When it comes to achieving a lush, healthy lawn, many homeowners focus on choosing the right turf variety, ensuring proper watering, and maintaining a consistent mowing schedule. While all of these factors are essential, one crucial step that often gets overlooked is the preparation of topsoil before laying new turf.
Topsoil forms the foundation upon which your grass grows. It provides essential nutrients, supports healthy root development, and ensures the right balance of air, moisture, and organic matter. Without quality topsoil, even the best turf can struggle to establish properly, leading to patchy growth, poor drainage, and long-term maintenance issues.
In this article, we’ll explore why you need topsoil before laying new turf, what makes good topsoil, how much you’ll need, and how to prepare your site for a thriving lawn.
1. What Is Topsoil and Why Is It Important?
Topsoil is the uppermost layer of soil — typically the top 10 to 20 centimetres — that contains the highest concentration of organic matter, minerals, and microorganisms. This layer is where most plant roots grow and draw nutrients for healthy development.
Good-quality topsoil should be rich, dark, and crumbly, containing a balance of sand, silt, clay, and organic material. It acts as a nutrient reservoir and a buffer that supports root growth, moisture retention, and drainage.
When laying turf, the condition of the underlying soil directly affects how well your grass will establish. Poor-quality or compacted soil can restrict root penetration, limit water absorption, and reduce oxygen availability — all of which lead to a weak lawn.
By adding topsoil, you essentially create a fertile and balanced growing medium that gives your new turf the best chance to thrive.
2. Benefits of Adding Topsoil Before Laying Turf
Improved Nutrient Availability
Topsoil provides essential nutrients such as nitrogen, phosphorus, potassium, and trace elements that support strong grass growth. Turf laid on nutrient-depleted ground will struggle to take root and may quickly yellow or thin out.
Adding topsoil ensures your lawn receives a consistent nutrient supply, helping it establish faster and remain greener for longer.
Better Drainage and Moisture Retention
Proper drainage is vital for turf health. If the underlying soil is too compact or clay-heavy, water can pool on the surface, leading to root rot or fungal issues. Conversely, sandy soils may drain too quickly, depriving roots of the moisture they need.
Topsoil creates a balanced structure that improves both drainage and water retention. This balance keeps the turf hydrated without becoming waterlogged, promoting stronger root development and disease resistance.
Enhanced Root Growth
Turf roots need soft, well-aerated soil to grow deep and anchor firmly. A layer of topsoil encourages roots to spread out evenly, making the grass more resilient to drought and foot traffic.
Without topsoil, the turf may only develop shallow roots, leading to a weak lawn that dries out quickly and is prone to damage.
Easier Turf Installation and Levelling
A smooth, even surface is crucial when laying turf. Topsoil allows you to level uneven ground, fill in low spots, and create a consistent base for installation.
This not only makes the turf easier to lay but also ensures that water drains evenly across the lawn, preventing puddles and dry patches.
Long-Term Lawn Health
Topsoil improves soil fertility and structure over time, ensuring your lawn stays healthy and vibrant for years. It supports beneficial microorganisms that break down organic matter, aerate the soil naturally, and make nutrients more accessible to grass roots.
3. How Much Topsoil Do You Need?
The amount of topsoil required depends on the existing soil quality and the condition of your lawn area.
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For poor or compacted soil: You’ll typically need a layer of 100–150mm of good-quality topsoil to provide a healthy growing medium.
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For reasonably good soil: A lighter layer of 50–100mm may be sufficient to refresh the surface and improve fertility.
To estimate how much topsoil you’ll need, multiply the area (in square metres) by the depth (in metres) to get the volume in cubic metres.
Example:
If you’re covering a 50m² area with 100mm (0.1m) of topsoil:
50 × 0.1 = 5 cubic metres of topsoil.
Always order a bit extra to account for settling and levelling.
4. Choosing the Right Topsoil for Turf
Not all topsoil is created equal. The right blend can make all the difference in how well your lawn establishes.
Turf Underlay Mix
For turfing, it’s best to use a turf underlay soil mix — a blend of loam, sand, and organic matter designed specifically for turf establishment. This mix ensures good drainage while retaining enough moisture for healthy growth.
Check for Contaminants
Make sure your topsoil is weed-free and contaminant-free. Poor-quality or recycled soil can contain weeds, stones, or construction debris that hinder root development.
pH Balance
Grass generally prefers a neutral to slightly acidic soil, with a pH level between 6 and 7.5. If unsure, you can test the pH of your topsoil and amend it with lime (to raise pH) or sulphur (to lower pH) as needed.
Organic Content
Good topsoil should contain at least 5% organic matter, such as compost or decomposed plant material. This helps improve structure, moisture retention, and microbial activity.
5. How to Prepare the Ground Before Adding Topsoil
Proper site preparation ensures your turf roots have the best possible environment to grow.
Step 1: Remove Existing Grass and Weeds
Clear the area of old turf, weeds, and debris. Use a turf cutter or herbicide if necessary, and remove rocks, sticks, or rubbish that may interfere with levelling.
Step 2: Loosen the Soil
If your existing soil is compacted, loosen it with a rotary hoe or garden fork. Breaking up the soil to a depth of about 100–150mm helps improve drainage and root penetration.
Step 3: Add and Spread the Topsoil
Spread your topsoil evenly across the area. Aim for a consistent depth of 100mm for most installations. Use a rake to level the surface and fill in any low spots.
Step 4: Level and Compact Lightly
After spreading, lightly compact the soil with a roller or your feet to remove air pockets. Be careful not to over-compact it — you want it firm enough to walk on without sinking, but still soft for root growth.
Step 5: Water and Settle
Lightly water the soil to help it settle. Allow it to rest for a day or two before laying your turf to ensure an even surface and optimal moisture levels.
6. Laying Your New Turf
Once your topsoil is prepared and settled, you’re ready to lay your turf.
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Start from a straight edge, such as a driveway or garden bed, and work your way across.
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Stagger the joins like brickwork to prevent visible seams.
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Press down firmly on each roll to ensure good contact with the soil.
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Water immediately after installation to help the turf bond with the topsoil and encourage root establishment.
Continue watering daily for the first couple of weeks, gradually reducing frequency as the turf takes root.
7. Common Mistakes to Avoid
Even with good topsoil, certain mistakes can undermine your efforts:
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Using too thin a layer of topsoil: Anything less than 50mm may not support root development.
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Skipping soil preparation: Laying turf directly on hard or uneven ground leads to poor results.
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Ignoring drainage: Without proper slope or soil composition, you risk water pooling.
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Choosing poor-quality topsoil: Cheap or contaminated soil can introduce weeds and stunt turf growth.
Taking the time to properly prepare and use high-quality topsoil will prevent these issues and save you money in the long run.
8. Long-Term Lawn Care Tips
Once your turf has established, maintaining healthy soil remains essential for its longevity.
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Fertilise regularly: Apply a slow-release lawn fertiliser every few months.
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Aerate annually: Aerating loosens compacted soil, allowing oxygen and nutrients to reach the roots.
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Top dress occasionally: Adding a thin layer of topsoil every year helps replenish nutrients and maintain level ground.
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Water deeply but infrequently: This encourages deeper root growth and greater drought resistance.
By continuing to care for your topsoil, you ensure a strong foundation for a lush, green lawn year-round.
Final Thoughts
Laying new turf isn’t just about choosing the right grass — it’s about creating the right environment for it to grow. Topsoil plays a vital role in establishing a healthy lawn by improving nutrient content, drainage, and soil structure. Whether you’re starting from scratch or revamping an existing yard, investing in quality topsoil before laying your turf is one of the smartest decisions you can make.
A beautiful, long-lasting lawn starts from the ground up — literally. So before you roll out that fresh green turf, make sure your soil is ready to nurture it to perfection.
For premium-quality turf and soil supplies, contact A View Turf Supplies in Sydney. They provide topsoil, turf varieties, and expert advice to help you achieve the lawn you’ve always wanted.
