How tall of a 4x4 post can I use if it's going to be free standing without much additional support?

by Jacque
(Colorado)

After building our deck we realized that we don't have much privacy from our neighbors so here is what I'd like to do...

Use the 4x4 Titan Post Anchor to install 3 posts (4x4) about 4 feet apart and about 7' high. Then I'd like to hang outdoor curtains from them. Will I have enough support with the Titan?

Comments for How tall of a 4x4 post can I use if it's going to be free standing without much additional support?

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Jan 23, 2012
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Thanks!
by: Jacque

Thank you so much, you've been a big help. I'll be sure to post pictures when I get it all done! (which might not be until spring but you never know!) Thanks again, Jacque

Jan 23, 2012
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The 6x6 anchor is perfect for this application
by: Editor-Rich Bergman

I would highly recommend the 6x6 post for this height for performance and because the dimensions of the post are right. The 4x4 over 7 feet just looks to much like a thin spindle even though it would suffice for your application.

You will find that for the extra $15 or $20 on the 6x6 anchors you will very happy with the balance of the look and when you bump into it you will know right away you hit something sturdy.

That is my recommendation.

Jan 23, 2012
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Load resistance..
by: Jacque

The only thing that these posts are going to be holding is going to be a steel rod (running through the top of all three) with curtains hanging from the rod.

There is actually a fence on the other side of it so I'm only using it to create a privacy screen. our deck sits a bit higher than my grouchy neighbor wants!) With that being said what would your recommended height be for each post. And would you do 4x4 or 6x6? Thank you so much!!

Jan 22, 2012
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Keep posts closer together or use 6x6 posts
by: Editor - Rich Bergman

The short answer is Yes and Maybe Not - depending on the load resistance you are looking for. Let me explain.

We have done so much engineering now on our 4x4 and 6x6 anchors that I can recite almost any typical load value or range for various anchor with various wood species, moisture content and post spacing or single posts.

Just for your information our 4x4 and 6x6 post anchors passed the AC 273 test procedure set out by the IRC for residential guard rail applications in September 2011. 36" 4x4 post can be spaced up to 6' on center, and 6x6 posts up to 8' on center.

At 7 feet hight you find a single post will have a lot more leverage and therefore generate a much greater moment of force at the base. It will wobble at least twice as much as at have that height. But if built as a triple post arrangement at 4 feet apart the wobble is reduced significantly because it is shared among the entire system of posts and connecting rails.

Lets start with some real test data at 36", then 42" to give you a sense of what you might experience at 7'. By the way we have never tested single posts or rails at 7'. This should help you decide what is right for you.

The end post of a 36" two post and 6' rail section has surpassed by over 2.5X the guard rail code minimum pointload of 200 lbs. So that is over 500 lbs and that is using softer (SPF stands for spruce pin fir) pressure treated pine lumber.

We have tested 42" two post and 6' rail sections consistently well over 400 lbs on the end post. We have also tested the same 42" post and rail assembly and added one of our custom horizontal Chicago bolts through the bottom of the post and anchor and taken the end post in this 42" assembly to 500 lbs. I suppose if we shorted the post spacing to 4' the load value would increase somewhat.

So based on this we can predict that that bringing posts closer together will stiffen and increase the strength of any given assembly. The only thing we can't say is what the final load to failure would be at 7'. Certainly it would be much less.

This is only an issue if your surface is 30" or higher above the ground because then it would have to function as a guard rail and the guard rail standards apply.

If you are not above 30" then it is only up to you personally how strong you would like to be.

You might also wish to see this video of a 6' 6x6 post fence application on a concrete wall which turned out to be very sturdy. See the installation here:

Watch here...



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