Soil Matrix

SOILMatrix is a planting medium made of lightweight, ceramic material produced by expanding and vitrifying select shales, clays and slates in a rotary kiln. The process produces a high quality ceramic aggregate that is structurally strong, physically stable, durable, environmentally inert, light in weight, and highly insulative. It is a non-toxic, absorptive aggregate that is dimensionally stable and will not degrade over time. With a weight of about 50% of the weight of natural planting media, SOILMatrix contributes to sustainable development by conserving energy, reducing trucking requirements and minimizing the impact on structures. The use of this environmentally friendly ceramic material in greenroof design helps address important issues such as managing storm water runoff, improving water quality, reducing urban heat, conserving energy, lowering dead load and increasing green space.


SOILMatrix has a long history of success in horticultural applications all over the world. It is marketed under various trade names and has established itself as the standard for creating planting media for rooftop gardens.

Greenroof Planting Media


One of the most important components to both extensive and intensive greenroof systems is a quality planting medium. Because of the complex nature of greenroof construction and the difficulties of access after completion, the planting media must be able to support and sustain plants for the duration of the intended life span of the roof. A well-designed planting medium will have the following physical characteristics:

  • Be free of silts and clays that could clog the filter fabric;
  • Have permanent internal aeration even after several years of consolidation;
  • Insure adequate drainage;
  • Insure stable root support;
  • Not degrade, breakdown or shrink in volume over time.

SOILMatrix is the environmentally friendly answer that provides a long-term solution to the above complex design requirements. Besides exceeding all the requirements of an ideal planting medium, SOILMatrix provides additional important benefits. Its reduced weight can often accommodate structural design requirements; yet it is heavy enough to avoid loss caused by excessive wind or water. Its angular, stable and porous ceramic nature ensures an adequate supply of air to enable plants to be established quickly and develop healthy root systems. Ample aeration increases the insulative properties of the planting media and helps reduce energy consumption as well as lessen the urban heat island effect. Overall project costs are often reduced because SOILMatrix can also serve as the drainage portion of the greenroof system. When used for storm water management, the porous planting medium allows rain water to readily penetrate the soil surface. This reduces runoff and allows pollutants to be naturally filtered and remediated thereby improving water quality.

SOILMatrix: A comparison to other aggregates

Natural sand and soil are heavy. They frequently require that structural modifications be made to the project’s design. Native soils have silts and clays that may clog the filter materials or drainage layers and reduce effectiveness. The physical properties of natural volcanic aggregates vary widely with source and location. Natural materials may degrade and compact over time, and require additions to or replacement of planting media. Some horticultural products used in greenhouses and container planting, such as vermiculite and perlite, are extremely light in weight and do not offer adequate anchorage and support for larger plants. In exterior applications vermiculite and perlite often float to the top of the planting media where they can be carried away by wind or water.

LEED™ Benefits

The Leadership in Energy and Environmental Design (LEED) system was designed by the United States Green Building Council (USGBC) to evaluate the influence of building design and construction on the environment. SoilMatrix is an environmentally friendly, lightweight, ceramic product that saves material, labor and transportation cost. It also improves the functionability and service life when used in greenroofs and other planting media. These benefits support sustainable development and contribute to designs becoming LEED certified. For more detailed information on LEED, see ESCSI Publication # 7700.

SOILMatrix: The Versatile Planting Medium

Designers can count on SOILMatrix to be predictable, stable and highly dependable for the duration of the greenroof. The planting media mixture will vary depending on the climate region, application, aggregate and types of plantings specified. For optimal results it is essential to consult with the SOILMatrix supplier during the design phase of the project.