Laying sod (grass) over gravel can be an easier alternative to completely removing the gravel. However, there are some preparations you need to consider before you go ahead and do it. So, let’s look at these.
The most basic reason why you might want to lay sod over gravel is that you don’t want to remove it. For example, you might want to lay a lawn over a gravel garden or driveway without completely removing the existing structure.
Another advantage is that gravel is perfect for draining water. As such, it can help if you plan to lay a lawn in a rainy area or in the path of a water stream. In these instances, it might be a case of laying your own gravel first.
Once you’ve prepped the area, laying sod over gravel isn’t drastically different from any other lawn-laying process. Equally, there’s basically only one way of laying sod over gravel after the prep stage (which you can do in 1 of 3 ways).
The first step is to prep the area, and the process will differ depending on what you’re working with.
If you plan to lay sod over an existing area of gravel, there’s a high chance you’ve got a layer of membrane under it (like this). Its purpose is to stop weeds from growing through and, while it’s water permeable, it’ll stop your grass from growing properly.
Dig into the gravel to see if you’ve got a layer of membrane underneath. If so, you’ll need to remove it because the grass roots won’t grow deep enough otherwise. This’ll be a massive job and will require you to remove the gravel too. As such, you can then just follow a standard lawn-laying process.
If you’ve only got a thin layer of gravel (say, an inch or less), your best option will be to mix some loose soil into it. This’ll create a layer of stony earth, which will be fine for gravel. You can also use this method if you want to add gravel to your lawn area for drainage.
But if you’ve got a thicker layer of gravel (anything over an inch), you’ll want to start by removing the bigger stones. Next, rake the gravel so it’s even. You can then proceed with the steps below.
Next, add a layer of soil over the gravel. You’ll need 4-6 inches of soil over a layer of gravel, which should be fine for pretty much any type of grass. The purpose of the soil is to give it something to root in, as it can’t do this in gravel.
Go over it with a roller to compact the soil and even it out. This’ll give you a good foundation onto which you can lay the lawn.
Finally, lay the sod. Rake the soil lightly to break it up. Then, start in the corner furthest from your way onto the lawn and lay in strips. Fit the ends of each roll against one another without tucking them.
Continue doing this until you’ve finished the lawn, working in strips. Cut the ends of rolls using scissors or a spade.
Once you’re done, keep it moist for 3 days or so. It should be a heavy watering of 4-6 inches to encourage root growth. You can then reduce this to 1 inch until the sod is established.
You can’t install sod directly onto gravel because it won’t root properly. While it’ll likely stay alive, the roots won’t be able to draw up water, so it’ll burn out and die quickly in hot weather.
Sand is perhaps a better alternative to gravel if you simply want drainage. It’s closer to the composition of soil, so grass will root more easily.
You should add up to 6 inches of soil on top of gravel before you lay grass. If you’re mixing soil into the gravel (or vice versa), you could reduce this to 4 inches. Either way, grass needs a good layer of soil to establish itself.
Laying sod on gravel takes some prep, but it’s definitely possible. Bear in mind, though, that there are more practical ways to drain water if that’s your goal. Also, assess the area properly first, as you’ll need to remove the gravel anyway if there’s a membrane underneath.