Trouble digging fence post holes...

[imanc]

Hi,

I'm trying to erect a fence over the site of my house's previous back yard wall.

it's a victorian terrace and most of the walls on the row have been removed so people can park their cars in their back gardens. However due to having dogs and no car, I need a fence.

The fence is being erected between two brick walls (about 11ft distance), and I've already fixed two 3" thick fence posts to the brick walls at either side. Now I need to insert two fence posts into the ground which will be ~ 4.5 feet apart.

Two issues:

1) Getting through the brick foundation is proving extremely challenging using a cold chisel and standard hammer drill. I've managed to remove two bricks from one of the holes, and have produced a ~7inch hole. I'm trying to get at least an 18" hole, so the posts can be rock solid.

2) Gas, electric, cable lines come in at the front of the house, but there's still sewars and water lines probably entering at the back (water meter is in back yard outhouse and there's a man hole in the back yard). I'm wary of hitting anything. How can I find out where these services reside and how deep they are?

There's going to be 4 fence posts and two of those are firmly affixed to the brick walls at either side, so only two posts need to be stuck into the ground. I'm planning to use arris rails and vertical feather edge boards, and I'm wondering if fence posts postcreted into shallow 8" holes could be strong enough given the posts are close together and close to wall anchored posts. Or is this asking for trouble?

Cheers, imanc

[The Natural Philosopher]

If the foundations go deep enough than concreting the posts to those somehow will be good.

Or hire a digger and tear the foundations up, and then use the trench left to set the posts in.

if you go carefully and trench down one side first you should see if you are about to rip up cables or pipes.

sledge hammer is better than cold chisel BTW. smash them stuff up and pick it out with a pick. If you want to do it the hard way .

[harry]

Go down to the tool hire place and hire a breaker for half a day. Just make sure you don't hit any services. Or get yourself a long crowbar to prise bricks out. Something four or five feet long.

[Muddymike]

I doubt there will be any services to worry about in the foundation of the old wall. You do need to go down more than 8", why not hire a Kango for half a day?

Mike

[Nightjar]

If there is car access, there is access for a small digger, which will be a lot less work.

Open the manhole and look which way the drains run. You could also ask the utilities if their maps show where they enter the property.

Fence posts should be 1/3 underground and 2/3 above ground, so 8" would be OK for a 16" high fence. If you want the fence to last, use concrete posts and concrete gravel boards.

Personally, I would use the existing foundations as the base for a new wall.

Colin Bignell

[Alan Braggins]

If it's bonded into the old foundation, I would have thought an 8" hole was adequate to use a concreted in or bolt down Metpost, even if it's not the neatest solution.

[Andy Champ]

Doesn't this rather depend on the nature of the ground?

We're on sand here (OK, very sandy soil) and 1/4 underground appears to be fine. All the failures I have seen have been post rot, not uprooting.

Andy

[Another John]

You can get a heavy, long, steel chisel type affair -- I *think* that this is what I mean:

/

John

[Nightjar]

It is a good rule of thumb, which also assumes that the post is properly secured for the soil conditions. You can get away with less, but you are then betting we won't get another Great Storm.

Colin Bignell

[RobertL]

If the bricks are so well fixed down why not bolt the posts to the brick using brackets?

Robert

[SteveW]

Just use slot in post and cheap fence panels - any high wind will blow out the panels without moving the posts at all ;)

SteveW

[ss]

brackets?

Instead of working on a theory (not being funny) set one post as you have it (a couple of layer of brick removed) let it set for a couple of weeks and knock F... out of it with a sledge hammer and see what happens. That would give a good indication if its likely to stay put in a storm or keel over. Otherwise keep digging or take a chance. :-)

[imanc]

WHen you say "use the existing foundation", what does that mean? Does it mean I can dig a shallower than normal hole, fill to concrete or postcrete safe in the knowledge that the concrete will bind the post and itself to the already rock solid foundation? Or do you mean something else?

I'm leaning towards hiring a breaker tomorrow and finishing off these holes.

I've had trouble trying to lift the drain cover, which looks like it hasnt' been lifted in about 100 years. But it is inline with a large stone that was obviously laid across the previous gate. I'm hoping the drain exits the property in a straight line, which means it'll go under this stone, which means I'm clear.

I plan to work it slowly, brick by brick, with the breaker and see how it fairs.

Though that long wrecking bar from wickes looks interesting.. hmm

[Nightjar]

Whacking the posts with a sledgehammer will show if they are going to fail, but I rather doubt it would replicate the loads the wind can exert.

Assuming the fence is 6ft tall and given the description of four posts (i.e three sections) at 4'6" spacing, a fairly modest 60mph wind would give a wind load on it of around 3/4 of a ton. To survive the 120mph (or possibly more - the anemometer at Shoreham by Sea failed at that point) gusts experienced in SE England during the Great Storm, it would need to withstand around 2.7 tons wind loading.

Colin Bignell