Chapter 15 Hardscapes 411 Copyright Goodheart-Willcox Co., Inc. Thinking Green Permeable Hardscapes Installing a more permeable hardscape can reduce the impact a landscape design may have on the local environment. A more permeable landscape design will decrease stormwater runoff, reduce pollution entering our waterways, and increase the amount of water that enters groundwater reservoirs. The ground also serves as a filter to remove contaminants from the water. Materials and designs that can increase the permeability of a hardscape include decomposed granite, crushed stone, porous asphalt, pervious concrete, dry-laying the hardscape, and the use of permeable materials between pavers. • Decomposed granite and crushed stone form a hard compact surface that still allows water to seep through to the ground below. • Porous asphalt and pervious concrete both have interconnected spaces on the surface to allow water seepage. These materials may have restrictions for weight or the amount of traffic they can withstand. • Dry-laying a hardscape allows water to permeate the ground below. Dry- laid material is a hardscape that does not use concrete below and between the pavers. The materials are laid on a gravel bed with a geotextile and layer of sand below it. (Geotextiles are synthetic fabrics used as weed barriers, separations between materials, or to reinforce or protect a material.) A permeable material, such as moss, gravel, groundcover plants, or sand, is placed between the pavers or stones. Wet-laying is the installation of a hardscape with wet concrete below and between the pavers or stones. • Other types of permeable designs include a type of grid with open cells that can be planted with materials such as turfgrass or groundcover. The cells may also be filled with pea gravel or another type of aggregate. Permeable hardscapes may be subject to municipal restrictions and typically require a regular maintenance program. It is recommended that permeable landscapes only be installed on flat or minimally sloped areas. The amount or type of traffic may be restricted by a design and/or the materials used in its construction. Consider This 1. What are the major disadvantages of permeable hardscapes? 2. Is the cost of installing a permeable hardscape higher than that of traditional hardscapes? Explain your answer. 3. What types of recycled materials can be used to make a permeable landscape? Michael Dechev/Shutterstock.com Sergii Rudiuk/Shutterstock.com trairut noppakaew/Shutterstock.com Figure 15-17. Various types of gravel are available, adding color, texture, and permeable options to pathways and driveways. peasittichai/Shutterstock.com Thamma-touch/Shutterstock.com amperespy44/Shutterstock.com Joy Tasa/Shutterstock.com