Fence post installation? Concrete vs packed gravel

[Trochu]

Originally Posted by CBintheNorth

4x6 PT post, 8" hole, 2" of rock at the bottom, concrete all the way up.
Make sure your concrete is at least 1 inch above final grade, and sloped away from the post in all directions. My fence is 15 years old and the posts are as solid as the day I put them in.

Your post holes are only 8" deep?

That wouldn't even be through the topsoil here.

[calgarychef]

I had a neighbour who was an ex military carpenter. We built a fence together and he explained how concrete and wood are bad combinations. We used road crush gravel and pounded it in around the posts. We were careful not to get any dirt mixed in while pounding and added water periodically. Those posts lasted decades, they’re still there.

[jungleboy]

Originally Posted by Dick284

Most people get wooden post installation wrong IMO.

Start with about 3-4” of pea to 3/4 gravel(not crush) at the hole bottom(you’ll have to auger a bit deeper depth) set your post, and square it up. Then dump 1/2 of a bag of dry ready mix, then pack in the clay(mechanical tamped) till 3/4-7/8 of the way full then add the other 1/2 of the ready mix. Top what’s left with more clay or top soil.

Resist the urge to use wet cement with posts. That’s what degrades the wood.

Dry ready mix draws moisture out of the soil/earth and sets up like a honey comb type structure.

I used to work with a guy who did sign work and whenever we did posts for large signs this is how he did it, dry ready mix cement dumped in the hole and tamped . The ground moisture did the trick of setting the cement

[CBintheNorth]

Originally Posted by Trochu

Your post holes are only 8" deep?

That wouldn't even be through the topsoil here.

That would be hilarious the first time the wind blew.

I went 3 ft deep.

[EZM]

I have built many fences over the years and tried a bunch of different ways and finally settled on a compromise between the firm anchoring of concrete versus the permeability of crushed rock (20mm or 3/4" crush) to set posts.

I get a yard or two of 3/4" (20mm) road crush. I buy a couple bags of straight portland cement (not concrete mix but cement).

The proper ratio (shovel fulls is 3/1 assuming you are mixing conventional concrete) - I end up using 4/1 mix so it's not quite concrete but also is more bonded compared to straight gravel/aggregate.

Here's the drill;

I set the posts deep to at least the frost line (48") and sometimes will go 60" or more if the soil is not suitable (soft). Corners I always go 60"+

I dry pack the mix a couple shovels to half a wheelbarrow at a time and just pound it all the way around using a 2x4. My line levels are set up and I use a level for the other direction as I'm doing it periodically.

Basically I shovel from the pile of crush and shovel a scoop of portland cement with a 4/1 ratio and fill the wheelbarrow and then bring her over the hole for packing and setting DRY.

My theory is this provides some bonding to the aggregate, yet does not fill all the inclusions (holes) - so it ends up being permeable to water, yet the added cement binds the mix as I pack it in the hole DRY, a half wheelbarrow at a time, until I reach my desired depth - usually just at grade.

I double check my post alignments with a lazer at a few points after setting and packing my posts. A 2x4 can pack one side of the post easily and bring the post "over" to alignment quite a bit more than you would expect.

Once They are all packed tight and in perfect alignment - I run the water slow into the holes and allow the water to saturate.

I end up with solid posts, proper drainage and lazer straight posts that seem to last decades. Did my mom's place in the late 90's and the posts are still rock solid - even in wet areas of her yard.

Did another half dozen fencing jobs for myself and probably just as many to that in addition helping friends out as well. All great results with zero issue.

It's also way easier - doesn't need bracing - isn't a pain to mix concrete - and goes surprisingly fast.

[bcrams]

Anytime you put wood into the ground, it is going to rot eventually, answer to this is always staple tar paper to post. Posts will normally rot within the first 12” of ground. Once you backfill and tamp your ground around posts, just trim off the exposed tar paper and you’re good for life.