replacing fence.... using it as a retaining wall

Originally Posted by havabeer

but its the back filling against the posts and rusting out that is the concern. I suppose as long as the posts aren't scratched or the paint damaged during install and backfilling rusting out shouldn't be too big of an issue same with having an some geo fab and ag line against it.

600MM isnt a small retaining wall.
There is no way I'd be using the colorbond fence posts for any type of retaining wall. Despite the surface color, they will still rust out...just like the fences when people build up garden bed against them. I'd be going down the path of what Cyclic posted...providing you install it correctly then zero issues in the future.


Your posts/holes need to be as deep as they are high as a minimum....dependent on the soil which can dictate a deeper hole. Don't forget there are additional stresses with the high fence/wind.
Holes should be min 350mm diameter, filled with concrete, slotted pipe with min 200mm of scoria encased in geo textile and inspection points at each end of the slotted pipe and if a long run, 1 in the middle (t join to a riser). Use agi drain but my preference is 90mm slotted pipe.

Another similar method. Uses concrete posts however. Bit heavier to install but won't ever rust out.
I certainly would not be relying on fence posts to retain 600mm, and I doubt you will be able to get any engineering cert to cover the install on a boundary.

Originally Posted by havabeer

Aren't most colour bond fence posts in 500 - 600mm deep? which is the height I'd be looking to retain? (yes you would then have the windage on the fence above it) its part of the reason I thought a lot of plinth companies recommend only going 600mm high max.

my original plan was to do something similar to cylics above but as its 13m away from the nearest structure I just figured holding back 350mm of dirt and 50mm of grass was going to bare it no ill will. seem to be no shortage of companies willing to do it, this one will give you a 600mm retain as long as you put a timber post in front:
https://simplyfencing.com.au/service/retaining-walls/

Hmmm, I would look seriously at that idea as it looks to me that the retaining wall has been built then the fence posts bolted to the wall.
Difficult to tell but I can see hex heads through the metal post extension and I very much doubt they would be bolts through a join in the wall

I don't see a colorbond fence post lasting very long as a retainer due to the light gauge of the material (rust) let alone weakness of the metal post
not only that but the stock posts are usually only long enough to go into the ground and take the fence panels
i.e height of fence + 450 for memory, so not enough to add a 350-450 retaining wall.

Do it once-do it right.A fence is not too bad to replace down the track
Replacing a fence+retaining wall is another ball game all together.

Talk to Stratco about your idea and get their advice.

I think the key bit is this

They can be installed up to 600mm high if posts are incorporated in front of them

Looks to me the timber posts are doing the retaining of the wall, the fence posts just align and join the ends of the sleepers and in doing so support the fence above.