Copyright Goodheart-Willcox Co., Inc. 310 Section 4 Construction Details Sizes of units for retaining walls include a 7″ × 18″ × 12″ straight face retaining block and 3″ × 13″ × 12″ reversible cap. Typically, the weight of the straight face blocks is 80 lb and the weight of the caps is 37 lb. Sizes, shapes, and weights vary among manufacturers. Retaining Wall Installation Before beginning construction, prepare a layout plan that considers the topography, drainage patterns, soil conditions, and local code restrictions. The proce- dure that follows is typical for retaining wall installation. PROCEDURE Installing a Retaining Wall 1. Excavate a trench. For walls up to 4′ high, one course is generally buried below grade. The trench should be at least 24″ wide, and deep enough to accommodate the amount of wall to be buried (usually at least one course plus the sand and gravel base). 2. After excavating, prepare the subbase. Roughly grade and level the loose soil and then compact it in the bottom of the trench. Then place 6″ of com- pactable base aggregate, usually 1/2″ to 3/4″ crushed stone, recycled concrete, or gravel in the bottom of the trench. Grade and level the base and then compact it. 3. If a fabric filter is to be used, install it on top of the base aggregate or stone and continue up the back side of the trench. The fabric helps to keep soil from migrating into the aggregate or crushed stone, which affects the drainage properties of the aggregate or stone. 4. Install the base course. Install the first course of units on the prepared base. Start at the lowest elevation of the trench. Level each unit as it is placed from side to side and front to back. Goodheart-Willcox Publisher Figure 14-72. Hardscape retaining blocks are made with a structural lip hangs approximately 3/4″ over the course below. The lip locks the course to the previous course so it does not move when backfill and soil are filled behind the wall. Lip Anchor Wall Systems, Inc. Figure 14-73. The tapered sides of these units make straight or curved walls possible for a variety of designs.