Do I really need concrete tube forms for what I am doing in my backyard?

**JPC** · 06-08-2013, 21:47

I got a post hole auger from Home Depot and I was surprised on how well it performed in my hard clay. It is an 8 inch auger and zoom it went it right down. I am going to put a 4 x 4 post in the 3.5 foot deep hole to hang my hammock (no trees). I was thinking of using an 8 inch concrete form tube but do I really to? I will be using quick dry cement. I imagine that the 4x4 will be ~12 feet from the ground not sure. Thanks.

**Steve D** · 06-08-2013, 21:53

Nope. It would be better for the concrete to fill the hole around your post entirely rather than using a form tube and having gaps.

**flatline** · 06-08-2013, 21:54

I think you will be fine without tubes.

**HeathC** · 06-08-2013, 22:07

you should be fine without the tubes. I have off my fence posts and they are only 2 feet i'm guessing (the contractor built the fence) and i'm 220 lbs.

**trouthunter** · 06-08-2013, 22:55

Hi JPC,

Concrete form tubes are used for pouring concrete above ground, not below. When pouring concrete in a hole in the ground the hole is the only form you need. Like mentioned above, the pour will be stronger if you just pour the concrete straight into the hole.
Just a couple thoughts here if this something you want to last a while......

One thing you can do is to put some gravel in the hole under the post before pouring the concrete, or pour some concrete in the hole before placing the post in the hole. Basically you don't want the bottom of the post to have any contact with the ground because it will rot from the bottom up and snap off at some point in time. This is one of the biggest mistakes people make (even contractors) when building wood fences.

If you can afford it I think you would be better off with 6 X 6 posts though, long term they will handle the lateral load of hanging a hammock better than a skinny 4 X 4.
Don't get me wrong, you're probably not going to snap a decent 4 X 4 but a 6 X 6 will be much stiffer like a real tree. 4 X 4 posts are okay for compressive loads but not live (lateral) loads.

Hope that helps,
Mike G.

**JPC** · 06-08-2013, 23:14

Thanks to all.

Interesting tip on the 6 x 6 and yeah, they are pricey. I assume the 8 inch hole would suffice for 6 x 6 and the concrete around it?

I have a Clark Flex 180. What do you think about a 6 x 6 at the head and two 4 x 4 for the ends? Or go with two 6 x 6 at each end for safety? I am ~270 pounds.

Originally Posted by trouthunter

Hi JPC,

Concrete form tubes are used for pouring concrete above ground, not below. When pouring concrete in a hole in the ground the hole is the only form you need. Like mentioned above, the pour will be stronger if you just pour the concrete straight into the hole.
Just a couple thoughts here if this something you want to last a while......

One thing you can do is to put some gravel in the hole under the post before pouring the concrete, or pour some concrete in the hole before placing the post in the hole. Basically you don't want the bottom of the post to have any contact with the ground because it will rot from the bottom up and snap off at some point in time. This is one of the biggest mistakes people make (even contractors) when building wood fences.

If you can afford it I think you would be better off with 6 X 6 posts though, long term they will handle the lateral load of hanging a hammock better than a skinny 4 X 4.
Don't get me wrong, you're probably not going to snap a decent 4 X 4 but a 6 X 6 will be much stiffer like a real tree. 4 X 4 posts are okay for compressive loads but not live (lateral) loads.

Hope that helps,
Mike G.

**Rolloff** · 06-08-2013, 23:56

He may have been referring to Sonitube.

Unless you are pouring into a water problem you can't tame, you certainly don't need them.

Sounds like you have the optimum conditions to go right ahead as is.

How deep are you setting the posts? An Eight inch auger or post hole digger will be fine but you'll need to go deeper than that. IMO

You can also drill a couple holes 6 or 7 feet behind each post, and sink down guys that allow you to tension the posts with cables, should things shift. It's also worth considering raking the level of the post slightly to allow for it to remain level under load.

Good Luck!

**trouthunter** · 06-09-2013, 01:19

Originally Posted by JPC

Thanks to all.

Interesting tip on the 6 x 6 and yeah, they are pricey. I assume the 8 inch hole would suffice for 6 x 6 and the concrete around it?

I have a Clark Flex 180. What do you think about a 6 x 6 at the head and two 4 x 4 for the ends? Or go with two 6 x 6 at each end for safety? I am ~270 pounds.

The eight inch hole will be okay for your application, a 6x6 will only be 5 5/8" and basically as far as anchoring, concrete just replaces the dirt you have removed with a more rigid material than shoveled in freshly packed dirt.
I think two 4x4's at the end would be okay
3.5 feet deep is plenty, the post would snap long before that came out of the ground under the type of load you are talking about here.

I hope you really enjoy your Clark

**nothermark** · 06-09-2013, 07:19

When you pick your timbers look at the end grain. You want something roughly symetrical around the center of the log it was cut from. Otherwise it will probably warp in one direction.

**kc0qnx** · 06-09-2013, 08:15

we pack white rock or gravel around the posts we set and tamp them in solid. when you have 3-4 ft of a 6"post in an 8" hole in the ground, it's not going anywhere. Like someone said before, put a few inches of rock in the bottom of the hole to prevent rot.