digging holes for post and pier

[rogerbrickey]

I am in the thinking stage of building a cabin, wondering how to dig holes 48" deep for the pier. Any help will be appreciated.

[jdew]

I'd rent a power post hole digger.   Or hire somebody to do it for you.  A few years back I paid a guy $15/hole for a project I was working on.

[rdpecken]

We rented a 1-man post hole digger for ours.  It had a 12 inch auger, which actually wobbled out to about a 14 inch hole.  In the bottom 6 inches of the hole, we widened it to 16 inches for our footings.

This had a gas engine, and a single axle that you wheeled it around on.  You place it over the spot and lower it into the ground to dig.  Each hole took about 5 to 10 minutes at our place, depending on how many rocks we ran into.  We only had to go 2 feet deep.  To go deeper, we would have had to stop the auger while it was in the hole, and disconnect/reconnect it to a different mounting point.

[Bellla]

We are also in the planning stage (still!!!) but have the problem of extremely rocky soil.  Would the amount of rock make a difference as to whether you could use an auger?

Bellla

[jraabe]

Remember that the goal is to get down to solid bearing with a surface that will support all the loads you will carry and not move when frozen.

If you are hitting solid rock (or well drained broken rock) you may have met both conditions fairly close to the surface. Frost depth is important in expansive clay soils. If your soil won't expand you may not need to be down 48".

This may not convince the inspector however.

[RAB]

Bellla:
Often times digging in unfamiliar soil (and other places too) is a journey of discovery. If a hand auger is inefficient you can go to a bobcat mounted auger and if that doesn't work you can go to a backhoe with a rock thumb and if that doesn't work you can go to an excavator with a hammer and rock thumb.
This is a very familiar journey in my area and the path to the bank gets used more than first anticipated.
Fortunately as John has suggested some codes allow shallow footings/piers when encountering rocky soil or bedrock.

Ryan B

[Amanda_931]

I've got a tractor mounted auger (12-inch) have used it for both post holes and footing/foundations.

The hand-held ones CAN be pretty dangerous.  If they hang up on something, e.g. rock or root, they'll sling you instead of dirt.  Charlie Daniels of the Charlie Daniels Band broke an arm with one.

I've done quite a bit of damage to a thunb with an air-rachet, don't think I'd want to multiply that by a gas engine's power.

Hope you don't have to go down that far.  With the tractor, deeper than the distance of the auger?  it gets done with one of those 16-pound digging sticks, either scooped out by hand or by what, in my part of the country is never used as a post hole digger.

I've watched pro fence builders put in posts in next to no time, tractor with their attachment, truck with the poles.  It looks WONDERFUL!

[kenhill]

We used shovels and a pry bar to dig 12 holes to 40-48 inches deep.  Only took 1 day with a family of four (2 dug the first 2 feet and the others dug as far as they could go.

Builds character and appreciation for your cabin!

[murphish]

Remember that the goal is to get down to solid bearing with a surface that will support all the loads you will carry and not move when frozen.

If you are hitting solid rock (or well drained broken rock) you may have met both conditions fairly close to the surface. Frost depth is important in expansive clay soils. If your soil won't expand you may not need to be down 48".

This may not convince the inspector however.

So, How DO you convince the inspector? On my land we can only go down 10" to 20" before hitting bedrock. Right now there's a mobile home on a concrete pad, no problem, but a foundation is out of the question. Any suggestions?

[jraabe]

You should talk to the inspector. If the mobile does fine with a shallower foundation it is likely allowed for your situation as well.

Mostly these are reasonable people (with exceptions, of course, there are jerks in any field).

[Bellla]

Ryan, thanks for giving me some new ideas.  The guy who did the soil test on our property used a bobcat and has an excavation business.  I bet he would have the equipment to take care of those pesky holes (unless KenHills family wants to come by to build some more character!  Amanda, thanks for the heads up on the handheld augers - as rocky as our soil is it would definitely be a bad idea to use one.

Bellla

[rogerbrickey]

Many thanks for the ideas

[cre90602]

easist way to do them rent a bobcat skid loader with an auger attachment they have extensions if you need to go deeper the auger length no kickback you can also use the bucket for odd stuff on site try to rent on a saturday most rental yards are closed sunday and will let you keep the machine sat and sun you just have to watch the hour meter

[keyholefarmhouse]

Know anyone with a PHD?

[glenn kangiser]

That was very deep, Keyhole. :-/