Setting 6x6 fence posts

[Belegost]

So the fence in our backyard is a bit over 30 years old now, and a flood that had a couple feet of water running through the yard a few years ago has weakened several posts.

The fence design is 6x6 posts at 8 foot spacing, with 2x8 stringers between to mount the slats, and a 2x4 top rail. Similar to this picture:

The current posts look like 2x6x10', with about 3' set in a cement base than ends 4-6 inches below grade. I'm not real excited about having the posts set directly in the cement due to rot. So I was considering using 6x6 base brackets to surface mount the posts. However, in the past I've used such brackets for structures that have support along both axes, whereas the fence only has support along the line of the fence - I wonder if the brackets will be strong enough to handle forces pressing perpendicular to the fence (a real issue, the other day we had 60-70mph gusts coming from that direction, which started several existing posts leaning)

Anyone have experience with bracket mounting fence posts? Given that these are 6x6 treated timbers (and the existing posts lasted 30+ years) am I worrying too much about just setting them in 3' of cement?

 

[DrPizza]

I think your last sentence sums it up well - you reasoned out why - these ones lasted 30 years, and according to you, it appears that they'd still be lasting if not for the flood.

 

[echo4747]

I think your last sentence sums it up well - you reasoned out why - these ones lasted 30 years, and according to you, it appears that they'd still be lasting if not for the flood.

this... and you can further prolong the life of the posst by coating the end grain with epoxy. It is moisture that is the biggest cause of rot. The end grain is what wicks up the most moisture.

 

[Greenman]

Dip the ends of the posts in coppergreen, and put a few inches of gravel in the bottom of the post hole before the concrete. Should last many years.

 

[Humpy]

I used to only use concrete, with gravel at the base, for the posts next a gate, mostly for the added mass. Deep holes with gravel at the bottom, and fine crushed stone packed in around the posts, hold 95% as well as concrete with a benefit of better drainage and simpler installation.

 

[MagnusTheBrewer]

Pick up a plastic concrete footing form from your local home improvement store and you're good to go.

 

[skyking]

What humpy said, I never use concrete as all I see is rotted off posts in concrete. I pack in the native rock here, but I would rather import crushed rock if necessary.
I put the current fence in in 1995, no signs of rot here.
I used another post to pound the rocks in. It does the trick.

 

[Greenman]

What humpy said, I never use concrete as all I see is rotted off posts in concrete. I pack in the native rock here, but I would rather import crushed rock if necessary.
I put the current fence in in 1995, no signs of rot here.
I used another post to pound the rocks in. It does the trick.

I've seen that done with 1/4 by dust as well. I always wondered how it worked long term.

 

[skyking]

It does not drain as well as larger stuff. I think drainage is the key to post longevity.

 

[paperfist]

That fence in the picture is 30 years old? Wow looks way better than my 10 year old PVC fence!

Is there gravel at the base of the cement for drainage?

I personally hate those brackets. You have to get them set perfectly. I don't believe they are as strong as setting them in cement. And you create more rot issues with the bolt penetration and dissimilar materials.

And someone correct me if I'm wrong, but once the post is encased in the cement there really isn't any air movement going on down there and thus not a lot of rot takes place.

 

[Belegost]

That fence in the picture is 30 years old? Wow looks way better than my 10 year old PVC fence!

Keyword: similar. I didn't have a pic of my fence available, that one was just to show the construction.

Thanks for the advice, I will just stick them in the ground, and I may try just a med. gravel fill firmly packed.

 

[Greenman]

It does not drain as well as larger stuff. I think drainage is the key to post longevity.

Probably right.
I wonder if anyone has tried a layer of filter fabric to keep silt from clogging the gravel?
I'll check the JLC, I bet someone has spent some time perfecting the process.

 

[herm0016]

http://www.jlconline.com/how-to/framing/rotproof-fences_o

good stuff here.

 

[Belegost]

http://www.jlconline.com/how-to/framing/rotproof-fences_o

good stuff here.

Definitely, thanks for the link.

 

[Ettitt]

I think you made a wall with cement. These wall can protect your yard very much.

 

[Scarpozzi]

My neighbors recently had a privacy fence installed. The installers used 4x4 posts and treated 2x4s to make the frame of the fence. Then, instead of doing a solid fence, they alternated the slats so you can't see through the fence easily, but most importantly, wind gets through it. I asked the installers about the design and they stated that it's one of the better designs because of that reason. If you want to replace the fence in the future, look into those...they can be built relatively easy and cheap with 4x4s...look good if you go for the ones with the decorative tops.

Now...for your 6x6 post in concrete question. I've dropped 20', 6x6s in 3-4' deep concrete holes and they were fine for 20+ years. They are thick enough that they do bend/sway some, but for a 6'-8' fence, they don't bear any load. Your worries about the wood in concrete are valid. However, the sun does just as much damage to treated lumber as contact with concrete and 6X6 won't break off like 4x4s will. Just make sure you don't pour the concrete too low and give water a place to pool. You want the concrete flush with the ground so it sheds. Concrete is probably cheaper than those brackets. Just fix it and tell your future self to hire someone else to replace it in 20 years.

 

[Belegost]

My neighbors recently had a privacy fence installed. The installers used 4x4 posts and treated 2x4s to make the frame of the fence. Then, instead of doing a solid fence, they alternated the slats so you can't see through the fence easily, but most importantly, wind gets through it. I asked the installers about the design and they stated that it's one of the better designs because of that reason. If you want to replace the fence in the future, look into those...they can be built relatively easy and cheap with 4x4s...look good if you go for the ones with the decorative tops.

Now...for your 6x6 post in concrete question. I've dropped 20', 6x6s in 3-4' deep concrete holes and they were fine for 20+ years. They are thick enough that they do bend/sway some, but for a 6'-8' fence, they don't bear any load. Your worries about the wood in concrete are valid. However, the sun does just as much damage to treated lumber as contact with concrete and 6X6 won't break off like 4x4s will. Just make sure you don't pour the concrete too low and give water a place to pool. You want the concrete flush with the ground so it sheds. Concrete is probably cheaper than those brackets. Just fix it and tell your future self to hire someone else to replace it in 20 years.

Thanks for the idea - unfortunately this fence backs onto a city walking path, so even just to replace portions of the fence with identical new fencing requires a permit, and to make changes to the appearance of the fence would require submitting plans to the planning committee and having it go through a public hearing. Too much effort to bother.

 

[Scarpozzi]

Thanks for the idea - unfortunately this fence backs onto a city walking path, so even just to replace portions of the fence with identical new fencing requires a permit, and to make changes to the appearance of the fence would require submitting plans to the planning committee and having it go through a public hearing. Too much effort to bother.

In my experience, most of the 'effort' in those situations is just waiting around for the hearing to take place. When that day comes that you do need to replace it, I'd just hire a local fencing company that works with the city codes office frequently. Those contractors usually handle that as part of their service. Hopefully, you'll be rich then and will be able to afford it.

 

[Fake Wood Floor]

Pressure Treated Ground contact lumber for starters which you already know.
I've built an entire fence with post spikes (2x4's) but I did that because I live in bedrock country where the ground varies from bedrock to a little topsoil to a lot of topsoil. The spikes work great but they cost a lot of money. The advantage is the drainage from the bottom of the spike is fantastic and they provide a solid "shoe" on all 4 sides of the posts. The "deck brackets" that have a single round rebar looking post on the bottom won't hold up to any wind whatsoever. The 1st kid to climb over will bend the fence.

I should also say that my fence is only 4 foot tall pickets with lots of gap for wind to blow through. I have been obsessing with fences for years though and what I've learned.

Go deep with your posts.
You should (really must) go deeper than your frost line.
The post can go in concrete but the post bottom must extend through the concrete to avoid creating a water bucket to quickly rot your post. Well compacted gravel will function just fine. The trick is to really pound that gravel a little at a time. I use a 5' long heavy steel prybar designed for lifting boulders out of the ground to pound rock... it is heavy and it is a real bitch to pound gravel with such a small handle (It's about the size of a dime at the end of the bar) but you will be amazed at how "unpacked" your "packed" gravel is when you start pounding it with a steel bar like that. The bar goes through packed gravel like butter and you get a much better packed gravel.

If I had 600' of topsoil like I did back when I lived in California I'd build a fence with 6x6 like you want to. I'd bury at least 4' for a 5' fence and dig holes 5' deep. I'd pack gravel around the posts and be a very happy camper. I've read that people have had good luck coating the posts bottoms in Tar before going in the hole. I've also talked to painters who recommended setting the posts in oil-based primer (clear) and let the end grain soak up as much as possible for a couple of days.

wherever you live, the key is below frost line and plenty of post below the ground to give it strength against the wind. In your case I'd be wanting to go even deeper than 4' with the potential for strong winds and a fence that is a solid wall. No bracket will stand up to the winds with the fence you are building unless you have some post shoes custom made out of thick steel.

 

[Fake Wood Floor]

with concrete I think you should spend extra time to finish the surface so that it is smooth and tapers away from your posts (if you use concrete). Think a smooth dome with the post sticking out the top, and the concrete dome should be at least partly above ground.

If your ground freezes significantly I'd recommend using tubes to pour in (sonotubes cost a lot of money but any generic cardboard tube would work fine). The reason for this is that the smooth walls of the tube create a surface that the freezing ground can't grab onto as it freezes and lifts in the winter. If you dig with a shovel and create a sloppy rough hole you're just asking for frost heave even if you go below the frost line. The frost heave can act on the sides of your rough concrete pour and lift those posts right up. Another reason to just pack gravel and avoid concrete.