Fence Question - Problem #1

[cabinetman]

I've got about 125' of board on board fence on the side of my house that runs from the front of the building to the back yard fence. It's 6' tall and there are 8' sections fastened to PT 4x4's in concrete 2' deep.

The first and major problem with the fence is that our ground is primarily sand, and during Wilma, with all the rain, two posts (on different sections) got loose from wet sand and they are leaning inward a few inches.

The fence is well within our property line at least by 12". The post holes were dug with a post hole digger, so the cement surround isn't all that wide spread. My first thoughts were to dig up the two posts and make a larger hole for the cement. That might be my only solution. Any other suggestions?
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[Uncle Cracker]

I'd dig a post hole just inside the current one, push the post upright (the soil to the outside should allow this without excavation), temporarily brace it in place with lumber, and pour concrete in the new hole you dug to the inside. After drying, remove the brace. If you need an uninterrupted dirt surface (for looks or plantings), leave the concrete pour shy of the surface a few inches, and cover back over with soil after the concrete has dried.

Some folks might suggest driving a PT wedge down into the soil to the inward side to prop up the post, but our Florida soil is probably not supportive enough for this to work, at least not in the long run.

[Daryl]

I am not a big fan of using concrete in soft soil as it always seems to work loose, crushed stone will do just as good a job. I have used underground bracing on posts and it kept them solid. You could use a pier form that looks like a cone and fill with concrete, the larger base would provide stability.

[Hellrazor]

I always bell the bottom of a hole out so the concrete acts like a plug. I have yet to see one pop out of the ground doing this.

[gjat]

Second on what Uncle says. Our soil is so "cohesionless" that crushed gravel will eventually move. If you can dig on the front and back of the post and pour additional concrete, that would be best. It only has to come up half way of your post embedment sort of making an upside down tee. Well tamp the soil above after conc is hard. It's a basic spread footer design where the soil on top of the concrete and wider base helps keep everything in place.

[crokett]

Cabman, I had the same problem with two posts on the fence at our old house. In our case it was a low spot between us and the neighbor and water liked to pool there when it rained. After I solved the drainage problem I fixed it using Uncle Cracker's fix but before I poured the new concrete I drilled into the old and hammered in some rebar.