Figuring out how to prepare ground for artificial grass is arguably the most important part of the whole project, even more than laying the actual turf. If you rush the prep work, you'll likely end up with a lumpy, poorly draining mess that looks more like a carpet thrown over a gravel driveway than a lush lawn. I've seen plenty of DIY jobs where people thought they could just roll the grass out over their old lawn, and honestly, it never ends well.
Getting that perfect, flat finish requires a bit of elbow grease and a clear plan. It's not just about getting things level; it's about making sure the ground stays that way for the next decade. Here is exactly how to get your garden ready for its makeover.
Start by Clearing the Old Surface
The first thing you need to do is get rid of whatever is currently there. Usually, this means digging up your old, tired lawn. You'll want to remove the turf and about 75mm to 100mm of the soil underneath. This depth gives you enough room for the sub-base and the laying course without the final grass height being way too high.
If you're dealing with a small patch, a sharp spade and some grit will do the trick. But let's be real: if you're doing a whole garden, rent a sod cutter. It'll save your back and make the job ten times faster. You want to make sure you've removed any large stones, roots, or debris. If you leave a big tree root in there, it might eventually rot or shift, causing a dip in your beautiful new lawn later on.
Addressing the Drainage Issues
Before you start pouring in rocks and sand, take a look at how your garden handles water. If your lawn is usually a swamp after a light drizzle, you need to fix that now. Artificial grass is porous, so water goes right through it, but if the ground underneath is solid clay that doesn't budge, the water will just sit there.
In most cases, the standard sub-base provides enough drainage. However, if you have severe pooling, you might want to install a simple soakaway or some perforated drainage pipes. It's a bit of extra work, but it beats having a "pond" in the middle of your grass every time it rains.
Installing the Weed Membrane
Once you have a clean, excavated area, it's time for the weed membrane. Some people like to put this on top of the sub-base right under the grass, but putting it at the very bottom—on top of the raw soil—is often a better shout. This prevents the sub-base materials from mixing with the dirt below.
Make sure you overlap the edges of the membrane by about 10cm to 15cm. You don't want a single gap where a stubborn dandelion can find its way through. Pin it down so it doesn't shift around while you're shoveling in the heavy stuff.
Creating a Solid Edging
You need something to keep everything contained and give you a solid point to nail or staple the grass to later. Without a proper edge, the base materials can migrate over time, and the edges of your grass will start to curl or lift.
You've got a few options here: * Pressure-treated timber: Cheap and easy to work with, though it can eventually rot after many years. * Composite plastic lumber: It's more expensive but will basically last forever. * Everedge or metal edging: Great for curved borders. * Concrete or brick: If you already have a patio or a wall, that works as a perfect edge.
Make sure your edging is set at the height you want the "soil level" of the grass to be. Remember, the grass blades will sit slightly higher than the edge itself.
The Sub-Base: MOT Type 1
Now we're getting into the heavy lifting. To ensure your ground is stable, you need a layer of MOT Type 1 or a similar crushed stone. This provides the structural integrity of the lawn. You want a layer about 50mm to 75mm thick.
Don't just dump it in and hope for the best. Spread it evenly with a rake. The goal here isn't to make it perfectly smooth—Type 1 is chunky and awkward—but you want it generally level.
The Most Important Step: Compaction
If you take one thing away from this, let it be this: you must use a power compactor. Walking over the stones with your boots isn't enough. Rent a vibrating plate compactor (often called a wacker plate) from a local tool hire shop.
Go over the entire area multiple times, moving in different directions. You want that sub-base to be rock solid. If you can push your thumb into the stones and they move, you aren't done yet. A poorly compacted base is the number one reason artificial lawns fail; they end up with "footprints" and dips within six months.
The Laying Course: Sharp Sand or Grit
Once your Type 1 is solid, you need a smoother layer on top to fine-tune the levels. Most people use sharp sand, while others prefer granite dust (also known as 0-6mm screenings). Granite dust is often better because it binds together more firmly than sand, but sharp sand is more common and perfectly fine for most domestic gardens.
Apply about 20mm to 25mm of your chosen material. Use a long, straight piece of timber (a screed bar) to level it out. You're looking for a smooth finish, but it doesn't have to be "pool table" flat—a slight fall to help water run off is actually a good thing. Give this layer a quick pass with the compactor too, just to firm it up, but don't overdo it or you'll lose that smooth surface.
Final Checks and the Optional Second Membrane
Before you even think about unrolling the turf, walk around the perimeter. Check that the sand is flush with your edging. If you have any high spots or deep grooves from the compactor, smooth them out with a hand trowel.
Some installers like to put a second, thinner weed membrane on top of the sand right before the grass goes down. This is mostly to prevent the "crunchy" sound of the grass backing rubbing against the sand. It's not strictly necessary, but it's a nice touch if you want a premium feel.
A Quick Word on "Over-the-Concrete" Prep
If you aren't laying on soil but instead want to know how to prepare ground for artificial grass over an old patio or concrete, the process is way simpler. You don't need to dig anything up. You just need to make sure the concrete is clean and drains well.
If there are puddles on the concrete now, you'll need to drill drainage holes (about 10mm wide) and fill them with pea shingle. If the concrete is really uneven, you might need a self-leveling compound or a 10mm "shock pad" underlay to stop the pattern of the paving stones from showing through the grass.
Wrapping Up
It sounds like a lot of work, and honestly, the prep is about 80% of the total labor. But once the ground is firm, level, and draining well, the actual "laying the grass" part is a total breeze.
Taking the time to dig out the soil, build a solid MOT Type 1 base, and compact it properly ensures that your lawn looks great for years. You won't have to worry about weeds, sinkholes, or weird bumps. Just a perfectly green, low-maintenance space that's ready for the BBQ season. Now that the hard part is out of the way, you can finally get to the satisfying part: rolling out the green!