Levelling my garden - potential can of worms?

[fex10]

We're on a hill and the two side of out 5.5 X 30 m garden have approx 0.5 m height difference. I'll do a full survey soon with a laser level because I don't know how much it slopes length ways.

We're about to dig a hole for a raft foundation for a prefab garage. We'll have the digger for a week so wondering if we should also level the garden and then patio it.

my worrys are:

1. Will it take time for the soil to settle and will we have to read adjust any dips after it settles? How long would we need to wait before we can patio it?

2. Do we need to treat the topsoil separately from the clay underneath? Ie should we remove the top soil and then level the garden?

I know we'll need to the fit gravel boards to hołd back the height difference on the boundary of our neighbours gardens.

 

[footprints]

Certainly need to seprate top soil dispose of the clay and then replace the good stuff. Concrete posts and gravel boards would be a good idea. Not too sure about a .5 metre bank to hold back though might be better with a low wall if it is more than a standard gravel board in hight.

Oh and yes I guess you you can store your worms in a large can with soil to put back later

 

[munchingB]

if you have 50cm difference between one side of the lawn and the other then you need to reduce the high side by 25cm and raise the low side by 25cm. no need for a wall : )

 

[fex10]

Yep, so I will take 25cm soil from one side and move it to the other side.

I've been told by a friend that I don't need to wait for the soil to settle, to use a compactor and put the slabs straight down.

So, I should remove the top soil, do the levelling and then replace the top soil?

 

[Andyc84]

If you are going to place a patio, why worry about the top soil?

you need to be careful if you are lowering and rasing sides by 25cm, will you undermine a fence or wall? has your neighbour got anything near the boundary that you could effect. a foot of soil can still cause damage to fences, it will also increase the rot in any wooden fence you place against and could easily topple the fence.

on the other hand you could slope the edges and remove the "placing soil against" issue.

 

[fex10]

If you are going to place a patio, why worry about the top soil?

That's what I'm looking for advice on Should I worry about it or should I not?

you need to be careful if you are lowering and rasing sides by 25cm, will you undermine a fence or wall? has your neighbour got anything near the boundary that you could effect.

The garden fence is being replaced as part of this job. But yes, good point, the neighbour has a pond that could be affected. But it is on the side that we are raising, so we won't undermine it.

 

[WalksWithTurkeys]

Be careful about anything under the ground. Sewage, and utility pipes should be deep, but they don't always follow the regs. I came across pipes from the gutters extending out into the garden about 8" deep, close to the house of course. And I also found two disused septic tanks at the end of the garden about 12" under, and 6 foot by 6 foot.

 

[r896neo]

You can not use clay fill to bring up an area to be paved unless you are willing to wait years.

You should really bring it up in a granular fill like MOT type 1 or 2 and compact it in layers as you go.

 

[fex10]

You can not use clay fill to bring up an area to be paved unless you are willing to wait years.

You should really bring it up in a granular fill like MOT type 1 or 2 and compact it in layers as you go.

This may be the answer I was looking for (but hoping not to hear

So does this mean that I need to remove soil on one side, dispose of it, and raise the other side using proper hardcore?

 

[r896neo]

Yes. Your friend who said to just compact the clay is a numpty.

You need to dig off at least 4 inches of grass and top soil then start adding sub-base.

How deep do you have to fill? That will determine what you use.

 

[fex10]

How deep do you have to fill? That will determine what you use.

I'll try to survey it tonight with a laser level. It's raining now and the laser level doesn't work outdoors during the day.

 

[fex10]

So the garden is 30m x 5.5m. It is fairly level length ways. Width ways there's a 0.34m difference. I need to think about what to do...

 

[fex10]

Ok, so I'm thinking that I can only part level the garden, just improve the situation.

1/ If I'm using sub base do I put that on top of the top soil, or do I remove the top soil first?

2/ What substrate? Is there anything cheaper that MOT1? Maybe just plain non clay soil?

3/ Do I then replace the top soil on top of the sub base?

4/ How thick should each layer be before I compact it?

5/ Do I pay to dispose of my top soil?

 

[r896neo]

sorry its not that clear what you want to do? why would you put top soil back unto the sub base?

To be clear, you can happily use sub soil to increase heights of a lawn or flower bed area. You should never use soil of any kind to raise an area which you then intend to pave within a few years.

You could use type 2 or 3 but you need a very heavy vibrating roller to compact it rather than a normal wacker plate.

A sub base should be installed on firm ground with at least some of the top soil removed. If it was lawn then 5 inches should suffice. if it was a flower bed then down to firm undisturbed ground, probably 8 inches.

 

[fex10]

sorry its not that clear what you want to do? why would you put top soil back unto the sub base?

Top soil just seems like fertile and valuable soil that should be kept. But ok, if the norm is to dispose of it then sure. We're paving the garden so it's of no use. I just fel;t guilty about getting rid of it.