Another drainage/clay question sorry!

[andystephens]

Hi all

I was hoping someone might be able to advise on drainage solutions for our garden. Bear with me while I try and describe the situation…!

Our garden is approx 35’ x 35’ and slopes away from the house. It’s very heavy clay underneath the upper half of the garden (a few inches under the lawn in places), but the clay layer seems to drop away towards the back of the garden (perhaps a foot or so below ground level at the far end). The garden has been landscaped into 3 tiers: the top tier nearest the house is around 7ft front to back, paved and with a low decorative brick wall dividing it from the middle tier. The middle tier is lawned (this is where the drainage problem is), and approx 15ft front to back. The lawn is approx 16 inches below the top tier. The third tier is around 10 inches lower than the lawn, and a railway sleeper wall separates these two tiers. The wall is two sleepers high with the top flush with the lawn. The lower sleeper row is half buried in the ground. There are no drainage holes anywhere in the sleeper wall as I thought the gaps between the sleepers would be adequate.

The garden is level from one side to the other, however the garden of the neighbouring house on one side is a couple of feet higher than ours, and the garden on the other side is a couple of foot lower, due to the estate being on a hill.

If you are still with me, here's the problem: our lawn area gets very soft and muddy even after a little wet weather, and it only takes a few footsteps in the same area to wreck the grass. Some patches of grass (especially close to the brick wall) are very sparse, and there are a few small spots where you can almost feel yourself sinking (perhaps a slight exaggeration). We have one of those lawn treatment companies visit us, and they suggested digging a narrow gravel-filled channel along the bottom of the brick wall and down either side of the lawn, but I’m not convinced that this would help much, although it might help divert any rainwater that flows from the patio level down the steps onto the lawn. The lawn has a very slight slope (perhaps 4 or 5 inches from the brick wall to the sleeper wall) which I assumed would be enough to clear any surface water during rainfall? I’m not sure if rainfall is really the root cause, or simply down to all the underlying clay around here.

Other than digging out the entire lawn to a decent depth and replacing the clay with top soil, I’m not sure what else I can do. Any suggestions would be much appreciated, plus comments on whether this drainage channel would be worth the effort or not.

Thanks in advance
Andy

[lutonlagerlout]

bear in mind andy we had the wettest November on record,followed by untold snow
My allotment is under 50mm of water right now yet in the autumn it was dry as a bone
trenches with gravel sound like a fail to me
if you are going to do it i would install a land drain buried in shingle and wrapped in a non woven fabric terram ,multitrack etc. work for this
here is a link for more info on land drains
cheers LLL
btw might be worth trying to drill some weep holes through the sleepers first

[Tony McC]

Your only viable drainage option is onto that third tier: what would happen to the water dumped on there?

Assuming there was some way of removing water from that third tier, and also give that the current lawn on tier two is shagged, I'd look at digging out the lawn to around 300mm, laying a waffle board or aquadyne or similar, backfilling with a VERY sandy loam, and then re-turf in mid-spring.

The key point to bear in mind is just where will all the drained water go to.