbsup: sorry about sentence structure ... looong day

The 6x6s are notched and the beams are bolted on. I did not run the 6x6 up to the top of the joists. I never knew about that. But now I do.

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JR Shepstone

Discussion Starter · #15 · Jul 25, 2014

I feel like I'm getting my movement where the joist land on the beams. I guess it's somewhat of a hinge point.

Is this something that a hurricane tie would eliminate?

Tom M

· #16 · Jul 25, 2014

JR Shepstone said:
I feel like I'm getting my movement where the joist land on the beams. I guess it's somewhat of a hinge point.

Is this something that a hurricane tie would eliminate?

Now that's for uplifting. Technically your supposed to solid block over those beams. That could help your hinge. I would still nail a diagonal on the undersidethou g .

JR Shepstone

Discussion Starter · #17 · Jul 25, 2014

Tom M said:
The house can be used for lateral support front to back. You might not be looking for support help but laterally yes. If it sways sid to side. Throw a 2x4x12 on a diagonal underneath the joists on the flat in between the beams.

That was one of my first thoughts. But I felt that the brace would just move with the deck.

Like I said, parallel to my beams I'm rock solid. It's parallel with the joists that I'm having problems.

JR Shepstone

Discussion Starter · #18 · Jul 25, 2014

owattabuilder said:
Next time bury your posts 4 foot. That is what we do and the decks are very stiff.

That's heresy!! :laughing:

parkers5150

· #19 · Jul 25, 2014

ABU's are for retro applications...next time cb66:thumbsup:

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Calidecks

· #20 · Jul 25, 2014

Tom M said:
Now that's for uplifting. Technically your supposed to solid block over those beams. That could help your hinge. I would still nail a diagonal on the undersidethou g .

I not only sold block but I add an A-35 flat from block to Beam. You need to flush your block to one side of the beam to do this. Every little bit of transfer helps.

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