Clay soil under lawn

1 May 2006
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United Kingdom
While I await for autumn to scarify and aerate my lawn I’ve looked into what’s underneath a bit.

I had to concrete in the washing line post holder, as it was a hot day and being lazy I poured water before digging, then dug a bit and added more water, the water just sat in the hole and didn’t drain, so I’m assuming the soil under the lawn is clay and is the reason the grass doesn’t really grow.

So I’m wondering what I can do, I’m thinking something like this but looking for advice

Top dress (with lawn seed)

I’ve also seen Aerify plus which is supposed to break down the clay, the professionals must come across this a lot so thought I’d ask the question

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How deep is the topsoil above the bed of clay?

I’m not sure to be honest, this was a new build house in the 80’s so I’m wondering if it was just a thin covering and then turf but I’d need to get my spade out to check - can’t really do for a few days

Unless you're willing/able to break up the clay and introduce top soil/sand to aid drainage your best bet is to accept what you've got and build up the grass as you suggest.

I've not come across Aerify plus but doubt it would make any real difference in your situation.

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My lawn is thick with clay underneath (can almost re-create the scene from Ghost with the amount under there). Looked a sorry state when we moved in.

Answer for me is to use a hollow tine aerator once or twice a year. Water it well with a sprinkler and keep off the lawn for a few days afterwards. Don't try to fill the holes with sand or soil -- that only works on a completely flat, closely-cut lawn.
Well I dug a small hole, it seems to be heavily compacted soil (couple of pics attached) I only went down 100mm as assumed that should be enough however it was pretty solid.

So I bought an electric scarifyer / aerator as I previously did it manually with a rake and fork but it took a lot of effort, maybe this isn’t my best option?


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you never know what the builders did before they hid it under turf. Probably stacked bricks and drove backhoes around on it. Then buried scrap and rubble and leaked diesel and readimix on it.

If you have borders, you can dome it slightly or add a slope so that any excess drains into the beds, which you can dig and loosen as deep as you want.

Breaking up a hard pan is done by farmers with a sort of subsoil plough. Beyond DIY scope. if you happen to like roses or potatoes, plant some in beds and move the bed along a bit each year until you have double-dug the whole thing.

You can top-dress a lawn with grit but it will not help your deep pan.
Some good points there - stacking bricks etc....

Would aerating help at all or am I wasting my time


As John said.

My previous house was an early seventies build, and the back garden lawn was either concrete, or a bog. Probably due to the machines on site at the original estate build just crushing whatever was there flat.

Depending on how fit, enthusiastic, and mad you are, you could do what I did ; dig the lot out (to a couple of feet deep, in my case), skip it, put drainage in, then put fresh top soil and grass down. Ended up looking mint. And then, we moved......

Didn't take long, but then the garden wasn't big, and I was fifteen years younger.....

Would love to do the same now, but I'd almost certainly be digging my own grave!
I’m wondering how much it would cost to get a guy in as I can’t be arsed to dig it all up, then you have to consider if it’s worth it or not....

Planning on doing the garden patio at some point so maybe do the whole thing, I can’t work out how it’s compacted so much to be honest, the people before us changed the landscape (badly obviously) rather than a sloped lawn they split it into 2 levels

They could (possibly did) have dug all the clay soil from the lower part and used it to build the higher level but will never know


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