Compacting Soil ready for laying grass seed…..help!

We had a strip of slabs next to our lawn down the side of our garden that I have decided to get rid of and seed with grass.
The area is about 8 ft by 30ft or so. I decided we should put some grass down to join up with the rest of the garden as it is a bit of an eyesore and we’ve already got patio space across the entire back of the house.

I removed the slabs, dug the whole area over to turn the soil and then compacted and levelled it ready for seeding.
I managed to get it fairly level and tramped it down what I thought was most of the way. At the weekend I hired a roller and had a better stab at levelling it off. It took most of the day to get it level and the roller wasn’t very useful, but I got it pretty flat.

Yesterday I decided to try and tramp it down some more as there were some ‘spongy’ areas. The soil is mainly sticky clay. One end seems worse than the other, as it was a lot wetter.
Well, after a fair amount of tramping back and forth I had managed to sink a small area by a further 2″ or possibly more and it was still not ‘firm’. This took bloody ages and it is still not compacted enough in my opinion.

The roller is clearly not doing enough of a job on it and doing it with my heels as all the online guides recommend is going to take absolutely ages..
I debated hiring a plate compactor, but am concerned that on a clay soil surface it is going to sink or not work properly or just bounce around due to the ‘springyness’ of the soil.
So, I was thinking of buying one of those square metal hand tampers with a long pole and giving it a good seeing to. I don’t mind doing it ‘manually’, but am just wondering whether it will be effective enough? Or whether it’s overkill. I used one last year (hired) to compact some hardcore when filling a pond in and it worked really well. But that was a different material I was trying to bash flat.

I was hoping to get the seed down before the end of the month, but this is looking less and less likely. I don’t mind getting it prepared and leaving it until spring; I just want to make sure that the surface is prepared correctly so that I don’t have a lawn that sinks in a year or so due to rushing the preparation.

Any experience in this area or guidelines as to what I should be doing would be appreciated.

I just turned it over, bunged the seed down and let it naturally find it’s own level – what was a clear step down at the beginning of the summer is now looking much more blended.

You don’t need to stamp it all down, you need to rake it level into a fine tilth, sew the seed, rake it in and leave it. To speed it up put plastic over the top.

Compacted soil won’t drain.

Rockape63 – Member
You don’t need to stamp it all down, you need to rake it level into a fine tilth, sew the seed, rake it in and leave it. To speed it up put plastic over the top.

Compacted soil won’t drain.

Stupid question – if it sinks when walking on it at the moment – I can feel it moving, won’t I end up with loads of sunken areas in a year or two if I don’t compact it?
It feels like there are loads of air pockets under it. Most websites recommend ‘heeling it’ at least twice, but I have done that and while there are areas that feel firm, there are areas that don’t feel very stable at all.
My concern is that if I go ahead and seed it as it is, then if it does sink in a year or two it will be much more of a headache to sort out when covered in grass.

I did wonder whether compacting it too much would mess up the drainage though!

it will be much more of a headache to sort out when covered in grass.

Surely you would just bung some more topsoil on it and let the grass grow through to the new surface?

johndoh – Member

Surely you would just bung some more topsoil on it and let the grass grow through to the new surface?

Maybe? Dunno. Not much of a gardener, so I don’t know how these things are done.
Probably over-thinking the problem, as ever.

To me, it’s just a bit concerning that with a bit of stomping I have managed to drop the ‘level’ I had made by at least 2″ and it still doesn’t feel firm underfoot. The best way I can describe it, is that the surface feels like a large piece of blu-tac in places.

Another thing that makes me think it needs more flattening…… after turning it and flattening it, to get it back to the level of the surrounding grass I have had to remove a large skim of soil; a mound perhaps 3′ 6″ tall with a base diameter of 5′. This soil was previously underneath the slabs and the slabs were raised compared to the grass. Just seems wrong to have a load of ‘excess’.

build a jump out of it.

you don’t want it compacted to much it’ll be rock hard when dry, the seed won’t take as well and it won’t drain either. once the grass has taken the roots will bind it all together and firm it up

and yes you can add topsoil to fill depressions in lawns letting the old grass grow through, also bung a bit more seed on for good measure – look up topdressing

if its too compacted your seed wont grow, the grass roots will help stabalise it when its grown.

I raised my lawn by between 12 and 6 inches over a large area, over used the heels method regularly but it was still soft after the layers built up. I tried using a punner (aka tamper thing) but it quickly buggers up your shoulders, and my soil was light/chalky so I suspect clay would just stick to it.

I hired a heavy duty compactor and ran it all over for a morning (using a hosepipe to keep the dust down, but still wasn’t convinced. A year later it is fine, the deepest part of the lawn has probably dropped 2 inches where it meets a flight of steps so I’ll probably peel back a strip and add soil, or just sprinkle it over the top but I can see that taking a couple of years to build up.

I raked it after compacting to get a loose surface for turf.

Its not rocket science, yes firm it by stomping it, but once youve done that rake it gently level and seed. You’ll see in the weeks ahead it will settle, but as others have mentioned, gently even it out with some top soil without burying the new grass.

I don’t know much about gardening but I know a bit about clay.

You say you have a sticky clay. How firm or soft clay is depends on its moisture content. Trying to ‘compact it’ as you are won’t make it any firmer under foot. If you had a granular material your method would work fine.

To increase the firmness of clay you need to consolidate it. To do this you would have to apply a force over a period of time to squeeze the water out of it. A bit extreme for a lawn. I’d put something ontop of your clay to distribute the load then put your lawn on top.

I

smatkins has a point, adding some sand couldnt hurt.

OK, then. Thanks for your help thus far.

Got home and managed to take a couple of pics…please excuse the fence; painting them is on my (long) to do list.

So, here is the overall space (optional cat) with the bit I squished last night in the bottom left:

With an exciting close up here:

Which is around an inch deep off the existing patio and gets progressively deeper, although it is bulging up at the other end. That was just walking on it with my heel.

A_A, as you say…I did wonder if the grass roots would bind it all together and add some stability.

Smatkins1, yeah it’s quite a sticky clay. In fact when trying to fill some dips yesterday, the soil just sticks to my boots rather than the soil that’s already down.
I did wonder about digging in some sand, but I don’t think the rest of the garden will have been done and that seems ok (that was my reasoning for not adding sand).

The whole surface is drying now and cracking up. If I was to fill that hole in I have made and just stick some seed down, I think I will have to water it well and then rake the surface loose because as it is the seed will just bounce off!

Should have just got a bloke in to do it for me! I hate any gardening job…and it’s only getting worse the more I do!

I really wouldn’t worry too much let it dry out a bit so it’s workable, rake it level and sew the grass seed. Grass will grow on pretty much anything so by next April you’ll have a lush green patch.

If you wanted something special it would be different and a lot more prep work would be needed.

Agrees with rock ape – I bunged more seed down at the front of my house and really couldn’t be arsed with it (just a strip next to the drive and not the ‘lawn’ as such. It’s cracked on just fine.

Yeah, cheers chaps! I think that is what I am going to do…

Look out for ‘how to cure garden sinkhole’ post in 6 months!!

Its a shame you have compacted it so much already as it’ll not help the new grass to root and thrive. I would suggest just cutting the job as simply as possible, add good topsoil to existing area so it’s roughly 0.5-1 inch above the existing lawn, rake level with the back of a wide rake or hire/borrow a 4ft dragmat, and just seed.

Or, preferably, get some turf! It won’t cost much, it’ll be instant, won’t get weedy while grass seeds are germinating etc. But if you do this PLEASE don’t use B&Q. Their turf is horrendous. Last lot I got (only needed 2 rolls in a hurry) actually had dog shit in it along with the weeds, rough ripped edges, dead grass and mixed grass species.

To help the drainage, get your garden fork out and create some deep holes every six inches or so. This will stop it getting waterlogged in winter and rotting your new seed. Ideally brush sand into the holes. Do this before raking and seeding and you’re sorted!

Rockape63 – Member
To help the drainage, get your garden fork out and create some deep holes every six inches or so. This will stop it getting waterlogged in winter and rotting your new seed. Ideally brush sand into the holes. Do this before raking and seeding and you’re sorted!

Blimey! I was actually thinking of doing that!

glasgowdan – don’t fancy the idea of turf for some reason, but yeah I did wonder how well the grass will take. I think I’ll fork it over, rake another layer of soil down with some pre-seed fertiliser in it and water it in…..then I’ll seed it at the weekend…..!

The garden centre seed that’s billed as fast germinating is actually quite good and worth a try.

glasgowdan – Member
The garden centre seed that’s billed as fast germinating is actually quite good and worth a try.

Cheers for that. I’ve got some B&Q lawn seed that is billed as being quick grow, fast germinating and all that.
I chose it because it has tons of reviews and seems to be rated highly.

I also got some of their pre-seed fertiliser that I hope to put down today or tomorrow and then do the seed at the weekend.

Was late to work this morning, so really need to stay a bit later and might not get home in time to get much (if anything) done before it gets dark.

You’ll need to water loads in this weather too. At least daily.

molgrips – Member
You’ll need to water loads in this weather too. At least daily.

Yep, cheers Mol. Was planning on a quick water in the morning and a longer water in the evening. Bought a new sprinkler just for the task.

Rockape63 – Member
To help the drainage, get your garden fork out and create some deep holes every six inches or so. This will stop it getting waterlogged in winter and rotting your new seed. Ideally brush sand into the holes. Do this before raking and seeding and you’re sorted!

Blimey! I was actually thinking of doing that!

You iz a gardnerist Stumpy! 8)

Topsoil should be fluffy. Don’t stamp it down, let nature take care of its compaction through rain and gravity.

coolhandluke – Member
Topsoil should be fluffy. Don’t stamp it down, let nature take care of its compaction through rain and gravity.

Well, I raked on a top layer tonight, haven’t touched it in terms of compacting it down and just stuck a load of pre-seed fertiliser on.
Gonna seed it on Sat if the weather shapes up.

This meagre patch of grass better come up OK!! Gonna have to do a progress thread (like WCA’s shed thread) once I get the seed down…!

If it doesn’t work, I will be mainly sulking and then getting someone in, next spring who knows what they are doing 😀

All sounds very complicated- I don’t know what’s wrong with chucking the seed down and seeing what happens

johndoh – Member
All sounds very complicated- I don’t know what’s wrong with chucking the seed down and seeing what happens

Seems to be the way I go about doing things to be honest. It generally goes like this:

– ponder over the task for several weeks
– research online and get a good idea of what I need to do
– ponder some more
– buy the bits I think I need, plus some more bits just in case
– make a start and doubt I’m doing it right
– overcomplicate the task
– make a cup of tea
– ask the internet and choose only the answers that mirror closely what I am doing/have done
– finish job and wonder why it took so long
– tell myself that I’m going to do it much more simply the next time, but know deep down that I won’t.

LOL

A busy life with young kids means I never have that luxury – it’s normally half-arsed, trying to fit yet another task in around a million other things to do, throw it at the wall and see what sticks.

Gonna have to do a progress thread (like WCA’s shed thread) once I get the seed down…!

Can you setup a webcam please.

Stevet1 – Member
Gonna have to do a progress thread (like WCA’s shed thread) once I get the seed down…!

Can you setup a webcam please.

Nope. There’d be too many difficult choices to ponder and things to consider. 🙂

It’s growing….! In 6 days…!

You da Man stumpy!

I wouldn’t go that far, but cheers!! Had to shoo 3 blackbirds off it earlier!

Normal weekly grass cutting used to result in a few handfuls of clippings in the mower basket. We went away for 3 weeks in the summer, and the cut filled the bin.

After feeding, dressing and overseeding now I filled the basket twice with 10 days’ growth!