Chapter 15 Hardscapes 417 Copyright Goodheart-Willcox Co., Inc. Marking the Area After the necessary approval is given, the installer care- fully measures and marks the areas where the hardscape will be installed. Straight and curved lines may be marked with chalk or spray paint or by shoveling along the border. String attached to stakes may also be used to mark straight lines. See Figure 15-24. This is also the time to have utility lines marked if they have not been marked or the markings are no longer intact. These markings are used as guidelines for installation. They will also give the client a better idea of where the hardscape will be installed. Once the area has been measured and marked, the installer identifi es a bench- mark to which all measurements are compared. The benchmark is usually the highest point of the area, Figure 15-25. Setting the Final Grade A string level, rotary transit, or digital pole level can be used to develop the fi nal grade (slope). These devices use the established bench- mark as the base dimension. The installer calculates the total depth of the materials being installed to determine how deep the ground should be excavated. The total depth of the layers is then subtracted from the benchmark to identify the point to which the ground should be excavated. To maintain a stable base, the area should not be exca- vated deeper than necessary and no more than 1′ around the perim- eter. The backfi ll is set aside and used to fi ll in around the fi nished area. Subsurface Preparation One of the key elements of hardscape construction is adequate compaction of the subsurface (the area or layers below the fi nal surface), Figure 15-26. Proper compaction will ensure that weather extremes, such as freezing, thawing, heavy rainfall, and severe drought, will not cause the surface to buckle or shift. The standard subsurface depth for walks and patios is 4″, 6″ to 8″ for driveways, and 12″ for streets. A typical subsurface profi le for a hardscape, from the lowest layer to the uppermost layer, is as follows: • Drainage pipe (in some applications). • Large, porous aggregate. • Smaller aggregate, such as sand. • The hardscape material with sand or other small aggregate fi lling open spaces. Pro Tip Polypropylene panels are gaining popularity as an alternative to compacted aggregate, especially in areas subject to damage from freezing and thawing and those with limited access. The polypropylene panel is laid on the compacted subsoil before the hardscape materials are installed. Using this material may reduce excavation and material costs. Bildagentur Zoonar GmbH/Shutterstock.com Figure 15-24. Work areas within a site can be identified using string, marking paint, and/or flagging. Richard Thornton/Shutterstock.com Wave_Movies/Shutterstock.com CuteSalika/Shutterstock.com Figure 15-25. A benchmark can be identified on a site as the starting point for elevation calculations. The benchmark should be located out of the work area.