Clay soil, digging it out

Hi, I have spent ages looking up what to do with my problem but can not find a solution for various reasons. I recently laid turf and didn't compact it so lifted it all up again. By doing this I noticed a lot of water being held. In this one problem area I have clay soil which is causing me problems with drainage. Before I lay the turf I intend to do the following: Dig out all the clay soil Drill large holes in the ground every 5 cm Add a 5cm layer of sharp sand Fill the rest with top soil Is that a good idea? How far should I dig down?


  • frensclanfrensclan Posts: 112

    Hi Gooner9; I sympathise, but at least it is in only one spot. When I moved to my latest house I found that the whole site was on a very thick layer of clay so that even the fields behind do not drain well. I tried digging sumps but they just filled with water and the land was such that I could not put in land drains as this would just have moved the problem to my neighbours. In the end I grow on raised beds and where the lawn is, put half down to a bog garden and pond and for the grass brought in a load of top soil and raised the level so that the water does not show sitting on top of the grass even though it is just below the surface. The lawn does not seem to mind this at all and has grown well.

  • Gooner9Gooner9 Posts: 8

    Seems like a lot of people have this problem!

    I can't raise mine at all otherwise this would be an option

    Would doing what I've listed solve it you think?
  • frensclanfrensclan Posts: 112

    Depends how deep the layer of clay is and how big the area. We dug out 3' down and were still finding clay . I was told it is meters thick here. Perhaps it would be worth digging a sample hole at the edge of the space and to see how deep your clay is. As I said we found that a sump simply  collected the water and overflowed onto the soil when full of rainwater. For us the solution would have been to put in land drains that fed the house drainage system but this was not technically possible.

    We did find spiking the area with a fork and filling these holes with sharp sand made a difference. I am sure there will be more advice coming your way from others on the site. Good luck with it.


  • GemmaJFGemmaJF Posts: 1,197

    It is sometimes better to re-plan the garden so the water runs away to a chosen point if the clay is very deep.

    I'm on clay also, I have it so my veg plot and area near the house both slope towards the wildlife garden which I accept will always be boggy and wet. Very similar situation to frenscian, we have a field out the back and it drains towards the garden, so the wildlife garden takes a lot of water from that also.

    You might get some improvement in the drainage by breaking it all up and adding grit and organic material to the problem area. It is usually worse if it is heavily compacted for some reason, so relieving the compaction may be all that is required. Though I don't regret taking the time to re-profile the soil in my garden to drain it away to where I want it, rather than having puddles outside the back door step!

  • Yes, Large grit and organic matter. Just not sand, if you mix sand and heavy clay and then get a bad drought, you run the risk of a garden full of cement. 

    If you can hold off until next spring, best long term solution might be to dig down as deep as you can, mix in plenty of manure/compost and large grit. Give it as good a digging over as you can and then leave it for the weather to get at. You could also plant a green manure crop over the summer, then dig it in over the winter. Once the winter frosts have had a go at the clay particles, they should be a bit better mixed up with the organic matter and easier to work with.

  • Gooner9Gooner9 Posts: 8

    I couldn't replan the garden, it's just off the patio so only grass can go there.

    So I ended up digging a lot of it out but not all. I went down to just below my knee and it still went on further. Hopefully what I have done will improve it at least.

    I couldn't hold off doing it as it was the final piece of the lawn to finish, I guess time will tell and I may have to readdress it at a later date.

    What do you guys mean by grit? as in scalpings?

    If anyone is interested I'll post back once it's finished as i ran out of time and motivation today digging it all out
  • LeadFarmerLeadFarmer Posts: 848

    Im on heavy clay also. In my front garden I recently had to dig a hole 4ft deep and it was still clay. I have nowhere to drain water to either. Any soakaways I've made have just held the water, and the problem returns. 

    Im relaying a new lawn this year and I shall first remove the old turf, rotate the compacted soil, add more top soil and sand, and rotate this into the existing soil. By rotating the area and raising the lawn a couple of inches I hope this will improve the situation.

  • Yes, thats exactly the grit I was thinking of. Makes a good slug barrier as well.

    Turn the old turf into the bottom of the hole you dig. Every little helps image

  • GemmaJFGemmaJF Posts: 1,197

    LeadFarmer it may well help, my veg plot drains pretty well, double dug to two spade depths and it is pure clay under that. Just be careful adding topsoil over clay. I did this with loam topsoil and it made it even worse. The water would sit in the clay making the loam like a complete mud pie on top. Most annoying as I spent ages leveling it all, but as soon as anyone walked on the loam it would leave huge squidgy boot marks. image So just be sure to check you really are getting the drainage you want before adding any topsoil. image

  • LeadFarmerLeadFarmer Posts: 848

    A good point, thanks GemmaJF

  • Gooner9Gooner9 Posts: 8
    What would you do if it doesn't drain? Digging 4 ft is a lot!

    Do you layer the grit and sand or mix it all?

    Thanks for the link to the grit
  • AtillaAtilla Posts: 1,493

    I would not amend the clay soil as it is just grass but if drainage is an issue (sitting water for more than ten minutes after heavy rain) then I would look at the lowest point in the lawn, cutting the turf up, remove all the clay and backfill with grit/rubble, cover the top 6 inches with compost and relay the turf. That should help as a quick and reliable fix.

  • Inpartially reseeded my lawn which is on heavy clay. I took some clay off it and topped with screened topsoil. However, the old lawn seems to be on a bed of sandy loam and red granite stones (like the decorative ones you can buy). It drains really well but grows well too. Not orthodox but seems to work. Grit seems to be the way to go to help break the soil up.

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