Does Sod Need Topsoil? [5 Steps to Test and Add Topsoil]

You need to add topsoil before laying sod if your existing topsoil is less than 2 inches (5 cm) deep and the soil below that is mostly clay or sand. Sod will struggle to root in extremely sandy or clay soil, so adding topsoil will help your grass flourish. Topsoil can also be used in cases where your yard needs to be leveled.

If you have rich topsoil that has low sand and clay content, topsoil may not be necessary before laying sod. When adding topsoil, add high-quality soil and spread it evenly to promote healthy sod growth.

How to Tell if Your Lawn Needs Topsoil Before Sod

Sod requires 4–6 inches of loosened, healthy soil in order to develop deep roots and transition into an established lawn. If your existing soil is of high-quality, tilling will be enough to prep your lawn for sod. But if you have low-quality soil, laying sod on top of it is a death sentence. To determine if you need to bring in topsoil, look for the following signs.

Signs Your Lawn Needs Topsoil Before Laying Sod

First, remove the existing grass and weeds with a sod cutter. Then, test your soil. To do so, use a shovel to dig several small holes, 6 inches (15 cm) deep at different areas in your yard. Look for these indicators that topsoil is needed:

• There are less than 2 inches (5 cm) of dark topsoil over sandy or clay soil.
• Previous grass struggled or died, especially in hot or dry conditions.
• Soil is hard-packed and dry less than 3 inches (7.5 cm) below the surface.
• Yard has uneven areas that need to be leveled.

If any of the above is true, you should spread additional topsoil before laying sod. This quick test will save you time and money by ensuring the sod you install survives.

Signs Your Lawn Does Not Need Topsoil

Not all lawns need topsoil before new sod can be installed. In regions with loamy, rich soil, adding new topsoil isn’t necessary. Here are the signs your yard doesn’t need any additional soil:

• There are more than 2 inches (5 cm) of dark topsoil before the soil transitions to sand or clay.
• Previous grass grew well when properly watered and fertilized.
• Soil is not extremely hard to dig and retains moisture down to at least 3 inches (7.5 cm).
• Your yard is level, without many dips or rises.

When your soil is already moist and rich with loam and organic material, it has all it needs to allow your sod to take root. If this is the case, you can take steps to prepare the ground and lay sod without any additional topsoil.

5 Steps to Add Topsoil Before Installing Sod

If you have determined your yard needs topsoil, it’s time to get the job done right so your sod can take root and thrive. The process isn’t as simple as dumping new soil on your yard and laying sod on top. To create a pristine new sod yard, follow these steps:

Choose Good Topsoil

The best topsoil for sod is dark brown to black in color, even when dry. This coloration signifies high levels of organic matter in the soil, which means the soil will be full of nutrients and microbes that fuel grass growth.

• Look for dark brown or black soil.
• Soil should be free of debris (sticks, roots, mulch, large stones).
• Soil can have small rocks, 2–3 inches (5–7.5 cm) long.

Topsoil that crumbles easily in the hand, is free of undecomposed vegetative matter, and is dark when dry is the best for the job.

Excavate Old Soil

Before laying sod, it’s essential that the soil level is 1 inch (2.5 cm) lower than concrete surfaces such as driveways, patios, and sidewalks. If the soil level is too high, the grass will be higher than the paved surfaces after installation. This will cause paved areas to flood during rain or watering. To avoid this:

• Remove old soil along with existing grass. Make sure the soil level will be 1 inch (2.5 cm) below paved surfaces after adding 2–4 inches (5–10 cm) of topsoil.
• Discarded soil can be loaded into a dumpster for disposal.
• Use unwanted soil to fill dips or create raised garden beds.

Spreading several inches of new topsoil directly on top of old soil can increase the height of your yard, which can be detrimental to your home, garage, paved areas, and other structures. To keep your yard from being swallowed by dirt, make sure you make room for the new topsoil first.

Spread 2–4 Inches of Topsoil

Depending on your soil quality, you will need to add different amounts of topsoil. Here’s where your previous soil test comes in handy again.

• If there is 1–2 inches (2.5–5 cm) of good existing topsoil in your yard, 2 inches (5 cm) of topsoil is necessary.
• If there is less than 1 inch (2.5 cm) of good existing topsoil in your yard, spread 4 inches (10 cm) of topsoil.
• If spread at 2 inches in depth, 6 cubic yards of topsoil covers 1,000 square feet of yard.
• If spread at 4 inches in depth, 12 cubic yards of topsoil covers 1,000 square feet.
• Spread new topsoil with wheelbarrow, shovel, and rake.

By spreading 2–4 inches of new topsoil, you will add enough rich soil that, when mixed with existing earth, creates a nutrient-rich habitat for new sod. Measure your yard and order topsoil accordingly, to make sure you have an even layer of topsoil across every square foot.

Till Topsoil Into Existing Soil

Now that your new topsoil has been spread, it’s time to mix it into your existing soil. This performs two functions. First, it loosens the hard-packed soil underneath your new topsoil, making it easier for your sod to take root. Second, it mixes the high-quality topsoil with lower quality soil, distributing organic matter and nutrients through your yard.

• Use a rototiller to till the top 6 inches (15 cm) of soil.
• Make sure the new topsoil is thoroughly mixed with the existing soil.

This loosened soil will now absorb watering and fertilizers much more easily, while hard-packed soil often forms a hard, dry, nutrient-poor barrier that prevents sod grass roots from developing.

Level/Roll New Topsoil

Recently tilled soil is too loose to lay sod directly. Plus, it’s prone to settling in uneven ways. To make sure the soil is the right consistency for sod, it’s essential to roll and level the yard. To do so:

• Use this lawn roller to level and firm up recently tilled soil.
• Rake and re-level any dips or rises revealed by rolling loosened dirt.
• After successful lawn rolling, the soil should be firm enough that footprints sink 1/4 inch (1 cm) into the soil.

Once you finish this step, it’s time to lay your new sod lawn. Arrange your sod delivery, make a plan to install your pallets of new sod, and order any new lawn fertilizers you’d like to use.

Do You Need to Put Topsoil Down Before Sod?

Before laying sod, topsoil should be added to lawns where the soil contains high levels of clay or sand. These soils resist grass rooting. Your sod is prone to drying out and dying if laid directly on top of poor soil. If your yard needs topsoil, do the following:

• Choose a dark topsoil that crumbles easily in the hand.
• Remove old soil to ensure adding topsoil won’t raise the lawn’s height and cause flooding.
• Spread 2–4 inches of topsoil evenly throughout your yard.
• Till the top 6 inches of soil to mix new topsoil with the existing soil.
• Use a lawn roller to firm and level tilled soil.

Once these steps are complete, your yard is ready for the next steps of sod installation, watering, and fertilization. Within weeks, your sod will have developed healthy roots in the fresh new topsoil.