Solid Post Bases

Greg Di

Is it just me or is it impossible to get a flimsy Simpson or USP adjustable post base to actually hold a 4x4 post without wiggling and swaying?

For instance, take a 6' 4x4 and put a double 2x10 girder on top. You can push and pull the girder around a lot because the post bases don't run up the posts far enough to actually brace them. Sure, they are great for uplift, but what about sway?

It seems to me that no matter how hard you crank down the nut on the 1/2" bolt, the gauge of the post base metal is so flimsy that the posts wiggle as the bases flex and twist. Yes, the post is secured via nails into the flange, but the sway is just ridiculous. We end up having to install a ton of bracing to take out the movement created by these code required bases. HFS systems don't help the situation either as face screwing a board would provide more rigidity.

Anyone have a better way?

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concretemasonry

You just must have a deck that has adequate bracing the two directions.

You may torque on the bolts and screws and think it is good enough when you walk away after getting paid. The wood will shrink or dry out and you will have an unsafe deck and possible liability if you had any input on the design, layout or bracing.

You have just used the wrong method of connection to the foundation for the deck design.

An alternate is putting the posts into the deep concrete piers, try to plumb them and cut off to the right height. When the ground dries, gets wet of heaves you have the same problems.

It is not a new problem and it is seen very often on a quick deck job with no good real design except for looking at the vertical loads from tables.

You could try to come up with a moment-resisting connection to use as others have, but few people (including Simpson) have not been willing to assume the liabilities for failure and possible fatalities.

Dick

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Dick

Engineer, designer and consultant recently active domestically and internationally on construction and design in about 35 countries.

Greg Di

Is that post a question or an answer.

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redwood

I think that if you look in the simpson catalog, it will state that the bases are not for non top supported structures.

If your post heights exceed 3', you need to add bracing. If you are attached to the house, you may not need bracing perpendicular to the house.

You don't usually need to add bracing in every bay, though.

I usually use CBSQ's, they seem to be a little stiffer then even the CB's with bolts.

You could use a long MST strap and set it in concrete along side the post base and it should give pretty good lateral support in it's width direction.

Mark

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Mark
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WarnerConstInc.

Is that post a question or an answer.

Yes.?

WarnerConstInc.

Stapping like the tie downs for a mobile home over a crawl and such? That seems all right, you would have to use stainless steel.

concretemasonry

Greg -

It was an answer telling to learn more about what you are trying to do without without undestanding what goes on with decks and not have failures/problems. It was meant to try to help you.

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Dick

Engineer, designer and consultant recently active domestically and internationally on construction and design in about 35 countries.

Greg Di

Dick, I understand the engineering of decks. I don't need help with that.

Code requires the use of post base standoffs and they are not as solid as posts buried in concrete. My original post was to see how other deck builders are addressing this issue because I'm sure it's not limited to me.

The code requires post standoffs and prohibits direct post burial. It is a double edged sword of sorts.

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mickeyco

Out here you can pin the the base (I don't think the IRC prohibits it anywhere) and use an angle for uplift. Maybe a mix a few pinned and a few with post bases. You could also use the bolt through brackets (no notching) to attach the girder to the post (I prefer to notch, some areas here require no notching and through bolts).





Use these and pin and bolt



Ran across this looking for the picture above.




.

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deckman22

Greg, it is a problem that we all deal with. I've never seen a simpson post base that does a good job with sway. On decks that are up high & need sway bracing I use those flat VHA wind brace straps, they're about 1 1/2" wide flat galv. metal with lots of holes. They have good tinsel strength one way only so you have to criss cross them. You can install them on the top or the bottom of the joist, but on the top you have to notch the joist to make it flush. On pergolas & pavillions where I don't want a bunch of bracing I have a welder make custom post base. 12"x12"x1/4" steel plate w/flanges spaced according to size of post, the flanges are also 1/4" steel that run perpendicular to the plate 16-18" long with 3 holes for 1/2" thru bolts, width again according to post size. 4 pieces of 1/2" re-bar or j-bolts are welded to the bottom of the plate to hold them to the concrete. They do an excellent job for sway so braces are not needed. The down side is they cost 50 bucks apiece & must be placed in wet concrete with precision.

We do our footings different than you all up north that have to deal with frost lines & such. I use 24" square forms out of 2x6's so those custom bases are pretty easy to install into the wet crete if your boxes are all lined up & level. Working with sonotubes it might be tougher. The size of the plate may need to be downsized & the re-bar on the bottom longer.

There's a pic of them on my site the first time I used them on a park pavillion about 12 years ago.

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Chris G

No connector that I know of is going to provide lateral stability. Even if it's 2 feet long and buried a foot deep into the concrete, there is just too much leverage in a 6 foot post to stop it from swaying.

Are these free standing decks? It shouldn't be too much work to brace a deck attached to house. How are you bracing them now?

I suppose you could bury steel posts in concrete, does the code allow for that? Expensive though, and you have to put a sleeve on them to make them look good.

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jeffaah

I agree about the post bases....but they are doing thier job. Thier job is to anchor the bottom of the post to prevent it from kicking out and prevent uplift. I would never count on a base to prevent lateral movement. Thats not what they are designed for. Simpson will be happy to sell you a slew of metal connectors to prevent lateral movement.

Personally, I always add enough diagonal cross bracing. Usually just installed with Timberlocks/ledgerlocks or some other fastener. It makes the deck VERY sound laterally, I have no worries and it doesn't take long at all.

Greg Di

That's what we do too, but you'd think there'd be a cleaner way in 2008!

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RobertCDF

I usually use EPB66 post bases... I like these a little better than most. Are the perfect? No but they are better than the ones you attach with a redhead.

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mickeyco

A EPB66 won't work on a 4 x 4.

.

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RobertCDF

Then use an EPB44

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mickeyco

I know I was goofing around.

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RobertCDF

I figured you were being an ass... But your right I did need to clarify. I did not read the thread real well to see 4x4.

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Robert Shaw
Colorado Springs Custom Decks
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