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How much soil does grass need?

If you are laying or seeding a brand new lawn then you may be wondering how deep you need to go with your topsoil, after all, how much soil does grass need?

How much soil does grass need
How much soil does grass need?

The answer to this question depends on a few factors, firstly what is the topsoil going onto? If it is going onto soil then you don’t need much at all 1-2 inches will probably do the job.

If you are going onto something else like sand or hardcore laid down after some reservation work then you will need much more. Grass will grow in 6 inches of topsoil on top of another surface but this does not mean it will look its best.

You should really be aiming for 12-18 inches of soil for your grass to grow into. This will make sure there is plenty of room for the roots to reach down into and also plenty of material to aid with drainage.

Grass will grow in pretty much anything, it can grow in a thin layer of soil less than a cm thick. But growing anywhere and growing and being suitable for a lawn are two different things.

When growing grass for a lawn it is obviously going to be under frequent stress with being cut roughly once a week and never being allowed to grow to any sort of length. To support this life cycle a lawn needs really strong roots and for a strong root system to form you need plenty of depth.

Can I put topsoil over an existing lawn?

Yes, you can spread topsoil onto a lawn without issue. As long as you don’t go really deep with your topsoil then the grass will just grow through this new layer of soil and in any patches where it doesn’t you can just throw down some new seed, which leads me on nicely to my next point.

Can I just throw down grass seed?

Yes, you can simply throw grass seed down. This is often how I put my grass seed down, just with the seed in the palm of my hand and moving my hand back and forth in an arc. Just let the seed fall out of your hand naturally and you will find you distribute it reasonably evenly.

How do I fix a bumpy lawn?

One quick and easy way to fix a bumpy lawn is to chuck some topsoil down in the dips and then sow some new seed into it. You can put the top seed down and then level it with a lute if you have one or a rake or simply a big piece of wood almost as if you are screening concrete.

In the dips you will want to press the topsoil down before seeding, otherwise you may find it dips again as the new topsoil is compacted.