Putting up a fence

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swimmer_spe

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My backyard is kind of like a front yard. Due to the fact that I am on a corner lot, and the road is on 3 of 4 sides of my house, and that my driveway is on the back yard, not the front yard, it makes for an odd thing.

Currently, my backyard only has a fence that separates me and my neighbour. I plan to close in the other 2 sides in the spring. My question is: I plan to have a 6 foot high fence. How long do the posts need to be to be deep enough that it will not lean over the first windstorm or snowfall?

I am in Canada and we get lots of snow. How deep should the post be in the ground?
 

pjones

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My backyard is kind of like a front yard. Due to the fact that I am on a corner lot, and the road is on 3 of 4 sides of my house, and that my driveway is on the back yard, not the front yard, it makes for an odd thing.

Currently, my backyard only has a fence that separates me and my neighbour. I plan to close in the other 2 sides in the spring. My question is: I plan to have a 6 foot high fence. How long do the posts need to be to be deep enough that it will not lean over the first windstorm or snowfall?

I am in Canada and we get lots of snow. How deep should the post be in the ground?
When I built my 5’ fence (top 12” is lattice) I used 8’ posts and I think I dug them down 2’ to 2.5’ into the ground. Made for a solid fence for the last 10 years. I tried to get them as deep as possible while leaving myself the ability to level all the panels when I was done. For that reason I didn’t burry them all 3’ down. If I did then I wouldn’t be able to adjust for roots and grade changes.

My ground is 12” soil followed by about 12” soil and clay mixture I think it was after that 2’ mark it becomes pretty much solid clay. I’m also in Canada but right down close to the water, not much snow in these parts. Close enough that the water table is roughly only 12” below grade. And if the tide is high with a rain storm then it’s not uncommon for the water to sit at about 1” below grade. I know because I dug a trampoline into the ground. 14’ round and 5’ deep. Best toy on the back yard, kids jump on it year round. I let the pit flood over winter because there is no way it will freeze that deep and it means I don’t need to pull the pump out over the winter. Sometimes the kids get a fun surprise when they jump on the trampoline on a wet day with a high tide. My son loves it.... anyways back to the topic at hand...

I used a gas post hole digger that was 1” diameter larger than the post. But wasn’t able to use it because the soil was so heavy with clay as we got deeper into it. It would bind in the clay and spin two grown men right round. Thing was a beast in its prime. Also the tree roots made it a poor choice of tool. We ended up digging with shovels.

The posts I used were 4x6” treated lumber with post caps on top. No signs of rot. 5’ cedar fence panels also holding up well. Except for one spot that I didn’t allow for the roots to grow underneath very well. The one fence panel has a noticeable bow in it from the roots pushing up on it. The posts are holding strong though so thinking about it now it’s quite impressive. That’s a lot of upward pressure being put onto each post.

After installing the panels and letting the concrete cure (post haste 30 minute cure or something similar works well) I cut the post tops about 4” above the fence height. I’m trying to recall how much came off the top. I don’t think I cut more than a foot off the post in any spot so that would put me in the 2 to 2.5’ deep range... the numbers are adding up. It has been 10 years now but the details are starting to come back. I’ll have to take a closer look tomorrow, or whenever I remember, when the light is better.

If you think you might have animals, raccoons, possums, skunks, etc, you may want to take this chance to dig a trough under the fence panel and poor a line of concrete, place paving stones, or dump crushed gravel down to deter digging. I wish I would have done that at the time but can’t be bothered to unscrew the panels now and revisit that project.
 

Jeff Handy

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Your city or jurisdiction should have guidelines about fence post depth, fence height, fence style, materials, set backs from property lines, and probably more things they want to control or charge you for.
 

Skeezix

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When I set my fence posts I used 4x4s that were 8 feet long and I set them 2 feet below the surface and surrounded them with concrete. That was 20-some years ago and they haven't budged.

Or rotted. I live in Colorado at 4600 feet and do get snow during the winter.
 

Jeff Handy

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Fence post correct depth will vary with local codes, sometimes based on frost heave issues.

Also, fence height and style, and soil type and moisture level, will influence depth needed.

A taller fence needs deeper posts.

A solid fence will have much more wind load than a shadowbox or open style of fence.

Gate posts and corner posts should be especially strong and deep, they are under extra stress.
Choose posts without large knots or splits or defects.
They will be hard to pull out if they fail.
And you will need to pull or dig them out, you can’t just put a new post a little bit over from the old location, as you often can when replacing a line post.
 

pjones

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Fence post correct depth will vary with local codes, sometimes based on frost heave issues.

Also, fence height and style, and soil type and moisture level, will influence depth needed.

A taller fence needs deeper posts.

A solid fence will have much more wind load than a shadowbox or open style of fence.

Gate posts and corner posts should be especially strong and deep, they are under extra stress.
Choose posts without large knots or splits or defects.
They will be hard to pull out if they fail.
And you will need to pull or dig them out, you can’t just put a new post a little bit over from the old location, as you often can when replacing a line post.
Good information, specially about the frost line. That will move your posts in no time flat. I believe our frost line is 12" if I recall correctly from a project a friend recently did. I’m not sure how deep below it you are supposed to be so , as Jeff recommended, checking local codes would certainly be beneficial.

What’s a line post?
 

Jeff Handy

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A line post is a fence post just holding up fence sections as part of a long run.

Not at a corner, or end, or at a gate.

So if a line post fails, you can sometimes leave the concrete and part of the old post in the ground cut flush with the soil.
Then put a new post right next to it, and adjust the fence panels to work with it like that.

But a corner post, end post, or gate post usually has to be pulled up or dug out.
The new post usually has to go in that same exact spot.
 

nealtw

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1/3 of the post should be in the ground or at frost depth which ever is deeper. For a 6 ft fence we get 10 ft posts,
If you are setting them in concrete you can go deeper with concrete for frost depth and still use 10 ft.
 

swimmer_spe

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1/3 of the post should be in the ground or at frost depth which ever is deeper. For a 6 ft fence we get 10 ft posts,
If you are setting them in concrete you can go deeper with concrete for frost depth and still use 10 ft.
.

I am concerned of how deep my frost line is. I know when they dug for my garage, they only went down 2 feet.
 

bud16415

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Most of the time frost and fence posts isn’t a big deal. If the ground freezes it expands and it needs something to push against. If the posts are just placed in soil all you have is the area on the end of the post to push against and if it does lift it a little the fencing will flex enough and when it thaws it goes back down. I built my whole deck free floating and not attached to the house. It moves up and down a little but doesn’t do any damage. On the other hand I have a little mud room that was a covered porch at one point and it is attached to the house. The one wall floats with the frost if it gets really cold and the house doesn’t move. It causes a door to bind sometime.


With a fence I would be mostly worried about wind loading and just stability with usage in general. Gates need to be deeper IMO. If you are renting a PHD it is pretty easy to go down 3’ I have a two handle manual PHD and have done lots of holes 2.5-3’ deep it just takes more time. if you get into a big root and want to skimp on one post its not a big deal.


I have a DIY homemade tamper big chunk of steel welded to a pipe and when I fill the hole I tamp it good every few inches. With PT posts I think that works just as good as pouring a bag of ready mix in the hole and if you ever have to replace a pole it makes it a lot easier.


Our frost depth is 4’ but that might only be once every 10 years. I don’t know anyone that plant fence posts that deep.
 

Jeff Handy

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I have occasionally set posts in a sand and small gravel mix similar to what you use as paver base.

Tamp it down with a long skinny heavy tool which is like a five foot screwdriver.
Just add a little more mix after a month or two of final settling.

As bud said, easy to pull a post if needed.
I only use treated posts, and I buy them well in advance, and buy several extra.
I let them dry, and return the ones that warp or twist the most.

In the past, I have had new cedar posts rot off at the ground in just four years, when set in concrete.
 

nealtw

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I have occasionally set posts in a sand and small gravel mix similar to what you use as paver base.

Tamp it down with a long skinny heavy tool which is like a five foot screwdriver.
Just add a little more mix after a month or two of final settling.

As bud said, easy to pull a post if needed.
I only use treated posts, and I buy them well in advance, and buy several extra.
I let them dry, and return the ones that warp or twist the most.

In the past, I have had new cedar posts rot off at the ground in just four years, when set in concrete.
Posts always rot at the ground level first, 6" of peel and stick centered at ground level will add year to the life of a post

frost heave???
 

nealtw

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For a straight fence we found this to be fast and straight
plant the corner posts first and the run a string near the top.
1. brace the top with the brace in line with the string.
2. with a level, make the post plumb and stake the bottom. fence posts..png
 

swimmer_spe

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For a straight fence we found this to be fast and straight
plant the corner posts first and the run a string near the top.
1. brace the top with the brace in line with the string.
2. with a level, make the post plumb and stake the bottom. View attachment 23354
I wouldn't have thought of the lower part. I also would have the post sitting on the bottom of the hole.

Thank you. Now I can do it right.
 

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