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What use to level garden?

Hi all,

We're hoping to create 2 tiers in our currently sloping heavy clay garden. We've had conflicting advice on what to use and there is already poor drainage so I don't want to make that any worse!

There is a 60cm drop over about 7m that we want to level. Should we ideally use all topsoil to do this? A landscape contractor said using anything other than topsoil would cause drainage issues. However our neighbour farmer (who I presume is more familiar with our heavy clay soil) said using all topsoil would cause drainage issues.

Would really appreciate any advice! 
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Posts

  • K67K67 Leicestershire Posts: 2,507
    Can you post a few photos please.
    If you are taking one portrait crop it slightly before loading otherwise it loads sideways.
    Photos taken landscape seem to load fine.
  • LoxleyLoxley NottinghamPosts: 4,976
    edited April 2021
    Fill in immediately behind the walls with free draining fill material like clean crushed limestone or angular gravel with no fines, and connect into this with weepholes through the walls. 

    I would have thought infilling with a reasonably free draining topsoil to create level planting areas behind would be fine.
  • K67 said:
    Can you post a few photos please.
    If you are taking one portrait crop it slightly before loading otherwise it loads sideways.
    Photos taken landscape seem to load fine.
    So the purple is the infill area. The red line will be the retaining wall between the upper and lower tier. 
  • LoxleyLoxley NottinghamPosts: 4,976
    Are you digging down on the other side of the wall to lower levels and placing excavated soil in the purple area to create a flat space?
  • There isn't much soil on the other side of that red line. It's already relatively flat. Unfortunately we don't have much "donor" soil to take from the garden so we'll be buying the soil. We also have a builder who's going to bring us some soil for free. 
  • It doesn't look like much but it comes to 80 tons of material needed to fill in the purple area from the back fence to the red line!
  • KeenOnGreenKeenOnGreen Posts: 1,739
    We have an 8 foot drop over 7 metres, so your garden is almost flat to me.  Is there a reason that you want/need it to be perfectly flat?  To my eyes it's flat enough to use for gardening/socialising, etc.  Retaining walls, whatever they are made of, are time consuming and costly to install and maintain.  Have a think about whether you really need them.  They are also a faff when you want to wheelbarrow or carry something heavy from terrace to terrace, and have to negotiate stairs.

    We are on heavy clay.  We put several feet of pea gravel behind our retaining walls (made of railway sleepers), and a membrane between the soil and the retaining wall, to reduce rotting of the sleepers.  We have added some top soil on top of the clay.

    We did dig a couple of draining ditches, with porous drainage pipes surrounded by gravel, but only because we had a very steep garden.  With drainage holes put in your retaining wall about every 2 metres or so, you should be fine.
  • It's decieving in pictures! Although it's not steep it's really uneven and it's slopes in all different directions, towards the driveway and towards the fence. 
  • Did you use any subsoil levelling out the ground? 
  • KeenOnGreenKeenOnGreen Posts: 1,739
    We moved the existing soil from higher parts of the terrace to the lower areas (mostly clay), to make our terrace as flat as possible.  We didn't need to buy in any topsoil, as that gave us enough.

    Pure clay is not very nice to garden with, or to walk on when wet, so you may be best to bring in some top soil to put on top of the clay.  As long as you have sufficient drainage holes in the retaining wall, you should be OK.
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