Depth of concreted in posts

[Dunning]

I have a pair of concreted in posts that have been broken off at ground level and looking at the post way to replace them.

2 - 100 x 75 mm posts are used as the support post for a gate. I've spent some time drill/digging one out and have passed 200mm deep and wonder how much further down they will go. It's located in near the edge of the concrete slab and I don't want to have to cut it up if I can avoid it.

Any ideas about how deep the holes will end up being?

Any other ideas regarding replacing the posts?

Cheers.

[Don't believe the Hype]

Is the post holding a gate or just a fence? What height above ground is it?

[Dunning]

The post is holding a gate, 1800 mm above ground to the top of the post.

[Don't believe the Hype]

Lots of pressure on the post ordinarily you'd want at least 600mm - could you use a combination of concreting in the post and brackets dynabolted into the concrete?

[Bob Kane]

Any ideas about how deep the holes will end up being?

600mm .

[Tortoise]

I have just had to do this job on our fence after the April storm. Had to replace 8 posts with 600mm deep footings. Found the easiest way was to drill 2 holes into each footing, then put concrete bolts in (not dynabolts, they just pulled out). Then attached a chain and pulled it out with a farm jack (google image it). You can pick them up for about $150 on trademe. Worked a treat, 20 mins to get each footing out. Then you can insert new post in exactly the same place and re-pour the footings without having a massively widened hole.

[Perry]

Then attached a chain and pulled it out with a farm jack (google image it). You can pick them up for about $150 on trademe. Worked a treat, 20 mins to get each footing out. Then you can insert new post in exactly the same place and re-pour the footings without having a massively widened hole.

That's a clever idea.

I've always favoured timber posts because of the problems inherent in replacing broken concrete posts.

[sparxNZ]

Best way to remove a concreted fence post is with an impact drill with a chisel tip set to hammer only. cheap to hire if you don't own one. just put the tip on the concrete, pull the trigger and hold it there. concrete will split in half where the chisel contacts it after 30 seconds or so.
If you're hanging an aluminium gate a square 150x150 H5 wooden post will be fine. embed it in 60cm of concrete. If it's a heavier gate consider a steel post, a 2.4 meter length of steel box section from an engineer might cost you $60 and you can get him to drill and tap the hinges on at the same time. square wooden posts tend to bow and twist with heavy gates hanging on them. I learned that the hard, time consuming and expensive way. I use steel for everything I possibly can nowadays, once it's done it won't move for decades.