concrete for fence posts

Eric_Phillips · Aug 6, 2009

I am putting up vinyl fencing from Ramm fencing. they want concrete in each hole. I was at Lowes and they have fast setting concrete that says it can be used dry in a post hole. Then there is the standard concrete. The quick set is almost twice as much as the normal stuff. Can I put the normal setting stuff in dry or do I need to mix it. I am looking at 69 posts and the 80lb bag of the normal stuff says about 2.5 bags per hole. That is 172 bags or 13800lb of concrete. Any tips on doing this myself? Should I rent a portable mixer and so it all wet?

Egon · Aug 6, 2009

My back aches just thinking of that many bags of cement.

Is it possible to get a small ready mix truck out and have a drive by the hole filling??

The regular stuff can go in dry and then add water later. It will set up.

J_J · Aug 6, 2009

Eric_Phillips said:
I am putting up vinyl fencing from Ramm fencing. they want concrete in each hole. I was at Lowes and they have fast setting concrete that says it can be used dry in a post hole. Then there is the standard concrete. The quick set is almost twice as much as the normal stuff. Can I put the normal setting stuff in dry or do I need to mix it. I am looking at 69 posts and the 80lb bag of the normal stuff says about 2.5 bags per hole. That is 172 bags or lb of concrete. Any tips on doing this myself? Should I rent a portable mixer and so it all wet?

Just pour the dry stuff, straighten up the post, pack a little. The ground moisture will cause it to set up. Add a gal of water to the hole if you want. A little rain wouldn't hurt at all. It is much easier to put the bag on the ground and slice the top, and pour in the hole. Lot less work.

2 1/2 bags @ 80 lbs sounds a bit much.

bpattie · Aug 6, 2009

I have seen an awful lot of vinyl fences go up without concrete, at least here in Colorado. they just tamp the hole. I have put up several miles of wooden post fences and have only used concrete in the corner and periodic h brace.

pickngrin · Aug 6, 2009

I agree that 2.5 80lb bags per hole seems like a lot. As I recall 4x4 posts 24" deep into 8-9 inch holes required 1.5 - 2 60lb bags.

I do like the fast setting concrete and have had good results with it, but it is expensive. JJ's idea of pouring in the dry stuff and letting it set up with ground moisture is intriguing. If you've got 69 holes to do why not try a couple using this method and see if you're satisfied with how they set up? This would save a lot of labor and $$.

Duffster · Aug 6, 2009

Use the normal stuff and pour it dry. Unless you have EXTREMELY dry soil you will have plenty of moisture in the soil for the concrete to set.

J_J · Aug 6, 2009

Has anybody had extra cement laying around? I put 4 bags under some wood with a tarp over it, and later when I wanted to use some of it guess what, it was solid. I learned later to put the bags of cement in plastic bags and duct tape closed.

Therios Pendragon · Aug 6, 2009

I never thought that regular cement would set up... but I have had those stupid bags that were solid after little time here in the Oregon humidity...

So now for the stupid question of the day... what is the difference between the two types. I always wondered about the pour and then wet kind and how it physically differed.

So I can't help but to wonder if there were any issues with regular concrete curing with very little moisture... I know those bags that I find aren't very solid... certainly even with a little rain, those bags are NOT as solid as properly mixed cement.

Mike120 · Aug 7, 2009

With vinyl posts you do not want to rely on rain/ground water to set the concrete. Pour water in the hole before and after the concrete and "poke it with a stick" to make sure. Otherwise, when you thread your rails in the posts will crawl all over the place. Also, you may want to set your posts about an inch deeper than where you want the tops. After you've got the concrete in the hole, lift them slightly to get some concrete under the post. This will keep them from sinking later on.

After they've set overnight you can go through and adjust them up to level. You can only go up....down is not an option. If you lift one, pour a cup or so of dry concrete into the post with a bit of water. That will put something under the posts to keep them level. Concrete does not bind to the vinyl...that's why it is very important to put it in the hole...it's about making a stable hole. 80# is a good amount. Don't bother with the expensive quick set....in fact find a lumber yard...usually any place is cheaper than Lowes.

I've got over a mile of vinyl fence. If you do it right it will last a lifetime, if you do it wrong you'll spend a lifetime messing with it. Call Lee over at Triple S Vinyl Triple S Vinyl Sales, Inc. and get his marking cable, a notching tool, and a pair of rail removers. It will make the job a lot easier. By the way.....Ramm Fence has good products, but you can get vinyl a lot cheaper elsewhere.

Eric_Phillips · Aug 7, 2009

Thanks for he suggestions. I will use the normal stuff and add a little water. Mike I liked your suggestion to put the concrete in the hole and them pull the posts up to level but my posts have a square hole about 6-12" from the bottom. I am afraid the concrete will get in the hole and create a key not letting me raise the post. I am going to try to get them the correct hight to start with

Now for another question. I drilled some holes and some of them are just caving in. The soil is so sandy and rocky that is just doesn't hold together. Once I get the hole deep enough it will probably be 3-4 feet across. Could I just drop a sonotube, not sure of the spelling, in the hole then pack dirt around that and pour the concrete inside with the post?

QRTRHRS · Aug 7, 2009

When I dump a dry bag of cement around a post, I like to poke around it with a piece of 1/4" rebar. Gets the air out and gets it settled into all the little voids much better than a standard tamping bar.

Egon · Aug 8, 2009

You should be able to do that.

Mike120 · Aug 8, 2009

Eric_Phillips said:
Thanks for he suggestions. I will use the normal stuff and add a little water. Mike I liked your suggestion to put the concrete in the hole and them pull the posts up to level but my posts have a square hole about 6-12" from the bottom. I am afraid the concrete will get in the hole and create a key not letting me raise the post. I am going to try to get them the correct hight to start with

Now for another question. I drilled some holes and some of them are just caving in. The soil is so sandy and rocky that is just doesn't hold together. Once I get the hole deep enough it will probably be 3-4 feet across. Could I just drop a sonotube, not sure of the spelling, in the hole then pack dirt around that and pour the concrete inside with the post?

I have no idea why they would put the hole there....I'd just cover the hole with a couple of layers of duct tape.

I've got a sandy loam but it holds together, I've never tried putting vinyl in shifting sand. A sonotube would be a possible, but $$, solution. Is it like that all the way to the bottom of the hole? Try calling Lee at Triple S, he seems to have a solution for most things related to vinyl and has shown me a few neat tricks that I've used successfully.

czechsonofagun · Aug 8, 2009

Tapped gravel is enough for a post, IMHO. I use concrete only for gates and corners. It is a horse fence I am talking about.

tommu56 · Aug 8, 2009

Mike120 said:
want to set your posts about an inch deeper than where you want the tops. After you've got the concrete in the hole, lift them slightly to get some concrete under the post. This will keep them from sinking later on.

I would be concerned with lifting the post to let concrete in bottom up here in the north water will eventually get in there and freeze and brake post and concrete around it. Ive never set vinyl but for steel I put hockey puck (round concrete disk) under post 2~3" gravel then the concrete to just below grade.
This will provide footing (disk) drainage (gravel).

or fill post to the top with concrete after rails are in then it ain't going any were

tom

Cat_Driver · Aug 8, 2009

Speaking of letting bags sit out. I saw a retaining wall a guy built by just stacking cement bags. Over time those bags hardened solid, and when I saw the wall the bags still had paper on them yet they were solid. Strange but true.

I would think that perhaps you wouldn't have to every post to save some concrete. Depending on the soil do every other post or every 5-10 posts for stability.

twarr1 · Aug 8, 2009

I've done it both ways on my high-tensile fences - put in dry cement and add water, and use mixed concrete. In my experience the mixed concrete worked much better. I would recommend it at least for the corners and braces. When you consider the time and expense you're putting into it, doesn't make sense to take questionable shortcuts.
About those "set-up" bags of cement- that cement is ruined, not properly cured.

bota7800 · Aug 8, 2009

I put in flexible fencing from RAMM attached to pressure-treated posts. If you are talking about another product what I have to say may not apply. Really like the fence though - very safe and easy to maintain.

For the flex-fence, the instructions only call for concrete in the corner structure posts, the field posts go in dry. (If you have horses dry tamped is safer anyway) My fence was in Colorado - very dry ground - so I did not trust the dry mix technique - just my cautious approach. For the corners and gates I used a portable cement mixer driven by a generator. It was a pain moving both pieces of equipment but I would move it to a corner, cement in the 5 posts and move to the next corner. I would have preferred a PTO driven mixer, of course.

I bought pallets of 4000 psi quikrete and had it delivered with the posts. Several posts needed a lot more than 2.5 bags because I encountered many buried boulders so some of my holes were pretty big. I used Sonotubes in some of them, it worked OK.

Egon · Aug 8, 2009

Speaking of letting bags sit out. I saw a retaining wall a guy built by just stacking cement bags. Over time those bags hardened solid, and when I saw the wall the bags still had paper on them yet they were solid. Strange but true.

It's not uncommon to see bags of cement used for culvert rip rap.

wroughtn_harv · Aug 9, 2009

I mix the concrete. The reason I do so is I've been doing fencing for forty years or so. I've found that the dry set works best when doing a repair. I can take a twelve pound sledge and hit a post that was set dry set and the concrete will split top to bottom. The damaged post pulls right out. Mixed concrete on the other hand has to be dug out because it doesn't fracture so easy.

The toughest fence to set is in river bottoms out west where you have boulders and sand. The boulders mean the holes can't be done with an auger and the sand means you have to use water to keep it from caving in. If you're digging in sandy soil you water your holes as you go down and it won't cave in. Unless of course you use to much water.

Everyone wants to take the shortcuts. It's human nature. But every shortcut has its price. It would be nice to have a fence that looks like it was done right in the first place without all that work that doing it right takes.