Do we need to use cement when installing sign posts?

LRy511June 10, 2013

My son is researching how to install sign posts for his Eagle Scout project. He is building a new sign for our church because storm Sandy knocked down the old one. He is planning on using 6x6 10' posts made of cedar so they won't rot. We live in New England so he has to set them four feet deep. He has found conflicting information regarding using cement or not. Some say cement is not necessary. Your opinions will be appreciated. Thank You.

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southerncanuck

Dig a 42" hole 10" round.

Throw a few shovels of stone into the bottom.

Set a 8" sonar tube into the hole cut flush with the top of hole. Back fill the hole.

Fill the sonar tube with cement working the cement with a broom handle to work out air pockets every foot of cement or so.

Level the top and set and level a steel post holder you may possibly find at Home Depot, a 6X6 post holder may be a special order, most sign posts are 4X4 only.

Let set for 24 hours.

Lag bolt the bottom of 6X6 into the post holder.

Yes you need to use cement. Without it the post will move from the wind. I bet there are many cemented posts still there after Sandy.

4 feet is too deep, have him call the building department to get the proper depth for your area, heck he might even ask if he needs a permit. Signage around here has become an issue with advertisers blocking drivers views, colour and size etc.

That would be a good lesson for him as well by speaking to the authorities. Where can he put it, how high, how wide, what colour, how large? Many jurisdictions have specific by laws to abide by.

Never set pressure treated material into cement or directly onto cement. Let him research as to why.

That's one big sign. He will need the entire troop to lift a post. I would say 4X4 is sufficient.

This post was edited by SouthernCanuck on Mon, Jun 10, 13 at 21:16

    Bookmark   June 10, 2013 at 8:58PM
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mike_kaiser_gw

Not to quibble but it's concrete, not cement. Cement is an ingredient in concrete like flour is an ingredient in bread. Ya wouldn't ask the baker for a loaf of flour...

    Bookmark   June 11, 2013 at 12:20AM
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klem1

â¢Posted by mike_kaiser (My Page) on
Tue, Jun 11, 13 at 0:20
Not to quibble but it's concrete, not cement. Cement is an ingredient in concrete like flour is an ingredient in bread. Ya wouldn't ask the baker for a loaf of flour...

So if not quibbling,what is your purpose in pointing out the regional use of a word?

    Bookmark   June 11, 2013 at 4:03AM
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snoonyb

Posted by klem1 (My Page) on Tue, Jun 11, 13 at 4:03

"So if not quibbling,what is your purpose in pointing out the regional use of a word?"

Obviously, somewhere other than your flour packaging facility.

    Bookmark   June 11, 2013 at 5:16AM
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LRy511

SouthernCanuck- Thanks for your assistance. My son went to the sign committee for our town and presented his sign with dimentions and all the necessary info. They gave him the parameters and the approval for the sign. He has learned a lot so far about town regulations and speaking to adults (you make the phone call and not e mail everyone ;) So what I gather is the post sits on top of the concrete and is not imbedded in it. How much of the post is in the ground? Just wondering if he should get a 10' or 8' post. He is doing all the work, I am just getting background so as to guide him. It is hard closing my mouth. Luckily, he will ask what we think.

    Bookmark   June 11, 2013 at 9:02AM
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snoonyb

In the alluded to method the post is not embedded in the concrete, or the ground. It instead sits in, saddled in a connecter, and bolted. If the straps on the connecter face the wrong way, the post will be subject to breaking at the bolt connections.They should be set to resist wind forces.

    Bookmark   June 11, 2013 at 11:29AM
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brickeyee

"set and level a steel post holder you may possibly find at Home Depot, a 6X6 post holder may be a special order, most sign posts are 4X4 only. "

Any of those "post holder" brackets are NOT designed for anything but a straight down load.

They have little resistance to lateral loads, like wind loading on a sign.

    Bookmark   June 11, 2013 at 12:47PM
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greg_2010

I second what brickeyee says.

I'm no expert, but I'd set these posts in the same way that you'd set fence posts, not deck posts.

    Bookmark   June 11, 2013 at 3:13PM
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southerncanuck

Yes concrete not cement, not a regional thing just late I stand corrected.

So Brickeeye you may be right concerning lateral loads so give the lad a tip on putting on cross members or digging 4 more holes to brace it. If there was an issue the building department would have pointed it out and not approved his plan.

Pressure treated wood can no longer be set into concrete. The interaction with concrete and cedar or PT lumber causes the lumber to hourglass at the point it contacts one another. Yes you set them on the concrete base now not in, never.

We are putting up a sign for goodness sakes, not erecting a deck 2 stories high..

I am so happy the youngster went to the municipality for guidance, a great lesson there, greater than learning how to put up a sign.

LRy,

I was so busy defending myself I almost forgot to answer your question, sometimes I just love this place, if people would put as much effort into helping, well........ We need to know the dimensions of the sign.

Any length 6X6 is far too heavy for an Eagle Scout to handle I believe but seeing the size of some kids today
Maybe not. Let us know the dimensions of the sign.

This post was edited by SouthernCanuck on Tue, Jun 11, 13 at 17:09

    Bookmark   June 11, 2013 at 4:58PM
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LRy511

Sign dimension is 75" x 36". Just scale wise - I think a five or six inch square post would look correct.
Your help is invaluable. Thank you.

    Bookmark   June 11, 2013 at 5:56PM
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LRy511

These are big boys. My son is 17 years old. Many of his friends will be helping as well as some fathers. If I make food for them, they will come.

    Bookmark   June 11, 2013 at 5:58PM
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homebound

Although I know the basics, you guys have confused the heck out of me.

I suggest pressure-treated lumber, not cedar. It will last longer. Make hole, crushed stone for the bottom, install post, add a couple more inches of stone, then set either in concrete or just use all soil. Concrete has the advantage of locking it in place nice and plumb with the proper bracing. (BTW, the concrete doesn't have to fill the hole.) Fill rest of hole with soil the following day.

Sonny might call the transportation department for some advice, too. More phone practice.

    Bookmark   June 11, 2013 at 7:01PM
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southerncanuck

A 4" post is all you need, 6" is overbuilding but will certainly look great. The height of the post can be the highest point of the sign with the sign framed between it. Place post caps on each post.

Good luck and send us a picture when complete.

And you are all most welcome.

    Bookmark   June 11, 2013 at 7:02PM
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brickeyee

" If there was an issue the building department would have pointed it out and not approved his plan. "

Maybe in the great whit north, but no in the USA.

"Pressure treated wood can no longer be set into concrete."

Must be a local thing.

The correct treated material and concrete mounting should provide more than enough lateral strength for wind loading.

The brackets are just a serious weak point wince they have little lateral strength,

A deck has a large downward load and a relatively small lateral load.

About the only thing NOT to do is end the posts in concrete creating a 'swimming pool' effect that traps water against the bottom of the post.

    Bookmark   June 11, 2013 at 7:57PM
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kudzu9

Further on the issue of using brackets, I second brickeyee's comments that they are a weak point. You will see them commonly used in inappropriate situations. What does this mean? If you look, for instance, at the Simpson Strong-Tie web site, they state:

"Post bases do not provide adequate resistance to prevent members from rotating about the base and therefore are not recommended for non top-supported installations (such as fences or unbraced carports)."

A large sign will have a surprising amount of windloading, and the likelihood of the installation leaning or failing at some point is pretty high if you install the posts using post bases.

    Bookmark   June 12, 2013 at 12:33AM
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LRy511

When you "backfill" --- would you use dirt or gravel?

    Bookmark   June 12, 2013 at 7:32AM
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snoonyb

Whether you are using the natural earth or concrete when setting the posts, placing 3-4" of gravel at the base of the post hole to allow moisture to drain away.
Using a 6x6 will require a hole slightly larger in dia. than a standard posthole digger.
After placing the loose gravel, setting and "roughly " plumbing the post, begin backfilling, in 6" "lifts" and tamping the soil. Adding a small amount of water between lifts will aid in the soil consolidation during tamping.
It's a common practice when using concrete to slightly dome the top.
In both cases, maintain the plumb and make sure the posts are square to each other.

    Bookmark   June 12, 2013 at 11:43AM
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homebound

Backfill with soil, compacting it as described above. You need to pack the soil well.

    Bookmark   June 12, 2013 at 1:31PM
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LRy511

A great big THANK YOU for all your help.

    Bookmark   June 12, 2013 at 8:35PM
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greg_2010

One of the advantages of using concrete instead of backfilling with soil is that you don't have to worry about whether you compacted the soil properly.
Loosely compacted soil will result in the sign shifting.

    Bookmark   June 13, 2013 at 9:46AM
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southerncanuck

So put the post into the concrete, I whole heartedly agree the lateral loads will not be an issue. I doubt the sign will be there for 25 years. Be sure to dome the top of the sonar tube for drainage and backfill the outside of the tube with the soil from the hole. I suggest wrapping the post where it comes into contact with the PT or cedar post with a small amount of Ice and Shield membrane where the post will contact the cement, I mean concrete.

    Bookmark   June 14, 2013 at 2:43AM
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brickeyee

" I whole heartedly agree the lateral loads will not be an issue."

It is in a wind free area?

Even a slight breeze will put a rather significant load on the post mounting in the earth.

Frost heave will not help things long term either.

    Bookmark   June 14, 2013 at 11:45AM
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rwiegand

Having installed several similarly sized signs and having lived long enough to have to replace them 20-25 years later I'd strongly urge you to give a thought to the next guy and not set the sign in concrete. Posts set 36-48" deep with tamped gravel around the base and then backfilled with tamped dirt as others have described will hold a sign up in any normal midwest thunderstorm (can't speak to tornados). When it comes time to dig them out however the concrete is a real PITA requiring an enormous hole and some backbreaking labor. Without concrete you can jack the old rotten posts out, widen the hole and be ready to install new ones with relative ease.

6x6 posts will definitely look better, though they may be structural overkill. Besides, scouts love lifting heavy objects (our troop told stories for years about the project that involved hand carrying 6" x 10" x 24 ft beams a half mile into the woods to build a bridge for a trail stream crossing.)

    Bookmark   June 14, 2013 at 2:17PM
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southerncanuck

Pickeyee,

I am sorry, I apologize, I am truly repentant, I misspoke, I didn't add the words, "with the post in concrete" after my statement.

You remind me of an old school British manager I once had, he was so busy correcting grammar and spelling he forgot to manage.

If you note the time of my post, around 2:30 AM, I wasn't as sharp as I should be, couldn't sleep that night, or most nights after a bout of chemo that day.

    Bookmark   June 14, 2013 at 10:39PM
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