Wobbly post using simpson post base

On my new deck build, 3 of the 14 posts are a bit wobbly. They are all 6x6 PT posts ranging in height from approximatly 3' to 4' and rest on a 12" diameter concrete footing and are tied to the footing using simpson post bases anchored to a J-bolt. They are held in place using a washer, lock washer and a nut.

11 of the 14 posts are extremely stable, yet 3 are wobbly. It appears that there is about a 1/16" front-to-back rocking movement under the post base, which translates into a much larger rocking motion at the post tops (approximatly a 1/4" front-to-back movement at the top). Side-to-side is very stable. I've tried tightening the base's nuts and resetting the posts and I still get the wobble.

The footing, j-bolt, base and post are all level, but I still get the wobble. It's not much and I'm not sure if it's a cause for concern, but I would sure hate to build the entire deck and it become a major problem.

Do you have any suggestions on what to do? I was planning on replacing these 3 post bases with new ones thinking there may be a defect, but wanted to pose the question before I went through the trouble.

Thanks in advance.

 

Wow that's a lot of holes/posts!!!! Why so many? Big deck?

Anyway - the rocking can only be from the base not sitting on the cement perfectly, or the wood not setting on the base perfectly. In any case, in my opinion, that's not much rocking and it will go away easily once you secure everything to the framing.

In my opinion - just keep going!

 

I figured things would stabilize, but the other posts are so stable, the wobbly ones concerned me.

Unless someone else says different, I will not worry about it.

[QUOTE=deckgrasshopper]Wow that's a lot of holes/posts!!!! Why so many? Big deck?
QUOTE]

The deck for the most part is 16' by 22', but wraps around a partially cantilevered kitchen with a 4'x4' extension for the stairs. It's a modified L-shape. In addition, it's free-standing and has 2 45 deg corners.

With it being free-standing and not exactly being a rectangle, there were a lot of posts. After digging the footings, pouring the concrete and attaching the posts, I realized that I could have elmininated 3 of the 14 posts by cantilevering the deck near the house, but the old deck was still in place and on paper, it didn't look right.

 

Tying the posts to the rim joists will stabilize them considerably and take out 99.999% of your "wobble" The main purpose of the simpsons is to keep the post from moving laterally, and the wobble is "normal". Just make sure you plumb them when you attach them to the deck rims.

 

Once the cross-bracing between the posts and the beams and from post to post, the wobble will go away. I never use the style of Simpson post base that you are talking about. I use PBS or CBSQ's. Either is embedded in the column of the footing, not bolted to it. And I wait 3 days after pouring the footings before I start framing the deck. Never have had a wobble problem.

 

I agree with lefty.

Anything bolted or nailed is considered a "pinned" connection that cannot resist rotation at the point of connection. Because it cannot resist the rotation, it will wobble (either now or eventually). This kind of connection needs diagonal cross-bracing to be structurally sound and comfortable to deck occupants.

Even with embedment of the connector in the concrete, some cross bracing is desired for stability. For a large, high or a deck in a seismic area cross bracing is definitely needed. It is not necessary to brace every bay, but some must be braced in both directions.

One of the good things (maybe the only one) about a deck supported by a ledger attached to the house is the lateral support given by the house. Even these can use some type of lateral bracing in some cases.

Dick

 

Just to give everyone an update, I purchased 3 new simpson bases and installed them and the wobble went away completely. The bottoms of the 3 anchors were slightly warped, which was giving me the problem.

Our local inspector specified Simpson bases as the "preferred" connection between the footing and pier, so that is why I used them. In the future, I will go with a different method as these were really a pain to install correctly.

Thanks for the help.

 

I have to add that if you think it was a pain to install these correctly, think about how much trouble it would cause you if you installed one of the 'sunk in the concrete' post bases incorretly.... (not plumb or not perfectly aligned).

The beauty of the bolt system is the near 2 inches of front/back play you get to use before you tighten the bolt. Allows you to get your 'near-perfect' alignment of those bases to 'perfect'. If you find out at the end that one of those bases is warped, you just pick it up and remove it. What happens if you place those permanent posts a bit off...or a bit off plumb?

I'm still a fan of the bolt bases for the beginning DIY'er and the wobble in 3 of 14 is just not an issue. They are also the preferred connection by my inspector and the underbracing was not required (and I asked about it). Then again, my deck was attached to a house borne ledger.

Sounds like you are doing a top-notch job in replacing those and you deck will certainly come out great. Thanks to all for the neat discussion.

 

Another thing to do with the bolt bases, is to use the simpson epoxy to fill the hole first, then install the lag shield and bolt/nut. Seems to stiffen it up pretty good, and still allow flexibility.