Lawn, deep in the clay?

[Tony K]

Afternoon all.

 

I know this is probably more a gardening question than anything else, but this forum almost never fails to come up trumps, so here goes....

 

In order to achieve acceptable building heights or my SB I have had to reduce the site level by up to 70cm, removing all topsoil and exposing thick, heavy clay in the process.

As the site is excavated it acts as a bit of a sump to neighbouring land. I have a large underground tank and pump system to remove rainwater into the local sewer system (all signed off by the water board etc).

 

I will have a small garden, with space for a lawn of about 25m2 (5m x 5m). I had resigned myself to fake grass, but have come to wonder whether I could in fact grow a decent lawn.

 

Working from the top down, my idea is to create the following arrangement:

 

1. A lawn grown from tough grass seed (i.e one that can withstand kids playing) or suitable turf rolls.

2. About 8 inches of topsoil, mixed in with some gravel perhaps.

3. Some sort of spiking of the clay bed (don't know exactly why or how!).

4. A French drainage system (100mm pipe, perforated, wrapped in geotextile membrane and set in shingle) leading into the rainwater / sewer system.

Am I on the right track? I don't know what sort of seed or turf to go for, or if there are some important tricks and techniques I should use. The drainage seems like the right thing to do, but I've no idea if it will work.

 

The lawn should get decent sunlight, and though I intend to plant a few medium size fruit trees around the edge of the garden, these will be in raised planters rather than in the lawn itself.

 

My big fear is that I will end up with a boggy mess in winter and a solid wasteland in summer!

 

Thanks

[SteamyTea]

I don't know much about grass, except it grows on poor soil quite well.

If the area is not too large, and you are considering a French drain around the edge, why not also put in land drains, they are only pipes with holes on them, surrounded by stones.

I really don't know what I am talking about, but fields around here have them as we get a lot of rain.

[Tony K]

28 minutes ago, SteamyTea said:

I don't know much about grass, except it grows on poor soil quite well.

If the area is not too large, and you are considering a French drain around the edge, why not also put in land drains, they are only pipes with holes on them, surrounded by stones.

I really don't know what I am talking about, but fields around here have them as we get a lot of rain.

 

My definition of a French drain (probably incorrectly) is more or less what you have described to be a land drain!

Either way, the land will be drained!

[SteamyTea]

https://en.wikipedia.org/wiki/French_drain

 

Seems like a good solution.

[markc]

Yes French drain and land drain are pretty much the same thing. Spiking wouldn’t achieve much unless the clay is a layer you can punch through and fill the holes with pebbles/hardcore etc.

either real or fake grass your main task is to move (allow it to move) the water away to prevent pooling.

[Tony K]

14 minutes ago, markc said:

Yes French drain and land drain are pretty much the same thing. Spiking wouldn’t achieve much unless the clay is a layer you can punch through and fill the holes with pebbles/hardcore etc.

either real or fake grass your main task is to move (allow it to move) the water away to prevent pooling.

 

Cheers @markc. I will drain it well and give it a go. If all else fails I will pave the bloody lot of it!

[ProDave]

1 hour ago, Tony K said:

In order to achieve acceptable building heights or my SB I have had to reduce the site level by up to 70cm, removing all topsoil and exposing thick, heavy clay in the process.

This is where it started to go wrong.  I hope you did not get rid of all that top soil as "muck away"?

 

I would have removed a lot of that clay as "muck away" and put back a good thick layer of your top soil on the bit that is to remain as garden.

[Tony K]

3 minutes ago, ProDave said:

This is where it started to go wrong.  I hope you did not get rid of all that top soil as "muck away"?

 

I would have removed a lot of that clay as "muck away" and put back a good thick layer of your top soil on the bit that is to remain as garden.

 

I have two or three jumbo bags of the old topsoil sitting there waiting to be used, and several more loads of it already spread across the lawn of the house we live in at the moment!

[joe90]

I built on solid clay and have similar problems. I was recommended a French drain rather than a land drain (trench filled with stone rather than perforated pipe). The perforated pipe, especially with a membrane wrap tends to get blocked easily with clay particles. We have a French drain around the house piped out to a road ditch and it works well. If yours is the lowest land around you will have to pump it out, just connect the French drains to the pump station. 4” of decent topsoil should be fine fir grass 👍

[ProDave]

4 minutes ago, Tony K said:

 

I have two or three jumbo bags of the old topsoil sitting there waiting to be used, and several more loads of it already spread across the lawn of the house we live in at the moment!

Good, so dig some trenches across the clay filled with stone and perforated drain pipe leading to a perimeter French drain and put all your good soil on top and sow some grass.

[Mr Punter]

I did a development and the ground was clay.  Did a French drain to an old well and pumped to a ditch at the top of the drive.

[TonyT]

Add sand into the top soil mix to allow for aeration and drainage.

50/50 mix.

[gc100]

Grass grows fine in clay, you just want to avoid standing water really. It retains water longer so has advantages as well. 
 

My whole garden is clay based (~1500m2). I seeded it at the beginning of Sept and it’s doing great so far. 
 

french drains (with stones) and 4” top soil you’ll be totally fine imo 

[Tony K]

16 minutes ago, ProDave said:

Good, so dig some trenches across the clay filled with stone and perforated drain pipe leading to a perimeter French drain and put all your good soil on top and sow some grass.

 

Ta. That sounds suspiciously like the plan outlined in my original post!

[Tony K]

1 minute ago, TonyT said:

Add sand into the top soil mix to allow for aeration and drainage.

50/50 mix.

 

Is there a method for mixing the two, or is it just done roughly shovel at a time as you go?

[TonyT]

Whatever works for you, mini digger mixing it, filling gorilla tubs by hand  and tipping out, your shout.

[gc100]

Worth a read https://www.gardeningknowhow.com/lawn-care/lgen/using-sand-on-lawns.htm