Post Foundations

aFlabbyPanda

After being very proud of building my own fence the bad weather at the weekend brought some of it down. Looking now its clear the foundation wasn't deep enough.

I'm guessing that I can't reuse the uprooted post anchors (with the set concrete attached) and instead dig the hole to probably twice the depth and use a fresh one instead?

karlitob

aFlabbyPanda wrote: »

After being very proud of building my own fence the bad weather at the weekend brought some of it down. Looking now its clear the foundation wasn't deep enough.

I'm guessing that I can't reuse the uprooted post anchors (with the set concrete attached) and instead dig the hole to probably twice the depth and use a fresh one instead?

As I understand it, it’s not the concrete per se that provides support but the depth of the hole. It’s the ground that provides the stability to whatever is above it.
If I remember correctly for a 6ft post, 2 ft needs to be underground. But that’s for concrete/wooden fence posts, I’m not sure about post anchors. I didn’t go with them as they feel as secure to me. I went mad and put in a metre deep hole. Glutton for punishment.

I would imagine that you would need a much bigger hole of concrete and then secure the anchors to that piece of concrete with sufficiently sized bolts that can take the weight of the wind blowing against that fence.

Can you put up other pics.

glaswegian

1 cubic foot hole should be sufficient, imo no need for anchor, insert post, fill hole with concrete, plumb post and repeat.

aFlabbyPanda

I should have explained the reason for the anchors here was to make this section removable, it's the side access to the garden.

awec

karlitob wrote: »

As I understand it, it’s not the concrete per se that provides support but the depth of the hole. It’s the ground that provides the stability to whatever is above it.
If I remember correctly for a 6ft post, 2 ft needs to be underground. But that’s for concrete/wooden fence posts, I’m not sure about post anchors. I didn’t go with them as they feel as secure to me. I went mad and put in a metre deep hole. Glutton for punishment.

I would imagine that you would need a much bigger hole of concrete and then secure the anchors to that piece of concrete with sufficiently sized bolts that can take the weight of the wind blowing against that fence.

Can you put up other pics.

What did you use to dig that out?!

Calahonda52

awec wrote: »

What did you use to dig that out?!

This will get you started, depending on the soil.
https://www.adverts.ie/hand-tools/bulldog-insulated-post-hole-digger/23369517

Markcheese

If you give the concrete on the anchors a few whallops with a sledge you'll see wether you can reuse them -

karlitob

awec wrote: »

What did you use to dig that out?!

By the end, both figuratively and literally, my fingertips!!!

https://hortipower.co.uk/en/earth-augers/37-82cc-post-hole-digger-auger-petrol-3-drills-bits-earth-borer-ultra-sharp-blades.html

Some places easy, some hard. I went with this yoke cos it had a 300 mm auger bit. As I got down further - I went narrower (200mm and 100mm) and used by trusty trenching shovel to open up the hole to that diameter.

Calahonda52

karlitob wrote: »

By the end, both figuratively and literally, my fingertips!!!

https://hortipower.co.uk/en/earth-augers/37-82cc-post-hole-digger-auger-petrol-3-drills-bits-earth-borer-ultra-sharp-blades.html

Some places easy, some hard. I went with this yoke cos it had a 300 mm auger bit. As I got down further - I went narrower (200mm and 100mm) and used by trusty trenching shovel to open up the hole to that diameter.

They are quite a dangerous weapon, if the auger gets stuck, arms get broken

chooseusername

aFlabbyPanda wrote: »

After being very proud of building my own fence the bad weather at the weekend brought some of it down. Looking now its clear the foundation wasn't deep enough.

I'm guessing that I can't reuse the uprooted post anchors (with the set concrete attached) and instead dig the hole to probably twice the depth and use a fresh one instead?

Why not use the spiked anchors ?

https://www.screwfix.com/p/sabrefix-fence-post-spike-75-x-75mm-2-pack/50094#product_additional_details_container

I think you can get a hard plastic block to stop the sledge damaging the bracket
as you hammer it in.
No holes to dig, no concrete, no spoil to get rid of.

jmBuildExt

glaswegian wrote: »

1 cubic foot hole should be sufficient, imo no need for anchor, insert post, fill hole with concrete, plumb post and repeat.

How do you know... OP didn't say how tall the fence was.

OP - how tall was the fence?
For me, the 1/3 rule (hole depth = ~1/3 height of the post) applies whether using an anchor or not.
The turning force of a 1.5m fence being blown by a gale isn't going to be affected by whether you have a piece of metal on the bottom of it or not.

kadman

/\/\/\
Ditto

Lumen

To counter leverage you need either a deep hole or a wide, strong slab.

Discodog

Dig just over 2ft deep holes. Cut 2 foot lengths of suitable pipe - like Wavin drainage pipe, so that it fits the post. Put a bit of gravel in the bottom of the hole for drainage. Concrete the pipe & the post will slide in or out when required.

Fine Cheers

https://www.youtube.com/watch?v=wIRn-MqFYwo

aFlabbyPanda

Fine Cheers wrote: »

https://www.youtube.com/watch?v=wIRn-MqFYwo

That's what I followed to build the fence actually, only changing this section to use the clamps to make it removable. This section is 1.8m high and about 2.4m wide.

I don't want to dismantle the fence so using new posts is out. I'm going to try the spike clamps and refill the hole with concrete again. The ones at my local hardware have a depth of 45" so about twice what I had before.

If needs be I can always add a diagonal brace on the rear side. I'll let ye know how I get on. thanks all for the replies.

standardg60

aFlabbyPanda wrote: »

That's what I followed to build the fence actually, only changing this section to use the clamps to make it removable. This section is 1.8m high and about 2.4m wide.

I don't want to dismantle the fence so using new posts is out. I'm going to try the spike clamps and refill the hole with concrete again. The ones at my local hardware have a depth of 45" so about twice what I had before.

If needs be I can always add a diagonal brace on the rear side. I'll let ye know how I get on. thanks all for the replies.

Knock the existing concrete off the supports as suggested, dig the holes twice as deep and reset in new concrete. It wasn't the depth of the clamps it was the depth of the hole.
Unfortunately i don't see how you can do this without dismantling the fence from the posts and reattaching when the posts are set.

Discodog

aFlabbyPanda wrote: »

That's what I followed to build the fence actually, only changing this section to use the clamps to make it removable. This section is 1.8m high and about 2.4m wide.

I don't want to dismantle the fence so using new posts is out. I'm going to try the spike clamps and refill the hole with concrete again. The ones at my local hardware have a depth of 45" so about twice what I had before.

If needs be I can always add a diagonal brace on the rear side. I'll let ye know how I get on. thanks all for the replies.

Most clamps only hold 6 inches of post which isn't enough for a 6 ft fence.

aFlabbyPanda

But the posts didn't come away from the clamps, the clamps (and concrete) came away. Surely if the clamps had deeper foundation via a deeper hole, that should prevent this happening again right?

Setting the posts into concrete isn't a solution for me where this fence is going.

karlitob

aFlabbyPanda wrote: »

But the posts didn't come away from the clamps, the clamps (and concrete) came away. Surely if the clamps had deeper foundation via a deeper hole, that should prevent this happening again right?

Setting the posts into concrete isn't a solution for me where this fence is going.

Can you post some other pics to get a better idea.

Ultimately, you can either set them right or continue having them fall down.

If the concrete is under ground, I’m at a loss to see why you can’t use it, unless something is below the ground that you can’t move.

Surely a deep concrete footing, with the post holders secured to the concrete footings would be a reasonable approach.

Lumen

aFlabbyPanda wrote: »

But the posts didn't come away from the clamps, the clamps (and concrete) came away. Surely if the clamps had deeper foundation via a deeper hole, that should prevent this happening again right?

Setting the posts into concrete isn't a solution for me where this fence is going.

The weakest link gave way. If you reinforce the connection between post holder and ground, it's theoretically possible that either the post holder or the post could fail next, but I don't see it myself. The post will eventually fail, probably at the connection with the post holder, but that's how all fences fail, because it's the point of maximum leverage.

Discodog

If you put a 6ft post into a 6 inch holder the leverage is huge as the edge of the holder acts as a fulcrum.

aFlabbyPanda

So I finally got around to this yesterday. I went with the 30" spike post anchors and refilled the hole with postcrete.





Seems to be stable enough and much more so than the small holes I'd dug, on to the next project.

Fine Cheers

Good stuff. How many uprights between gate and hedge ?

aFlabbyPanda

Fine Cheers wrote: »

Good stuff. How many uprights between gate and hedge ?

3 uprights,