Fence post installation? Concrete vs packed gravel

[Elite]

Hello everyone,

I am building a wooden privacy fence in northern Alberta. Our soil is a few inches of top soil and then clay. I have been researching and reading a lot of different ways to set the posts. I am planning to go 4 feet down and the fence to be 6ft tall.

Sounds like the concrete actually retains water when then wood shrinks and can rot the 6x6 out. It is also prone to frost heaving. Gravel let’s the water drain away and makes replacing fence post down the road easy.

I do plan on adding 2x 8 foot gates to make one large gate for a RV. The other end of each gate will be supported by a trailer jack with a large wheel. But I am worried gravel around a post won’t support the gate posts and corner posts

I am looking for some advice on which route I should go. I like to think projects through and utilize the best technique to not have to re do them down the road.

Spoke with a few local fencing guys and they seem to all have different ways. One company suggested only 3’ deep and 2 bags of concrete per post? Frost line is 4ft

It’s also interesting that the power companies around here use crushed gravel on there large power poles?


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[Elite]

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[Dunndm]

As a contractor I’ve only ever used concrete to set post. For “optimal” long lasting post put some plastic on the base of the post that will be in contact with concrete/dirt. If your going 6’ high go at least 24” down


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[FLATHEAD]

Currently putting up a larger, fenced in area around my chicken coop
using 4x4's and t-posts.
The 4x's are 32" in the ground with concrete.

 

[hunterjmj]

I've done both and prefer more of a road mix vs straight gravel. Road mix packs really well. I've also done concrete but had the posts sit on 4" of gravel to help with drainage. Not sure which way it better. I've pulled posts from our current place that were just put in dirt but were solid and guessing 20 years old or so. We'll be building some fence here and I'm just going to sink them in the dirt 3-4' and pack with the dirt.

 

[wnelson14]

Paint the post that goes in underground put a bag off gravel on the bottom, put your post in , set your post in concrete and make sure concrete goes above ground line and drains away from post. And the post will most likely outlive you.

 

[CRJR45]

No concrete ! When I built my horse farm I used road gravel , all the farmers do it , especially where you have the frost laws . Water travels through the road gravel , but with concrete it's forced down the out side of the concrete so when it freezes it lifts the concrete over time .

 

[cnelk]

Theres a fairly new product for setting posts in expanding foam. I havent used it yet but will give it a try on a next project

 

[KsRancher]

I haven't ever used gravel for backfill. It's always been concrete or the dirt tamped back in. I would think that the gravel would work. But I would hate to hang gates on post not in concrete. I would think 3ft would be fine for line post. I would go 4ft at a minimum for the gate and brace post. When building barb wire fence. We always put corners 5ft deep. Those are hedge with the dirt tamped back in. 3ft on a gate post isn't enough, unless the gate has a wheel

 

[KsRancher]

Theres a fairly new product for setting posts in expanding foam. I havent used it yet but will give it a try on a next project

Our local electric cooperative have using that foam here recently I have noticed.

 

[Bubblehide]

I have used galvanized post hangers in concrete. The hangers base, where the post sets, remain above ground to avoid moisture transfer. I also treat the base of the post.

Utility poles are treated, if they werent they would rot rapidly and or be eaten by termites.

 

[yfarm]

End of the post always seems to be the start of the rot, recently have started putting concrete in the bottom of the hole, letting set, then place post and pack around. Have replaced many rotted,termite eaten post set in concrete including cedar where the post end was in soil or gravel.
Dock posts in salt water always seem to rot first at the end deep in sand or mud, currently put 6” PVC over the 4” post, from as deep in the mud/sand as I can drive to over the top of the post and pour dry concrete filling the space between the post and pipe. Have some 20y/o posts still solid with this method, attach to the outside of the deck and no need for dock bumpers, boat goes up and down with the tide against the pvc.

 

[Elite]

Paint the post that goes in underground put a bag off gravel on the bottom, put your post in , set your post in concrete and make sure concrete goes above ground line and drains away from post. And the post will most likely outlive you.

If the frost line is 4ft deep would you go 4ft deep then some gravel and concrete all the way to the top? That would be a lot of concrete…


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[Elite]

I have used galvanized post hangers in concrete. The hangers base, where the post sets, remain above ground to avoid moisture transfer. I also treat the base of the post.

Utility poles are treated, if they werent they would rot rapidly and or be eaten by termites.

The 6x6 posts I am using are pressure treated as well


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[Ucsdryder]

Hello everyone,

I am building a wooden privacy fence in northern Alberta. Our soil is a few inches of top soil and then clay. I have been researching and reading a lot of different ways to set the posts. I am planning to go 4 feet down and the fence to be 6ft tall.

Sounds like the concrete actually retains water when then wood shrinks and can rot the 6x6 out. It is also prone to frost heaving. Gravel let’s the water drain away and makes replacing fence post down the road easy.

I do plan on adding 2x 8 foot gates to make one large gate for a RV. The other end of each gate will be supported by a trailer jack with a large wheel. But I am worried gravel around a post won’t support the gate posts and corner posts

I am looking for some advice on which route I should go. I like to think projects through and utilize the best technique to not have to re do them down the road.

Spoke with a few local fencing guys and they seem to all have different ways. One company suggested only 3’ deep and 2 bags of concrete per post? Frost line is 4ft

It’s also interesting that the power companies around here use crushed gravel on there large power poles?


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Use galvanized hangers. Putting wood in concrete is like putting it in a bucket of water.

 

[CRJR45]

Theres a fairly new product for setting posts in expanding foam. I havent used it yet but will give it a try on a next project

It's crazy expensive .

 

[Pony Soldier]

I really appreciate this as I don't have any of those issues. Bedrock is at inches to 3 ft. Things don't rot as they are frozen from sept till june. 70 year old posts rot from the top down.

I have one month to put in posts- last two weeks in june and first two weeks in July. Before that it's frozen and after that it's concrete.

Thanks again folks.

 

[*zap*]

a cup sitting on a saucer is the effect you want to avoid if you use concrete. Place clean gravel a few inches in the bottom of the hole then place the post and then 6" more clean gravel around the post. Any water that goes between the post and the concrete will drain out...if the concrete goes under the post the water gets retained next to the post. I would do the same thing if I used ab3 instead of concrete..since it can set up hard after if gets wet. You can also use a dry concrete mix which will eventually set up hard from moisture...that is simpler than mixing wet concrete.

 

[Ucsdryder]

I really appreciate this as I don't have any of those issues. Bedrock is at inches to 3 ft. Things don't rot as they are frozen from sept till june. 70 year old posts rot from the top down.

I have one month to put in posts- last two weeks in june and first two weeks in July. Before that it's frozen and after that it's concrete.

Thanks again folks.

Would all that freezing and melting cause issues with the wood? Wood never seems to do well sitting in water but it sounds like it’s not an issue there. I’ve replaced lots of wood posts that rotted from sitting in bathtub type cement. It’s a royal pain in the ass.


Are those 70 year old posts sitting in concrete?

 

[Elite]

a cup sitting on a saucer is the effect you want to avoid if you use concrete. Place clean gravel a few inches in the bottom of the hole then place the post and then 6" more clean gravel around the post. Any water that goes between the post and the concrete will drain out...if the concrete goes under the post the water gets retained next to the post. I would do the same thing if I used ab3 instead of concrete..since it can set up hard after if gets wet. You can also use a dry concrete mix which will eventually set up hard from moisture...that is simpler than mixing wet concrete.

Thanks for the suggestion. If that concrete is 6” above the gravel base and above the frost line would that cause issues with frost pushing out the posts?


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