Landscape fabric is commonly used in gardening and landscaping to manage weeds and separate materials. Homeowners often confuse whether this material is waterproof. Unlike materials designed to repel water, landscaping fabric is engineered to interact with moisture in a specific way. Understanding how water moves through this textile is fundamental to its effective use.
Material Structure and Water Permeability
Landscaping fabric is not waterproof; it is designed to be permeable, allowing water and air to pass through to the soil underneath. This permeability results from its construction, which falls into two categories: woven and non-woven. Both types are made from durable synthetic fibers like polypropylene or polyester.
Woven fabrics are produced by interlacing thin strips of material, creating a grid-like pattern. This construction offers high tensile strength and durability, making them suitable for high-traffic areas. Non-woven fabrics are made by bonding fibers using heat or chemicals, resulting in a flexible, felt-like mat.
Non-woven fabrics are often used for filtration and drainage applications, such as wrapping French drains, because they are typically highly permeable. Woven fabrics are preferred for long-term use under gravel or mulch due to their superior strength and resistance to tearing. The goal for both types is to manage water passage while preventing the movement of soil particles.
Defining the Core Functions of Landscape Fabric
The primary roles of landscape fabric in a garden setting are distinct from its water-handling properties, though they relate to its function as an underground barrier. One of the most common applications is weed suppression, which the fabric achieves by acting as a physical shield. By blocking sunlight from reaching the soil surface, the textile prevents the germination and growth of weed seeds beneath the fabric layer.
The fabric’s other function is material separation, acting as a clean boundary between different layers in the landscape. It is often placed between the native soil and decorative top dressings like gravel or mulch. This prevents the top material from sinking into the underlying soil, which maintains the integrity of the surface layer. This separation is useful in drainage systems, where the fabric allows water to filter through while keeping fine silt and soil particles from clogging the drainpipes.
Impact on Drainage and Soil Health
While initial permeability is a design feature, the long-term impact on water flow and soil health is a major consideration for users. For plants to thrive, the soil requires a constant exchange of water and air, which supports root growth and the soil’s microbial ecosystem. Landscape fabric, even when permeable, can impede this natural exchange over time.
As organic matter, dust, and fine silt accumulate on top of the fabric, they can clog the pores of the material, significantly reducing its permeability. This “clogging” effect leads to poor water infiltration, causing rainfall to run off the surface rather than soaking into the soil beneath. Reduced water penetration starves plant roots and can contribute to soil compaction, creating an unhealthy environment.
The restricted gas exchange due to the barrier can also inhibit the activity of beneficial soil microorganisms, which rely on air and moisture to cycle nutrients. When water cannot pass through easily, the soil can become waterlogged in some areas or excessively dry and cracked in others, stressing the plants. Therefore, while landscape fabric is not waterproof, its long-term use can effectively create a semi-impermeable layer that negatively impacts the balance of air, water, and nutrients essential for soil health.