Plumbing a post that you're putting in concrete

[jbeall]

Hi All,

I'm working on <a href='http://loghomebuilders.org/starting-log-fort-kids'>a fort</a>, and one of the first things we'll need to do is plumb the posts we're planting in the ground. The plan is to dig a hole, put rocks in the bottom of give the post something to sit on (besides dirt), then pour concrete around it and make sure it's plumb while the concrete cures.

But, how do we plumb it and how do we make sure it stays plumb while the concrete is curing? I had a few ideas but wanted to input from others:


To plumb it, we can sink nails on, say, the north and west sides (or any two sides that are perpendicular to each other), hang a string with a weight on it off the nail, and then make sure that both sides of the post are aligned with these plumblines. We're using dimensional lumber for the posts so they should be flat on the sides, unlike a log.
To keep it plumb while it cures, we can use any bit of scrap wood or logs that are long enough to secure one end to the top portion of the post, and stake it into the ground on the other end. We'll have one brace like this on the North side, and another on the West side (or any two perpendicular sides).


Once the concrete has cured we'll pull the nails/plumblines and braces off.

Think that would work, or am I missing something? Is there another way?

-Josh

[Shark]

Use a couple long 2x4's for braces, nail one end to the beam, and the other end to some wood spiked into the ground so it stays secure.

Just use a 4' level to get them plumb, then nail the braces, check plumb again, then pour. Shouldn't be too hard.

[Kola]

Rocks/gravel in the bottom of the hole are for drainage. You dont want the post setting in water.( make sure you go deeper than the frost line for your area too).

for square posts these levels are cheap and simple. I have even used them on round posts. The orange one in the link should work just fine. The rubber band goes around the post and hooks back onto the level. This way, your hands are free to pick your nose and level it out. :)
http://hand-tools.hardwarestore.com/21-400-levels-post.aspx

[jbeall]

Rocks/gravel in the bottom of the hole are for drainage. You dont want the post setting in water.

Are you saying we shouldn't have the post setting on the rocks in the bottom of the hole? If so, what does the post set on?

[Kola]

you're OK, set your posts right on top of the gravel.

[StressMan79]

I like your plan. easier with plumb bobs than with a framing level. temporary bracing is what you should use for holding position during the cure.

-Peter

[d.ganschow]

I used to run a fencing business (not the swords) and I set a lot of posts. Previous posts are correct that some rocks in bottom allow drainage IF the soil underneath is porous. I used to dry set posts by placing the post in the hole and centering it where I need it (have a string line rigged up high on the posts from other objects or batter boards), then fill the hole with water about 1/3, then pour dry cement right from the sack into the hole and mix with a thin strong stick or a short piece of rebar by jamming the tamping rod into the hole all around the post mixing water and cement. Then repeat process with water and dry cement until hole is full being more careful toward the end to get the water/cement ratio closer so that the cement is workable.

I used to use just a torpedo level that I could slip into my back pocket while I filled the hole. If the cement is made stiff, it will hold the post with no support no problem. Cement will be nearly hardened in a few hours. Another thing I used to do was coat the sides of the post with roofing tar but NOT the base (this allows any water picked up from rain and sprinklers to drain out the bottom of the wood).

Hope this helps. Good luck!

Don G.

[Timber]

I have heard it rots the wood faster using cement versus just gravel and dirt and pack it. Seems the cement holds water.

[tanderson]

Just a few things I've learned about fencing...

There are a lot of people that want to get rid of decent boards because their posts are rotted, pressure washing makes them look new.

Pour enough concrete to be above grade, water won't settle in a high spot.

Dig deep in clay soils and use a masons line when erecting long fencelines.

In a repair, sometimes you can chisel the rough cut post out of the concrete and use a new pressure treated post. It's an option, but measure first.

A solid fence makes for good neighbors, on the western coast,

Call before you dig, if its a new fence

Thats about all I can add.