Rubber mulch, typically made from shredded, recycled tires, offers a durable alternative to organic materials for landscaping beds and playgrounds. This material is prized for its longevity, resistance to decomposition, and shock-absorbing properties, making it a popular choice for safety surfacing. To fully realize these benefits, a proper underlayment is necessary. The underlayment prevents the material from sinking into the soil, ensures proper water drainage, and keeps weeds from pushing through to the surface. Choosing the correct underlayment requires effective site preparation and selecting layers that address both weed control and long-term stability.
Essential Site Preparation
Preparation starts with completely removing all existing organic material, including grass, weeds, and old mulch or debris. Failure to remove pre-existing wood mulch, in particular, can lead to decomposition and moisture issues beneath the new surface.
Next, the area should be excavated to the required depth, which accounts for the thickness of the planned sub-base and the rubber mulch layer itself. This is especially important in playground applications where depth relates to safety standards. The entire surface must be leveled and graded to ensure that water drains away from structures, preventing pooling and moisture buildup. Finally, define the perimeter with a retaining border, such as plastic or timber edging, to contain the heavy rubber mulch and maintain a consistent depth.
Permeable Barriers for Weed Control
The most common material placed directly beneath the rubber mulch is a high-quality, permeable geotextile fabric, often referred to as landscape fabric. This barrier is designed to separate the rubber mulch from the native soil. A spunbond, non-woven fabric with a weight of at least 3.0 ounces is recommended for its superior durability and strength-to-weight ratio compared to thinner options.
The fabric works by physically blocking weed seeds from reaching the surface while allowing water and air to pass through to the ground below. When installing the fabric, overlap all seams by approximately four to six inches to prevent gaps where weeds could penetrate or the mulch could mix with the soil. Secure the barrier flat against the compacted ground using six-inch steel landscape staples placed along the edges and seams.
Sub-Base Options for Drainage and Stability
For installations requiring structural integrity, such as high-traffic walkways or playgrounds, a dedicated sub-base layer is necessary beneath the geotextile fabric. This layer provides a firm, stable foundation and significantly improves drainage characteristics. Compacted crushed stone, like decomposed granite or clean gravel, is a frequently used option due to its stability and excellent drainage capacity.
A structural base of compacted aggregate is typically installed in layers, often with a minimum depth of four inches to ensure maximum compaction and stability. This coarse material prevents the underlying soil from shifting or settling. Washed sand can also be used as a final leveling course over the crushed stone or directly on the soil in residential settings, providing a smooth surface for the landscape fabric and aiding in quick water percolation.