If you have a large patch of concrete on your property that you want to get rid of, it can be tempting to consider simply covering it with grass rather than going to the expense and effort of removing the concrete. However, it’s not an easy fix to your concrete problem.
Can You Grow Grass Over Concrete?
It is possible to grow grass over concrete, but it requires considerable preparation before you get to the stage of laying down sod or sprinkling grass seed over top. You will need a thick layer of soil to give the grass the best shot at maintaining healthy growth over the long run.
What Should You Consider Before Growing Grass Over Concrete?
Before growing grass over concrete, you need to take a few key factors into consideration. That includes the location of the concrete in your yard, its condition, and the intended use of your planned patch of new grass.
If the concrete pad you want to cover with grass is right next to the house, it may not be possible to simply cover it with lawn. If the new layer of soil and grass is so high that it is in contact with your brick, wood, or vinyl siding, you will have moisture damaging the siding material and seeping through into your walls.
Even if it’s not right next to your house foundation, the increased height of the grass-covered concrete is going to stick out above the level of the surrounding lawn, which will look awkward and be difficult to mow.
If the concrete that you want to cover with lawn is in poor condition, that can create real problems down the line. If portions of the concrete pad shift, you will end up with a patch of grass that is pitted with unexpected dips and holes.
Certainly in the short term, you won’t be able to use the grass-covered concrete for heavy traffic, and it may never have enough resilience to withstand uses such as a playground.
Not looking to grow over solid concrete? We have a related post “The Minimum Soil Depth for Growing Grass Over Rubble” here.
What’s the Minimum Soil Depth for Growing Grass Over Concrete?
The term “soil” in this context should include not just the topsoil, but also a layer of sand and gravel underneath actual dirt. This improves drainage in the long term, and also gives the grass roots extra depth to grow into.
That being said, you should be laying down a soil layer of at least 4 inches (10 cm), with a couple of inches of gravel underneath that. That gives you a total depth of 6 inches (15 cm) above the level of the concrete.
This will give the grass roots plenty of room to stretch out into, and provide enough soil mass to keep it from drying out too fast. While grass plants cannot tolerate soggy, poorly-drained soil, they also need consistently moist soil.
How Much Fill Dirt Should You Lay?
The more fill you lay down on top of the concrete, the better your drainage will be. Aim for at least 2 inches (5 cm) of very loose, porous soil mix, or even fine gravel. Spread it out evenly across the entire surface. If there are any holes or dips in the concrete, use this fill to create a level surface for the topsoil.
How Much Topsoil is Required?
The topsoil is the key to the healthy growth of your new patch of lawn, so get the best quality possible. Lay down a layer of at least 4 inches (10cm). While theoretically turf grass can grow in as little as 1 or 2 inches (2.5-5 cm) of soil, it will quickly dry out and require lots of watering on an ongoing basis.
Take a look at how your layers should look:
Is it Better to Lay Sods or Plant Grass Seed When Growing Grass Over Concrete?
Just like with a regular lawn, you can use either sods or grass seed when growing grass over concrete. Seed will take longer to form a dense, resilient mat over the concrete, but sod is more expensive. However, if you are dealing with a fairly small area to be covered, that’s not as big of an issue.
Tips for Growing Grass Over Concrete
1. Drainage Is Crucial
Without good drainage, your new patch of grass is going to drown and die. Excess water will not drain through, but will instead pool on the surface of the concrete, engulfing the grass roots and cutting off the air they need for healthy growth.
If you can drill holes straight through the concrete to the ground underneath, that will give water somewhere to go. You can also score the surface of the concrete with deep grooves that will carry away water so that it can sink into the surrounding ground.
Finally, laying down a layer of gravel or rough fill on top of the concrete will keep the water from saturating the topsoil and drowning the roots.
3. Use Nutrient Rich Soil
If you want a thick, lush patch of lawn growing on top of your concrete, you need to provide a rich soil full of nutrients and organic matter to maintain healthy growth.
Use the best quality topsoil that you can get, and for even better results mix in a good quantity of well-rotted compost or leaf mold. Not only will this help feed the young grass plants, but also will maintain soil moisture longer than a mix with less humus.
4. Water Appropriately
Whether you have sown seed or rolled out sods atop your layer of topsoil, it’s essential to keep your new grass well watered, but not too much.
There’s a fine line between saturating the soil, causing the roots to drown and the blades of grass to turn yellow, and letting the soil dry out, with the blades turning brown and brittle. Once you’ve set the sprinkler to water the new grass, check to see how deep the water has penetrated the soil. If it’s moist right down to the concrete, that’s enough.
5. Avoid Heavy Traffic Early On
Eventually, you will want to use the area where you’ve planted grass over concrete, but don’t be too impatient. Give the new turf time to develop a good, strong root system to withstand heavy traffic.
What are the Pros and Cons of Growing Grass Over Concrete?
Especially if you have a yard that is almost entirely paved, as often happens on small city lots, growing grass over concrete will add considerably to the beauty of your property. Grass will stay cooler in summer than an expanse of concrete baking in the sun, and help create a more natural oasis for relaxing in.
As well, the fewer hard surfaces in your yard, the better run-off after a rainstorm will be managed. As long as you’ve created adequate drainage under the new lawn, the water will be absorbed back into the soil, rather than running off into drainage systems.
However, there are downsides to growing grass over concrete. You will need to spend money on fill and a deep layer of topsoil to create an adequate growing medium for these perennial plants. The concrete will need to be prepared to allow for good drainage. And in the long run, you will have to water more often, especially during hot, dry weather.
Is it Worth Growing Grass Over Concrete?
If the concrete on your property is not to your liking, then it can definitely be worth growing grass over it. Creating a lawn can give you additional space for recreational purposes, or just to make your yard more aesthetically pleasing.
However, if the concrete is in poor condition, or the increased height of the area will create problems, you should consider alternative solutions.
Alternatives to Growing Grass Over Concrete
If the concrete is in poor condition, or you can’t add several inches without creating other problems, you may need to remove the concrete altogether before seeding or sodding the area.
If the concrete is in excellent condition, consider using artificial turf instead. The newer versions work well on patios and children’s play areas. Once it’s installed, it’s virtually maintenance-free and will last for years.
Finally, consider keeping the concrete but instead of covering it all with grass, create a courtyard with raised beds. That way, you can grow a variety of flowers and vegetables, and even small trees, in containers. As long as you have at least a foot of soil in the beds, almost any plant will be able to thrive.
While concrete has its place in landscaping, you can definitely have too much of a good thing. Growing grass over concrete can add much-needed soft, living surfaces to your yard, creating a more natural environment for you to enjoy.
If you take the time and effort to give your grass the ideal conditions to grow, you can expect your new patch of lawn to thrive for many years.
Janice is a retired High School teacher who is spending her leisure years keeping busy with all sorts of projects. Aside from freelance writing, she’s an enthusiastic amateur chef, home wine maker, and tends a large raised-bed vegetable garden, while at the same time running a Bed & Breakfast.