Digging Post Hole In Shale: Coping w/Rocks?
(PeteCresswell)
Holes to be 2 feet deep, maybe 8" in diameter.
The zinger is that we're on a shale ridge and the probability of
hitting one or more good-sized stones is significant - based on
experience digging a dozen or so much larger holes to plant fruit
trees.
With the bigger holes there was room to move, but with the post
holes - unless they are made into bigger holes - there's not much
room.
First thing that comes to mind is a short breaker bar with some
sort of hardened tip to "make little ones out of big ones".
Alternatively, I could wimp out and call in somebody with one of
those backhoe-mounted drills....
Bottom line: is there a recognized strategy for dealing with
stones when digging a post hole by hand?
--
PeteCresswell
Larry
x...@y.Invalid says...
Concrete. Go as deep as you can, widen the hole to a
couple of feet, then buy a short section of tubing that
the post will fit into snugly. Drill the bottom of the
tubing to accept a couple of lengths of #4 rebar, and
drill the top of the tubing to accept lag bolts on each
side. Fill the hole with concrete and puddle the tubing
into place, let the concrete set for a week, then
install the post, shim it plumb and bolt it into place.
If you expect much force on the footing, lay a rebar mat
in the concrete to hold it together.
Sometimes a spot just doesn't deserve a hole. Many years
ago I used to build pole barns. If an owner wanted a
pole barn on solid rock, we would just form up a footing
and set the pole on top of the footing.
(PeteCresswell)
>Concrete. Go as deep as you can, widen the hole to a
>couple of feet, then buy a short section of tubing that
>the post will fit into snugly. Drill the bottom of the
>tubing to accept a couple of lengths of #4 rebar, and
>drill the top of the tubing to accept lag bolts on each
>side. Fill the hole with concrete and puddle the tubing
>into place, let the concrete set for a week, then
>install the post, shim it plumb and bolt it into place.
>If you expect much force on the footing, lay a rebar mat
>in the concrete to hold it together.
I was thinking 2" ID plastic pipe set in crushed stone and then
slipping 2" OD galvanized pipe into the plastic.
Wood would be a lot more friendly to work with though.
With the (presumably...) wooden posts in pipe set in concrete,
isn't there going to be a water pooling issue - where the posts
rot as they are immersed in rain water that accumulates in the
pipe?
--
PeteCresswell
Jim Elbrecht
>I want to put up a kayak rack that's built on two posts.
>
>Holes to be 2 feet deep, maybe 8" in diameter.
I have a steel bar that used to be a drive shaft. it still has the
splines in the end I pound with a hammer. It is some durable and
heavy metal. The other end was roughly pounded to a point-- and as
a bit of overkill, IMO, the previous owner welded some hardness to it.
I'll bet a junkyard would fix you up in short order.
my second choice would be a Harbor Freight bar-- and give it a
tempering on the business end.
If you've got shale, it flakes off pretty easy, just keep pounding it.
OTOH- I'd likely go Larry's route. Go as far as you can. If it
ain't deep enough make a concrete anchor. You're not building a
tower.
-snip-
>Alternatively, I could wimp out and call in somebody with one of
>those backhoe-mounted drills....
I'd be curious to hear of folks with experience on that. I suspect
that if your clamshells won't dig it, neither will an auger.
Jim
hub...@cccanoemail.com
>-snip-
>>Alternatively, I could wimp out and call in somebody with one of
>>those backhoe-mounted drills....
>I'd be curious to hear of folks with experience on that. I suspect
>that if your clamshells won't dig it, neither will an auger.
>Jim
I suspect he was meaning a jack-hammer type thing ( ? )
Which is what I'd rent if I had to go into rock - but I'd probably
look at ways to avoid going into rock first - like the other
people are suggesting.
John T.
Futility Man
> I suspect he was meaning a jack-hammer type thing ( ? )
>Which is what I'd rent if I had to go into rock - but I'd probably
>look at ways to avoid going into rock first - like the other
>people are suggesting.
I have a tractor mounted auger. It has hardened teeth that will dig through
shale, albeit slowly. Anything harder than that, if it must be dug, gets whacks
with a sharpened steel bar to break the rocks, then repeat the auger to roll the
chunks out.
I mounted some 4x4 treated posts for a billboard-type sign at the entrance to my
campground by boring some 18" deep holes and setting 6" PVC pipes in those
holes. Then slip the 4x4s in and fill around them with dry sand while holding
the posts vertical. Then add water to the sand and keep adding sand as it
settles. When the pipe is completely full of sand and packed, the post will be
quite solid but you can still pull it out with a tractor lift if you need to
remove it later.
--
Futility Man
(PeteCresswell)
> Then slip the 4x4s in and fill around them with dry sand while holding
>the posts vertical. Then add water to the sand and keep adding sand as it
>settles.
It sounds like, with the right kind of wood ("treated"... the
greenish stuff?) that rot from pooled water is not a problem.
?
--
PeteCresswell
Larry
x...@y.Invalid says...
> With the (presumably...) wooden posts in pipe set in
concrete,
> isn't there going to be a water pooling issue - where the posts
> rot as they are immersed in rain water that accumulates in the
> pipe?
I assumed you would use treated wood.
Futility Man
>It sounds like, with the right kind of wood ("treated"... the
>greenish stuff?) that rot from pooled water is not a problem.
I put a shovel of gravel in the bottom of the hole, then the plastic pipe, then
the concrete around the outside of the pipe. That lets any pooled water
dissipate out the bottom of the plastic pipe. If you go to Google Maps, put
35.348172,-84.307656
in the search box, then select Street View (click on the little man on the scale
bar and drag him to the A pointer on the picture), you can see the sign. You
may have to slide the picture so you're looking up the driveway to see it
clearly. It's been there for 7 years and I was on top of it tonight with a 16'
extension ladder (earlier this year I added an additional 4' section on top with
changeable letters) and it's just as solid as it was the day I put it in the
ground.
The overhead shot on the site is about 2 years old. The Street View shot is a
couple years older than that.
Or you can go to our Facebook page at:
http://www.facebook.com/pages/Hunts-Lodge-Motorcycle-Campground-Cabins/77449729803?v=wall
and see the sign with the added section. It's still very solidly in the ground.
The signboards both are made to flap in the breeze, which takes a lot of load
off the uprights.
--
Futility Man
(PeteCresswell)
>I put a shovel of gravel in the bottom of the hole, then the plastic pipe, then
>the concrete around the outside of the pipe. That lets any pooled water
>dissipate out the bottom of the plastic pipe. If you go to Google Maps, put
>
>35.348172,-84.307656
How deep were the holes?
--
PeteCresswell
Larry
x...@y.Invalid says...
> It sounds like, with the right kind of wood
("treated"... the
> greenish stuff?) that rot from pooled water is not a problem.
There is treated wood and there is treated wood. Some is
intended for deck joists, and just has termite
treatment. If you use wood, the kind you want is ground
contact rated.
Your idea of using steel posts is good, but steel will
rust. Hot dipped galvanized is the best, but you can get
reasonable protection from cold galv. Set steel in
concrete and do the drill and rebar routine. You have to
anchor it firmly to the concrete.
Futility Man
>How deep were the holes?
About 18-24 inches in mostly red clay. There were some fist-size rocks that
came out with the auger but not many. Water pooling around the posts has not
been a problem and the 4x4s are ground contact rated.
These signs have withstood wind gusts of 60mph for brief periods and sustained
winds of 35mph. Having the signboards mounted so they can swing has kept them
from being uprooted, I think.
In the same amount of time that I've not had to replace these sign posts, I've
replaced no fewer than five flagpoles that snapped off at ground level. They
were all thin wall aluminum. The pole I have now is a 20' stick of 1 1/4" moly
steel pipe covered in 1 1/2" white PVC drain pipe with a cap on top. I drilled
a 18" hole, dropped a shovel of gravel in it, stood a piece of 2" galvanized
pipe in it, and filled it in with quickcrete. If that ever fails, I'm giving up
on having a flagpole. ;-)