How to Measure Your Garden for Turf and How Much Turf Underlay Do You Need?

Laying turf can completely transform the look and feel of your outdoor space. Whether you are upgrading a tired backyard, renovating a property, or creating a lush green lawn for the first time, preparation and planning are everything. One of the most common questions homeowners ask before ordering turf is: “How do I measure my garden for turf, and how much turf underlay do I need?”

This guide will walk you through the process step by step. We’ll cover how to measure your lawn accurately, how to calculate turf rolls, why underlay is important, and how much of it you need for your project. We’ll also include practical tips to help you avoid costly mistakes, ensuring your turf looks stunning and thrives for years to come.

Why Measuring Matters

When it comes to turf, precision counts. If you order too little, you’ll have gaps in your lawn that may require ordering more, which can lead to mismatched batches and extra delivery costs. On the other hand, if you order far too much, you’ll be wasting money and potentially dealing with excess turf that may go to waste.

The same principle applies to turf underlay (a nutrient-rich soil mix that provides the foundation for healthy turf growth). Ordering the right amount ensures your turf establishes properly, drains well, and receives the nutrients it needs.

Simply put, accurate measurements save you time, money, and stress.

Step 1: Preparing to Measure Your Garden

Before you begin, gather a few simple tools:

• A measuring tape (a long one, ideally 30 metres if your garden is large).
• A notepad and pen for recording measurements.
• A calculator (or your phone) to make the math easier.
• Stakes and string (optional) to mark out tricky areas.

Make sure the area is cleared of any major debris so you can measure it easily.

Step 2: How to Measure Different Garden Shapes

Not all lawns are simple rectangles. Some are curved, irregular, or broken into sections by garden beds, patios, or pathways. Here’s how to measure different garden shapes:

1. Rectangular or Square Lawns

The simplest to measure.

• Measure the length and width of the area.
• Multiply the two numbers to get the total square metres (m²).

Example: If your lawn is 10m long and 5m wide:
10 × 5 = 50 m²

You’ll need 50 m² of turf.

2. Circular Lawns

Circular lawns are a little trickier, but still simple.

• Measure the distance across the widest part of the circle (the diameter).
• Divide the diameter by 2 to get the radius.
• Use the formula: Area = π × radius² (π = 3.14).

Example: If the diameter is 8m, the radius is 4m.
3.14 × 4² = 3.14 × 16 = 50.24 m²

Round up to 51 m² of turf.

3. Triangular Lawns

Some gardens have triangular patches of turf.

• Measure the base and the height (the perpendicular distance from the base to the opposite point).
• Use the formula: Area = ½ × base × height

Example: If the base is 6m and the height is 4m:
0.5 × 6 × 4 = 12 m²

4. Irregular Lawns

For irregular shapes:

• Break the lawn down into smaller, manageable shapes (rectangles, circles, or triangles).
• Measure each section separately, calculate the area, and then add them all together.

Example: A lawn with a rectangular section of 30 m² and a circular section of 20 m² would require:
30 + 20 = 50 m² of turf.

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5. Allowing for Waste

It’s always wise to add a little extra to your calculations to account for cutting and shaping the turf around edges, curves, and garden beds.

Most turf suppliers recommend adding 5–10% extra to your final figure.

Example: If your lawn area is 50 m², order 55 m² of turf to be safe.

Step 3: How to Calculate Turf Rolls

Turf is usually sold in rolls, with one roll covering 1 m² (though some suppliers have rolls slightly smaller or larger).

If your garden measures 55 m², you’ll need about 55 rolls of turf. Always confirm the roll size with your supplier.

Step 4: How Much Turf Underlay Do You Need?

Turf underlay is crucial for giving your new lawn the best start. It is a soil mix, typically containing sand, compost, and loam, that provides the perfect foundation for turf roots to establish.

The recommended depth of turf underlay is 50–100mm (5–10cm), depending on your soil type. Sandy or poor soils may need closer to 100mm, while reasonably fertile soils may only need 50mm.

Turf Underlay Formula:

Area (m²) × Depth (m) = Volume (m³)

Since underlay is usually sold by the cubic metre (m³), this formula will tell you how much to order.

Example 1: Small Lawn

• Lawn size: 50 m²
• Depth: 0.05m (50mm)
  50 × 0.05 = 2.5 m³ of underlay

Example 2: Larger Lawn

• Lawn size: 100 m²
• Depth: 0.10m (100mm)
  100 × 0.10 = 10 m³ of underlay

Tip: Always Round Up

It’s better to have slightly too much underlay than too little, as you can use the excess to level uneven spots.

Step 5: Preparing the Ground

Measuring and ordering are only the beginning. Before laying turf, preparation is key:

1. Clear the area – Remove old grass, weeds, rocks, and debris.
2. Level the ground – Ensure the surface is smooth and slopes slightly away from buildings for proper drainage.
3. Spread the underlay – Distribute the underlay evenly across the area at the calculated depth.
4. Compact and smooth – Lightly compact the soil with a roller or by walking over it to prevent future sinking.
5. Water the base – Lightly moisten the underlay before laying turf to help roots establish.

Step 6: Laying Your Turf

Once the measurements are complete and underlay prepared:

• Lay the turf rolls in a brick-like pattern, staggering the joints.
• Press the rolls firmly against each other to avoid gaps.
• Trim excess turf with a sharp knife.
• Water immediately after laying, soaking the turf and underlay.

Common Mistakes to Avoid

• Guessing measurements – Always measure, don’t estimate.
• Not ordering extra turf – Without a buffer, you risk running short.
• Ignoring underlay depth – Too shallow, and the turf struggles; too deep, and it becomes costly.
• Skipping soil preparation – Turf won’t thrive if laid over compacted, uneven, or poor-quality soil.

Why Work with Professionals

While DIY turf installation is possible, many homeowners prefer working with experts who can measure, prepare, and lay turf correctly the first time. Professional turf suppliers like Direct Turf not only provide high-quality turf but can also advise on underlay requirements, soil preparation, and aftercare to ensure your lawn thrives.

Final Thoughts

Measuring your garden for turf and calculating how much underlay you need may seem daunting, but with the right approach, it’s straightforward. Start by measuring the area accurately, calculate the turf rolls needed, then work out the underlay volume based on depth. Always allow for a little extra to cover cutting, shaping, and levelling.

By planning carefully and laying the right foundation, you’ll create a lush, healthy lawn that enhances the beauty and value of your home. And if in doubt, reach out to professionals like Direct Turf for expert guidance and reliable turf supply.