My border partition using concrete flags

[DIYalot]

Hi. I'm using concrete flags/pavements, that are 900mm x 600mm x 50mm as a border between my garden and next doors. I'm laying the flags vertically, along the 900mm long side - so the flags stand in the vertical 600mm.

There is difference of height in the land between my garden and next doors, which is 11cm.

Here are the details of the cross section: The flags will be set into the ground 29.5cm on the neighbour's side. On my side, the flags will be set into the ground 40.5cm. This means that there is 11cm more in terms of depth of soil on my side. Of course, that means we don't have a balanced situation in terms of forces - there will be more force acting on the flag on my side than the neighbours side. due to the extra 11cm of soil on my side.

Now, I am intending to just fill in with the soil and tamper the soil down as it's put in The question is, if I simply fill in with soil, will the flags have a tendency to lean over in time, because of the difference in the ground levels on either side of the flags?

Also, I have a pile of sandstones that I've dug up from the garden - would it be better if I filled in with these stones and tampered them down?

Do I really need to set the flags in concrete? Thank you.

 

[DIYalot]

When you look at the situation, it's like putting in a flag nearly 1 foot into the ground, then laying up a layer of soil on one side about 4.5" deep. Perhaps some would figure that ain't going to lead to the flag leaning over. Even if it's just back-filled with the soil.

 

[Halitosis]

Might be fine for a period, but in time they'll start to lean. How soon that is depends on the soil, how well you tamped it, drainage, and load on the upper side (pathway?). If you're going to the trouble of digging out to put the slabs in the ground, why wouldn't you set them in concrete rather than soil? Doesn't even have to be both sides of the slab (though that would be best). All you need is a shovel, something to mix it in/on, and a bit of effort - done properly it will last a lifetime and you only need 6 inches of concrete which can be covered over with soil or whatever for another 6 inches.

 

[DIYalot]

I attach a drawing of what I'm thinking of doing. Basically making a 150mm wide border next to the flags on the side the flags will tend to want to lean.

 

[Halitosis]

It would be more stable if the concrete is at the bottom of the slab, and you can then also cover the concrete with soil giving a clean finish and more planting space

 

[DIYalot]

Here is my latest design. The fencing is to sit above the boundary partition, which, at it's least embedded, is embedded 300mm into the soil. The idea is to use repair spurs (Godfathers) to attach a fence to. In my first draft, I've drawn an arrangement using spurs 1000mm long. And there is a concrete "step" attached at the bottom of the spur that results in a cantilver to prevent the partition from slowly keeling over with time (actually there is about 100mm depth more soil height on the side of the step, and there will be flags laid on that side for a section). I think the design in OK. My only real concern is, is the spur embedded deep enough. Should I be using a longer spur? I mean, it's only embedded 300mm and it's entire length is 1000mm. Maybe that's fine, I dunno.Thanks.

 

[DIYalot]

Looking at some data from Supreme Concrete, a hole needs to be about 2 foot deep. So, any stud needs to be at least 600mm in the ground and at least 1300m long. I think therefore we'll be talking a post 1.35 - 1.4m long to do the job. I think that's about right for this job.