Do I Need an Underlay for Artificial Grass

Benjamin7791flores 60918 Close Up View Of Vibrant Green Synthet F4cc1384 00b8 4b96 8449 B19901ed541c (1) (2)

Yes, in most cases, you absolutely need an underlay. It is the critical foundation that protects your investment, ensures safety and comfort, and significantly extends the life of your artificial grass by absorbing shock and preventing damage from the sub-base.

As a production manager, I oversee the creation of countless rolls of underlay. I see the material science that goes into every square meter, from the specific polymer density we engineer for shock absorption to the non-woven fibers we use for geotextiles. An artificial grass system is more than just the turf you see on top. The underlay is the unsung hero that dictates long-term performance. Without it, you’re placing the expensive turf’s backing directly onto an abrasive or uneven sub-base. This creates pressure points on the tuft stitches, accelerates wear, and leads to a firm, unforgiving surface. I’ve seen installations fail prematurely not because of the grass quality, but because of a poorly chosen or omitted underlay. It’s the engineering foundation that ensures the surface performs as intended for its entire lifespan.

A lush artificial grass lawn with a visible cross-section showing the underlay beneath

Choosing to install an underlay is the first step. The next is understanding that not all situations are the same. Your specific project—whether it’s a concrete balcony, a backyard play area, or a lawn for your pets—will determine exactly what you need.

Is Underlay Always Necessary for Artificial Grass?

It is non-negotiable for hard surfaces, children’s play areas, and for pet owners who want optimal drainage. While technically optional on a perfectly prepared aggregate base, skipping it severely compromises comfort, longevity, and the overall quality of the finish.

Installation Scenario Underlay Requirement Key Reason
Hard Surfaces (Concrete, Decking) Non-Negotiable Prevents abrasion, masks imperfections, adds shock absorption.
Children’s Play Areas / Schools Non-Negotiable Meets Critical Fall Height (CFH) safety standards.
Lawns for Pets Highly Recommended Aids urine drainage, prevents odor buildup, adds comfort.
Rooftop Gardens / Balconies Highly Recommended Enhances comfort, aids drainage, and reduces noise.
Perfect Aggregate Base Optional (But Recommended) Primarily for added comfort and long-term protection.

Why Specific Situations Demand Underlay

When you lay turf directly on concrete, you create direct friction that grinds down the turf’s backing. For children’s play areas, the discussion is about safety. We engineer shock pads with a specific cellular structure to meet standards like ASTM F1292, which is about absorbing kinetic energy to prevent serious injury.
A point I must emphasize is for pet owners. A key pain point is urine smell. A permeable underlay lifts the turf off the sub-base, creating an air gap that promotes drainage and airflow. This allows urine to wash through the system instead of getting trapped in the turf backing, significantly reducing the risk of persistent odors. It also provides a more comfortable, forgiving surface for your pets’ joints.

A happy dog playing on comfortable and safe artificial grass with underlay

The benefits in these key scenarios are not just about luxury; they are about safety, hygiene, and protecting your investment.

Which Type and Thickness of Underlay is Best?

The best underlay matches your primary use. Foam is a great all-rounder, shock pads are for safety, and thickness should be chosen based on the balance of comfort and function you need. Do not confuse a geotextile membrane with a cushioning underlay.

Underlay Type Primary Material Best For Thickness Range
Foam Underlay Closed-Cell Polyethylene (PE) General lawns, patios, pets 5mm – 12mm
Shock Pad Engineered Foam/Rubber Playgrounds, sports areas 20mm – 50mm+
Geotextile Membrane Non-Woven Polypropylene Soil/aggregate sub-bases N/A (Not for cushioning)

A Manufacturer’s Guide to Thickness

Choosing the right thickness is a frequent question from customers. It’s a balance between comfort, performance, and cost. From a manufacturing standpoint, here’s how to decide:

  • 5-8mm: This is an excellent choice for installations over hard surfaces like concrete or patios. It’s thick enough to smooth over minor imperfections and take the "hardness" out of the ground, providing a significant comfort boost without feeling overly spongy.
  • 10-12mm: This is the sweet spot for most domestic gardens, especially those with families or pets. It provides a lush, cushioned feel underfoot that mimics a high-quality natural lawn. It offers a great balance of comfort, performance, and value.
  • 20mm+ (Shock Pads): This category is specifically for safety applications. These are not chosen for general comfort; they are engineered and specified to meet a Critical Fall Height (CFH) rating for playgrounds under swings, slides, and climbing frames. Using this on a regular patio would be overkill and feel unnaturally bouncy.

A side-by-side comparison of different underlay thicknesses

The selection process is straightforward when you match the material’s purpose and thickness to your project’s primary need.

How Do You Install and Troubleshoot Underlay?

Proper installation involves laying the underlay flat, butting the edges tightly together, and securing the seams with strong tape. Most problems, like visible lines or poor drainage, come from incorrect installation, not a faulty product.

Common Problem Probable Cause Solution
Visible Seams Edges not butted tightly; weak tape. Use strong waterproof tape and ensure no overlap.
Spongy/Bouncy Feel Underlay too thick for the area; unstable sub-base. Choose appropriate thickness; ensure sub-base is compacted.
Poor Drainage/Odor Non-permeable underlay; adhesive blocking holes. Use a perforated underlay; use spot adhesive, not full coverage.

Key Installation and Troubleshooting Tips

As a manufacturer, I know that even the best product will fail if installed incorrectly. Here are the most critical points I share with installers:

Installation Basics

  1. Lay it Flat: Roll the underlay out over your prepared sub-base. Let it settle if possible.
  2. Cut to Fit: Use a sharp utility knife to trim the underlay to the perimeter of your lawn. I recommend leaving a small expansion gap of about 1/4 inch (5-10mm) at the edges.
  3. Join the Seams: This is the most critical step. Butt the edges of two pieces together so they touch perfectly without overlapping. Run a high-quality, waterproof cloth tape (like Duck/Gaffer tape) along the entire seam to create one continuous sheet. Do not use cheap packing tape.
  4. Secure if Needed: On concrete, use dabs of turf adhesive to stop the underlay from shifting. On an aggregate base, the weight of the grass and infill is usually sufficient.

Solving Problems

The most common "product failure" calls we get are actually installation issues. For example, if you see lines through your grass, it’s almost always because the underlay seams were overlapped instead of butted together. If you have drainage issues, check that your underlay is perforated and that you haven’t accidentally blocked the drainage holes with a solid layer of adhesive.

A DIY installer joining two pieces of foam underlay with waterproof tape

Taking the time to install the underlay correctly is a simple step that prevents 99% of future problems.

What Is the Real Cost of Artificial Grass Underlay?

A quality foam underlay typically costs between $1.50 to $3.50 per square foot. While this adds to the initial project budget, it is a small upfront cost that protects a much larger investment and prevents costly future repairs.

Underlay Type Typical Price Range (per sq. ft.) Value Proposition
Standard Foam (5-8mm) $1.50 – $2.50 Excellent value for basic comfort and surface smoothing.
Premium Foam (10-12mm) $2.50 – $3.50 Best investment for family and pet lawns for comfort/longevity.
Safety Shock Pad (20mm+) $4.00 – $7.00+ Non-negotiable safety investment for play areas.

An Investment, Not an Expense

Thinking about this from a production and asset management viewpoint, the artificial grass is the main asset, but the underlay is the insurance policy for that asset. The cost of a quality 10mm underlay might be 15-20% of the total material cost, but it can extend the satisfying, comfortable life of the system by 25-50%. Without it, you risk premature wear, which could mean replacing the entire lawn years earlier than expected. The small investment in a proper underlay system provides a stable, protective layer that absorbs stress, ensuring the surface remains even, comfortable, and intact for many more years.

Conclusion

Choosing the right underlay is not an expense; it is the single most important investment you can make in the foundation of your artificial lawn for lasting safety, hygiene, and performance.

Ready to build your perfect lawn on a solid foundation? My team and I are here to provide the technical guidance you need. Contact us today for a complimentary design consultation, a custom quote, or to request free samples tailored to your project’s specific requirements.