Topsoil calculations and advice needed

[ABCwarrior]

Hi,

Our house is in a forest clearing in the highlands upon glacial till- ie lots and lots of boulders and gravel with patches of sand. Remnants of the ice age!
The garden is just a mammoth task we have no soil whatsoever as it's just forest detritus in places, stumps and more gravel. One side of the house we want to have grass on and I've calculated the area out at 175m sq. Is 100mm thick soil ok for this to be seeded? I found a site that says loose soil is 1.25t, compacted is 1.7t per cubic metre so on the compacted basis we would be looking at 30 tonnes. The local quarry does soil delivered at £14 a tonne plus vat and given our restricted access 2 loads at 17t would be just under £600 and allow a bit of extra.
What would 100mm loose compact down to? Is it enough? We won't get a perfect lawn I'm sure and I doubt the "local" soil will be nutrient rich but the stuff on the net at £80+ per tonne bag is out of the question!

 

[RedHerring2]

First off, I don't think you can buy soil on a compacted basis. This refers to the undisturbed soil in the ground, as soon as you disturb it, to load into bags or onto a lorry, it becomes uncompacted soil.

Theoldun did an excellent compaction ratio for various types of soil.

Looking at your figures it looks like a compaction ratio is about 1.36.
So 100mm uncompacted will compact down to about 73mm.

 

[ABCwarrior]

Cheers for the reply, gonna get the two loads of 17t and use this on the area that should give close to 150mm when down, a neighbour has a roller and advised to then roll it, rake it, seed it and then roll it again- so if it drops down to near 100mm that's ok. Spent 9 hrs today digging and removing boulders from all sizes up to football sized ones, plus rotting tree branches/stump remains it's relentless but the end is nearly in sight on this part. We have half an acre of this crap and there's bits which I will probably never touch. Need to start bagging up molehills and spreading them around the garden to fill in voids etc!
After the manual graft I've put in on this side of the house it would be daft to spread the soil thin for maximum area coverage cos at least the ground should be easier to level and won't be too stony once the roots lock the soil up into a big thick carpet....

 

[RedHerring2]

Having done some spoil spreading in France after digging out for the patio, I'd be tempted to roll it, rake it, then let it settle for at least a couple of months, then rotovate it before seeding it.

When the soil is tipped and spread around you'll still have clumps that are already compacted because they didn't break up in the process. There'll also be voids of uncompacted soil which will settle in time and you're left with a very uneven surface.

I take it, that you're using machinery to spread the soil, 'cos that's a lot of soil to spread. In which case you'll have some compacted areas again from the weight of the digger or similar.

If you can't wait for a couple of months, at least rotovate it before seeding it.

 

[ABCwarrior]

It's a race against time so probably need to get it down and seeded by the end of the first week in May, it's getting spread manually(looking forward to that need to be there when it's delivered and hope the driver is competent enough to drop it and move simultaneously). The spring has only just started here but I've read in colder climes it's sometimes better to seed in the autumn so the ground is warmer.
I'd rather seed it in late August/September but the OH is nipping my head about getting it done!

 

[MFCGMFC]

if you seed in the autumn then by the time your grass comes up it will be getting into winter which will damage new grass

get it done asap so it has a bit of strength and the best growing conditions availble through may june july august

never leave it as late as august september for seed

 

[r896neo]

Sowing in autumn is good for grass, in fact it is better as the weeds grow less and it will establish roots rather than length.

I have sown lawns in late september which have taken well.

 

[LooPrEvil]

Neo is correct, but note the OP is based in Inverness, where they can get frost /snow in early September. I would therefore opt for a spring seeding.

 

[ABCwarrior]

The day was a scorcher yesterday. Minus 4 at 6am when off to work so still winter temps when clear skies at night- time yet to get it down, called the quarry today Friday it's getting delivered better start limbering up

 

[MFCGMFC]

Sowing in autumn is good for grass, in fact it is better as the weeds grow less and it will establish roots rather than length.

I have sown lawns in late september which have taken well.

poor growing rates, no?

for the OP's location as early as possible summer seeding would be the best?


for every 100 mile south its 1 degree warmer...so the OP must be artic conditions lol!

 

[ABCwarrior]

Aye sure is- we're about 255m above sea level but being in the Spey Valley within the Cairngorms/Monadliaths and unless we get freak inversions the cold air drops down to our level, which is only 10-15m above the valley floor at Loch Insh. It was -6 in the mornings late last August so our "growing" season is certainly shorter than the UK average! I work down in Perth and on any given day there's a diffference of usually 5 degrees....Buds are only just showing here yet down in St Andrews at my mums yesterday and all is exploding into life.
The brother in law lives in Portsmouth and he said spring started about late January.... !!!