Max height for retaining with concrete gravel boards?

[Ivor Windybottom]

Is there a generally accepted maximum that can be retained with concrete gravel boards and posts?

A family member has a wooden fence, which was at the bottom of a slope. The previous owner stacked a load of rubble against it and built a patio on top. It's about 2 feet above the pavement on the left, rising to 3 feet on the right.

If it was mine I'd get a retaining wall built with fence panels on top. It's about 15 feet in all, so it wouldn't be very expensive. But budget is very tight, so I'm wondering if concrete gravel boards could work?

I'm thinking 9' posts, 2' into the ground. 3 stacked gravel boards with a 4' fence panel on top, as shown...

I absolutely accept that this wouldn't be pretty, I'd much prefer a wall with raised pillars and wood panels. But this would cost less, mainly as it would be done by this idiot instead of paying someone with actual skills. The stacked rubble is reasonably solid. I'd clear away what's fallen against the old fence, build the new one then pour 20mm gravel down the back of it.

The posts would be initially set in postmix, then I'd top up the holes with mixed concrete using 10mm ballast and sculpt it into a new surface beneath between the posts, boards and pavement edging. So the posts and boards would be very well held up.

The gate is for very occasional use. The house is terraced so the only other access is through the house, so it's useful to have for maintenance, not for everyday use. It's currently 3 feet up on the right, I'm moving it to the left where it's only 2 feet up.

But... is this beyond the strength of concrete posts and gravel boards?

 

[Harry Bloomfield]

Gravel boards, are quite thin, and will shatter under very little sideways pressure, they are only designed to take a vertical load, that of a fence panel above. The only way to make them more able to support a sideways thrust, is by providing them with additional, intermediate support at the back.

 

[Ivor Windybottom]

I think I almost persuaded myself it was a terrible idea while drawing it!

It would also look rubbish from the back street. I think it needs doing properly with a wall, this would be a botch.

I'm just attempting to come up with an answer for someone who really can't afford to do it properly.

 

[Old Salt]

That wooden fence appears to have retained it fairly well until it rotted out. I think I would be inclined to give it a go depending on the amount of rubble being retained.