PDA

View Full Version : Setting fence posts--put the concrete in dry?



Matt Meiser
05-09-2011, 2:02 PM
I'm building a small picket fence to screen an AC unit. Its only about 3' high, L-shaped, 54" on each side, with 3 posts. I read somewhere you can just dump dry concrete mix in the holes around the posts. Does this really work?

Lee Schierer
05-09-2011, 2:23 PM
I've heard of the same thing, but have never tried it. It probably depends upon how wet the ground is. Right now it my back yard a post hole would fill with water as fast as you can dig it. I know that concrete will set up in the bags after a while if they are stored in a damp location for very long, so I would guess the ground dampness would make it set up as well. How strong the non-water method might be as compared to the manufacturers instructions is anybody's guess. Pouring dry concrete mix into a hole will create clouds of concrete dust.

Scott T Smith
05-09-2011, 3:09 PM
I'm building a small picket fence to screen an AC unit. Its only about 3' high, L-shaped, 54" on each side, with 3 posts. I read somewhere you can just dump dry concrete mix in the holes around the posts. Does this really work?

I can personally attest that this works. As you get rain the groundwater will seep into the concrete and cure it. You can also pour the mix in and dump some water into it and mix it a bit to accelerate the process.

Don Jarvie
05-09-2011, 3:11 PM
I've never heard of just putting the concrete in and not add water. I know you can put the post in, add the dry concrete and then add water and just poke it with a stick to get the water around.

Bob Riefer
05-09-2011, 3:18 PM
I do this for line runs, but that for gates and corners I like to mix and pour.

For a fence as small as you're doing, I honestly wouldn't even use conrete at all if it were my place, but some poured in dry mix is easy enough to do, it can't hurt.

Matt Meiser
05-09-2011, 3:24 PM
I bought it already so I might as well use it. As wet as it is here, it will get plenty of moisture. I expect they'll fill with water like Lee's would. There was standing water 30' away yesterday--mostly dried up today, but still very wet.

Chris Padilla
05-09-2011, 3:49 PM
The concrete mix should say right on it if it can be done this way. Quickrete make a "fence post" mix that you dump in dry...add water...you're done.

John Fabre
05-09-2011, 4:01 PM
I put up 300' of fence ten years ago using Quickrete some with water, some without. Both worked very well, but the Quickrete is eating away at the wood now. If I was to do it over, i'll use pea gravel, in your case it doesn't need to be sturdy.

Ben Hatcher
05-09-2011, 4:12 PM
I've always been told to put a few inches of gravel in the bottom of the hole first, then the post, then the dry concrete, then some water. The gravel keeps the bottom of the post from sitting directly on a wet surface. Obviously, if the ground is saturated it'll be wet no matter what. But in times when the soil is simply moist, this will reduce rot.

Jerome Stanek
05-09-2011, 5:50 PM
Here you pour a layer of concrete in the bottom of the hole and use dirt to fill around the post. That way the frost doesn't have any thing to grip to and lift the post.

Mike Cruz
05-09-2011, 6:22 PM
Yes, Matt, it works just fine. Would I do it for something structural? No, but for fence posts it works. I've done it successfully.

Joe Angrisani
05-09-2011, 6:56 PM
Matt.... I would actually suggest not doing what Jerome suggested in post #10. You do not want the end of a fence post encapsulated in concrete. Put gravel in each hole so the bottom inch or two of the post is set in gravel. Then put the concrete above it, like Ben said. That way any moisture can drain off the wood instead of the concrete acting like a cup that holds water from above.

Norman Hitt
05-09-2011, 6:58 PM
I've never tried it that way, but for the last 45 years I've filled the hole about 3/4 full with water, and then dumped the dry mix in and punched into it a few times with the shovel handle, and haven't had a failure yet. I doubt we would have very good results "Here" just putting the dry mix in because we just don't get much rain anymore.

The drought is so serious in West Texas currently, our city recently passed a new ordinance that became effective May 01, 2011 that states, "if you are caught watering on other than your assigned days, OR, at hours other than the designated night hours, the FINE is $2,000", (and they are very serious about enforcing it).

Jim Becker
05-09-2011, 9:02 PM
I have always done the "dry" method for using concrete with fence posts and it's usually only for corners and other posts that are either under stress or in ground that's less than ideal.

Mike Henderson
05-09-2011, 9:13 PM
I've done concrete in situ (dry) and you can have problems with it. You get the strongest concrete by mixing the proper amount of clean water with the concrete and by agitating it to make sure the aggregate is well distributed through the mix. When you do concrete in place, you risk putting too much or too little water in the mix. Too little water results in weak concrete. And if you put too much water, the aggregate will work through the mix to the bottom, especially if you do anything to stir the mix. You can also get dirty water into the mix which will adversely affect the strength of the mix.

For most fence posts, you'll get a strong enough mix. But for gate posts, or for posts where the fence direction changes (such as corner posts) I recommend you mix outside the hole and then put a stiff mix into the hole.

Mike

[I've especially had problems doing it the way Norman Hitt describes above. If you put a lot of water into the hole first, then dump the concrete mix in, the concrete and aggregate separate, with the aggregate going to the bottom and the concrete to the top. Also, it's almost impossible to keep the water clean so you get dirt incorporated into the concrete.]

Matt Meiser
05-09-2011, 9:22 PM
Well, at about 2' I hit water. Got them all in using the "dry" method and even got the pickets tacked in place. Waiting on some stainless fasteners to finish it up. I slightly miscalculated the length of the side so there's a little space at the end of the rails near the wall that wasn't supposed to be there but it won't be very visible, especially once LOMLjr's grapes really start growing.

Now I need to install edging and mulch.

194137

Dave Lehnert
05-09-2011, 9:51 PM
I never use water in the mix. Always dry. Never a problem with fence post etc.. Would not do it this way with a big project like a deck or larger fence. If you keep a bag of mix in a damp garage it will harden like a rock in the bag.
Mailbox post I use pea gravel. When a car or truck knocks it off and bust the 4x4 I can just dig out the gravel and replace. Very easy and no need to dig a new hole.

David G Baker
05-10-2011, 10:56 AM
Matt,
Several times I have had to remove posts that I set with dry concrete due to some remodeling and the concrete had adhered to the post just like a wet set. I have used dry set for posts in one of my pole buildings and have had no problems. It sure beats mixing concrete by hand.

Jerome Stanek
05-10-2011, 5:46 PM
I should have said to let the concrete harden before setting the post. That is code here for pole barn posts or you can use a solid concrete block to set the post on.

Bill Cunningham
05-10-2011, 9:59 PM
We always had a fairly high water table here. When I installed the sign for my business, I just dug a hole, it quickly filled with water, stuck in the 4x4 pressure treated main post, poured in a couple of bags of dry premix concrete, braced it, and let it set before adding a upper and lower arm to the post, and installing a 3' x 2' lighted sign frame between the arms. That was 22 years ago, and the sign is still standing and doing it's job today.. The water table has dropped more than 10 feet over the years, with the addition of municipal drains and sewers, not so sure the ground would be wet enough to do that today!

Norman Hitt
05-10-2011, 11:37 PM
I've done concrete in situ (dry) and you can have problems with it. You get the strongest concrete by mixing the proper amount of clean water with the concrete and by agitating it to make sure the aggregate is well distributed through the mix. When you do concrete in place, you risk putting too much or too little water in the mix. Too little water results in weak concrete. And if you put too much water, the aggregate will work through the mix to the bottom, especially if you do anything to stir the mix. You can also get dirty water into the mix which will adversely affect the strength of the mix.

For most fence posts, you'll get a strong enough mix. But for gate posts, or for posts where the fence direction changes (such as corner posts) I recommend you mix outside the hole and then put a stiff mix into the hole.

Mike

[I've especially had problems doing it the way Norman Hitt describes above. If you put a lot of water into the hole first, then dump the concrete mix in, the concrete and aggregate separate, with the aggregate going to the bottom and the concrete to the top. Also, it's almost impossible to keep the water clean so you get dirt incorporated into the concrete.]

I don't know if we are using a different mix or the soil is different, or the method is different, BUT, I sure wish you had been here when I decided to move a fence that I had put in 26 years before. It was a combination of 2 3/8" pipe at the two gates and two corners, and wood 4 x 4 posts in between. After digging two out, (which was making too large a hole, and they were extremely heavy to lift), a friend brought his company winch truck and we pulled them out. I wanted to salvage the metal posts for later use, but after an hour of the two of us beating on them with an 8# sledge hammer with NO luck at breaking the concrete off, we gave up and used a cutting torch to cut off the concrete encased portion and salvaged the shortened lengths for other use. There was no noticeable difference in either the look or strength of the concrete on the posts between the bottom and the top of the concrete. Only the bottom 2" of each post was bare of concrete because I always jam them into the ground to hold them in place while filling with the mixture and then adjusting them vertically.

Maybe it is because the soil is so dry here normally, but although the landing strip runway we built at a hunting camp in 1976 has been unuseable for several years, the 20' length of 4" pipe we buried 42" deep with the same concrete method to hold the Wind Sock is still standing tall and straight even after all the strong winds of all these years. Who knows why? :confused: (Maybe us Texans are just Luckier than you Californians)?:D

Note: No, I wouldn't pour structural concrete this way either.;)

Doug Sewell
05-11-2011, 11:27 PM
If you need to keep working you can set it dry. Pack some tightly in the hole, add post, pack around post and keep working. At the end of the day add water and call it a day. This is the way I've done decks for years and never had any problems with the mix. It sure is faster than standind around and watching it dry.

Zach England
05-12-2011, 8:47 AM
I've always been told to put a few inches of gravel in the bottom of the hole first, then the post, then the dry concrete, then some water. The gravel keeps the bottom of the post from sitting directly on a wet surface. Obviously, if the ground is saturated it'll be wet no matter what. But in times when the soil is simply moist, this will reduce rot.

This is how my dad taught me to do it. That doesn't make it right, but the fence he and I built when I was probably 13 is still there.

Jerry Olexa
05-12-2011, 8:12 PM
I've done it dry but usually add water and then stir/mix in the hole...Ideally gravel at bottom of hole..Works well..

David Cramer
05-12-2011, 9:43 PM
I am in Macomb County Michigan Matt. The city code "encouraged" me to use nothing but pea gravel for my posts for my 10' by 17' deck.

Put pea gravel in the bottom first to keep it off the soil so that it can dry. Then fill up 1/4 of the hole and hold it plumb. Then take a 2 by 4 and smack it down on the pea gravel which will lock it tightly around the post. Do it a couple more times as you work your way up and shazaaammm!, it works.

We have to go down 42" where I live and with the pea gravel it is locked in pretty good....aka the free standing deck doesn't move. Just my opinion on how to do it and I wish I had done my pergola the same way, but that was a few years earlier:).

David

p.s. Yes, if you are going to put dry concrete in the hole, that works also and works well. I'm just trying to help the next guy in about 30 years from now:), but hopefully longer:D.

Rick Prosser
11-21-2011, 11:52 PM
I should have said to let the concrete harden before setting the post. That is code here for pole barn posts or you can use a solid concrete block to set the post on.

When the crew put up my pole building shop, they dug the holes, dropped a concrete "puck" in the hole, set the post, and added a bag of dry 'crete. Then filled in the hole with dirt.