Depth of soil for new lawn

I dug an exploratory trench in the lawn to better understand the waterlogging. I have a very solid, very orange clay pan at two spade depth but it is dry down there. It seems the waterlogging is in the top four inches or so. Must I break up the clay pan as part of the preparation for sewing a new lawn?

 

I think it's quite normal to have clay at that depth. The fact that it's orange says that oxygen is making it down there, which means the soil above it is probably good. Incidentally, the orange colour comes from oxidised iron, aka rust. When oxygen doesn't get down that far, the clay would be grey and often stinky, but I digress...

When you say it is waterlogged in the top 4 inches, is this most of the time? Some of the time? Only when it's rained a lot?

 

Thanks for the information @clueless1. It's good to know that the orange is a good sign.
The wet area has been under water since we moved in last year. There were 4 reed type plants thriving in it, possibly Junkus, that I removed. Also a sea of marsh orchids that I plan on saving as soon as they appear.
Hubby thinks perhaps there is an underground spring so that's why I dug a deep trench. I suppose as the waterlogging is only at the top that is not the case. Perhaps water is running off from the neighbouring property .... A hardcore area used to park their cars and about 1.5 - 2 ft above us.
If the thinking is that this area will always be wet then I shall have to embrace that and have a bog area. I am not keen on this since we have leeches ... three found between yesterday and today.

 

The neighbouring property height in relation to us.

 

Does sound like run-off from next door.

I bet @Zigs knows how best to stop it. He's got loads of experience of flooding.

 

Thanks @clueless1

 

Do you mean the reeds and marsh orchids @Loofah? I'd never considered that the waterlogging was intentional. When I was digging out the bed at the fence below the neighbouring property I dug out a good number of thick plastic sheets just at the area that is waterlogged. I assumed they had been the cause and that things would dry up. Perhaps there's more beneath the lawn and I just dug the trench in the wrong bit......

 

I wonder why someone would have buried plastic sheets.

I wonder if it was a half baked attempt at creating a garden where there was once weed infestation. Perhaps plastic sheets were put down to smother weeds, and then someone just chucked some top soil on top of it? Intriguing. Sounds like a good case for a bit of diy garden archaeology.

 

Hahaha @clueless1, the previous owners of our last house laid grass above 60x90 slabs over a 60m x 10m area. It was a lot of fun sorting that mess out but we were young then.
Think I'll widen the trench tomorrow just in case.....

 

You'm need a French Drain to intercept the run off from next door. Wouldn't hurt to break up the iron panning and incorporate some sharp gravel too

 

Ah, I think that might prove tricky with the slope running toward the neighbours garden and our house but I'll have a look at it this morning. Thanks @Zigs

 

Well, I've stripped the weed and grass off and forked to the hard pan, breaking the pan as best I can. The ground is clayey silt sitting on top of horrid reddish sandy stuff. As with the exploratory trench only the top few inches is soaking wet. Found and salted three more leeches.
I have yet to lift the long roots, 2 or 3 feet in length and literally hundreds of them.
Plan is to get those roots out and then work in a good amount of manure. I'm not sure if I should add sand given the silty nature of the clay.
I'm not sure aiming for a lawn here is the best idea at all actually.
Back to the drawing board. Oh hum.

 

So, I went out this morning aiming to lift those roots and I am confronted with a huge pool. Clear water has filled the dug over area and there was no rain over night. I took my gardening jug and emptied as much water as I could and now it is pouring rain.

I did think about flinging a tarp over it but that would be a bit like shutting the stable door after the horse has bolted.

This new garden is proving to be extremely challenging indeed.

Still smiling though