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.