Lawn turf and rubble query

Gareth Ramsey

Hello

I've recently removed the old, rotten decking in my back yard and was hoping to lay some turf down. However, below the decking appears to be at least 8" or more of rubble and hardcore and bits and pieces. I've been looking online at depths needed for top soil etc, and about drainage. There's plenty of drainage, but the gaps are going to mean that top soil on its own is just going to wash away when it gets wet.

I've attached an image, which hopefully will show up, and demonstrate the situation.

If I add a layer of gravel and sharp sand, then lay 6" of topsoil before adding turf, will that be sufficient to stop the soil washing away so my lawn would stay green?

 Thanks

 

Fairygirl

Hi Gareth, I think you need to get a load of finer gravel to fill in all the gaps an get a level surface on which to start. Make sure it's well consolidated then lay a layer of membrane before adding soil and then your turf. That way the soil won't get washed through into the sub base. It's important to firm it down before you put membrane down otherwise it'll still be lumpy and uneven. You just need a firm level starting point and you'll probably need a fair bit of gravel even if it's not a huge area. 

That's what I'd do anyway! 

Gareth Ramsey

Thanks for the help.  So do you think I shouldn't worry about adding sand to the gravel before covering the gravel with a membrane?

Jim Macd

HI Gareth, I'm a bit jelous, if I could have affored it I'd have had my topsoil stripped. If you want a nice fine turf, not a course turf with only rye grass and dandelions then the more impoverished the better, and you certainly won't have to worry about drainage.  I personally would put a finer garvel over the top then sand as you say followed by as little topsoil as you can get away with just to get the grass going. The grass roots will bind it all together and you could always top dress with more sand later. If you're lucky you'll have a wonderful mix of wild flowers and even orchids rather than common trefoils and thistles as weeds. I'll swap you my foot of top soil anyday. 

Fairygirl

Don't think you'd need the sand Gareth but it certainly adds drainage so no harm in using it anyway.  As Jim says too- you don't need loads of soil - unless  you're needing to raise the ground  level? Grass is shallow rooted so once you've got it established it's a maintenance job.  

Gareth Ramsey

Thanks for the replies.  I'd read that 6" was the ideal depth for top soil, is that not the case?