You cannot lay sod over your existing grass. The new sod won’t be able to take root in the soil because the existing grass will block the sod roots from making soil contact. This will cause your new sod to dry out and die in many cases. Meanwhile, the old grass underneath the sod will die and begin to turn slimy, but it won’t decompose quickly. Dry sod and slimy, dead grass underneath creates the perfect conditions for invasive weeds and fungal lawn diseases. Plus, raising the height of your lawn by adding new sod on top of grass can cause water to flow from your lawn onto your paved surfaces, which creates a flooding problem.
7 Dangers of Laying Sod Over Bad Grass
It may be very tempting to simply install new sod on top of your grass and establish a green lawn that way. However, this method will backfire. Here’s what will happen if you lay sod over bad grass, weeds, or any other plant growth.
Your New Sod Won’t Take Root
Sod requires sod-to-soil contact in order for the sod to send roots down into the dirt. If you lay sod on top of bad grass, the grass will form a barrier of blades, stems, and roots that prevent the sod from getting a foothold in the soil. If your sod can’t develop healthy roots, it won’t be able to gather its own water and nutrients from the soil. So, your sod will struggle and fail.
The New Sod Will Dry Out
Sod is delivered with a very thin layer of topsoil accompanying the grass. This is where the sod gathers all its water until it begins to take root. Because your sod can’t take root when it is installed on top of bad grass, this thin layer of soil is extremely prone to drying out during any hot, dry periods. If you lay sod over grass, it’s very likely to turn brown and die once temperatures rise.
The Old Grass Will Turn Slimy
Bad grass under sod will not decompose well. Instead, the fibrous roots and stems of the grass will become yellow, slick, and slimy. The layer of dead grass under the sod can become so slick that the sod may slide over the grass when you walk on it. If your sod dries out and dies, you’ll be left with a lawn of dead, slimy grass.
Fungal Diseases May Attack
By laying sod over existing grass, you invite pests and diseases to your yard. The layer of slimy, dead grass under your sod is the perfect breeding ground for pest insects and fungal diseases. Insects destroy your sod and garden. A fungal disease that forms on dead grass under your sod can spread across your yard. In addition to your other troubles, you may have a fungus or lawn rust that spreads from your bad grass to your new sod.
Weeds Will Invade
As the bad grass under your sod dies and the sod above dries and shrinks, gaps will form between the pieces of sod. This is the perfect place for weeds to sprout and begin taking over your lawn. In most cases, laying sod over existing grass leads to dandelions, crabgrass, and other types of weeds invading the yard while the sod struggles.
Your Lawn May Flood
Laying sod over existing grass increases the height of your yard by 1–2 inches (2.5–5 cm). This may not seem like a problem, but it can cause significant flooding issues. Raising the height of your lawn by adding sod on top of grass causes water to flow from your lawn onto your driveway, patio, and other paved areas. The standing water can remain for days. Installing sod over grass can even cause flooding and erosion around your home’s foundation.
It Will Cost You
Whether your sod dries out and dies because it cannot take root, or if your lawn is attacked by weeds and disease, laying sod over bad grass will end up costing you time and money in the long run. Sod can be expensive. If sod dies in areas where it was laid over grass, it will take work to remove the dead sod and buy more for the area. So, you’ll save yourself money by removing grass before you install sod.
Do You Have to Remove Old Grass Before Laying Sod?
It is essential to remove old grass and get rid of weeds before you lay your sod. By removing the existing plant material, you allow the sod to make contact with the soil. This encourages fast sod rooting, which means your sod will become much more self-sufficient much faster. Preparing your lawn by removing any old grass is essential if you want your sod to develop into a healthy lawn.
- It is required to remove any existing grass before you lay sod.
- A sod cutter is the tool used for removing grass before installing new sod.
- You can rent a sod cutter at most local home and garden centers.
The best way to remove old grass is by using a sod cutter. If you’re not familiar with these tools, check out our easy steps for using a sod cutter yourself. A sod cutter will remove the grass, along with a thin layer of topsoil and root material. Then, you can till and level your yard to make it the perfect habitat for new sod.
How Do You Replace Bad Grass with Sod?
Replacing bad grass with new sod is a multi-step process. First, you need to use a sod cutter to remove the existing lawn, which can then be thrown away. Next, you need to till the soil to a depth of 6 inches (15 cm). Once your soil has been loosened, you can begin taking more specialized steps to improve soil quality and prevent weeds from invading your sod. Our complete guide to preparing your lawn for sod installation contains all the information you need to replace bad grass throughout your entire lawn.
- Use a sod cutter to remove existing grass.
- Till the soil to a depth of 6 inches (15 cm).
- Test and prepare your soil with compost, lime, or other additives,
- Roll and level your soil so you have a smooth lawn.
- Calculate the amount of work required to lay your sod and get some helpers.
Once your lawn is prepared, you’re ready to order and install your sod. You can have sod professionally installed or you can do it yourself. However, installing a whole lawn’s worth of sod is a big job. So, make sure to enlist some helping hands. Sod shouldn’t be left on a pallet overnight, so the sod will all need to be laid in one day.
Can You Cover Existing Grass With Sod?
Grass cannot be covered with new sod. Doing so will result in disaster for your sod and your lawn in general. Here’s what will happen if you lay sod over old grass:
- The sod will not be able to take root because the old grass will block the sod roots from reaching the soil.
- The new sod will dry out since it cannot develop roots and pull water from the soil.
- The old grass will die and begin to turn yellow and slimy.
- The slimy layer of old grass will attract insects and fungal diseases.
- Weeds will invade your lawn while your new sod struggles.
- Sod laid on top of grass will increase the height of your lawn, which can cause water to flood your driveway, other paved areas, or foundation.
- You will end up paying more if you have to replace sod that dies.
It is always required to fully remove old grass and any other plants before installing sod. Taking the time to prepare your lawn ensures your sod has the greatest chance of survival. This will eliminate the risk of a failed sod installation.