Copyright Goodheart-Willcox Co., Inc. Chapter 14 Wall Systems 311 Trade Tip If necessary, use a small amount of sand and a rubber mallet to aid in leveling the block. Sprinkle the sand on the gravel base to aid in creating a level base. Then position the block on the sand and place a level on top to check for levelness over the length and width of the unit. If adjustments are needed, tap the high points of the block with a mallet until the unit is level. A mason line can also be used for elevation of the block to achieve alignment. 5. Install the drain tile behind either the first or sec- ond course. If the tile is to be run underground to a lower elevation away from the retaining wall, it is installed behind the first course where it is easier to hide it underground. Place pea gravel around and on top of the tile lying behind the retaining wall. Lay a fabric filter over pea gravel. The fabric filter aids in reducing silt from entering the tile. Backfill with base aggregate to the top edge of the first course and compact. Use 1/2″ or 3/4″ free- drainage aggregate 12″ directly behind the wall in 6″ layers and compact. Fill the void between units with aggregate and compact. 6. Install the next course. Stagger the vertical joints. Pull each unit forward until the lip aligns with the back edge of the course below. 7. Install the drain tile and pea gravel if a drain tile was not placed behind the first course. Cover the Goodheart-Willcox Publisher Figure 14-74. A sectional view of a hardscape retaining wall showing block and other materials that compose the wall. Filter fabric Gravel compacted Sand compacted Drain tile Filter fabric Pea gravel Geo grid mesh (if needed) Geo grid mesh Drainage aggregate Filter fabric Soil Soil Retaining wall block Cap block Geo grid mesh (if needed) pea gravel and place the fabric filter on top of the pea gravel. Fill the void between units with aggre- gate and compact. See Figure 14-74. 8. If a fabric filter was used, it should be laying against the back wall of the trench. Bring the remaining fabric forward and lay it over the top of the last regular course. The fabric stops the soil from migrating into the drainage aggregate. 9. Install backfill over the fabric filter or aggregate. Fill any remaining voids between the drainage aggregate and the embankment with backfill material (native soil). 10. Install the wall cap on the retaining wall. Certain caps may need to be cut using a masonry or diamond blade to ensure that the caps follow the contours of the wall. If a fabric filter was used, it should be placed between the block wall and finishing caps. Glue the caps down with a concrete masonry mastic intended for masonry products. Place the wall caps on the retaining wall. 11. Grade and contour the backfill to meet the exist- ing grade and terrain. Firmly compact the backfill soil and fill any voids and repeat compacting. Trade Tip To create partial units, use a masonry saw, splitter, or hammer and chisel to cut each unit to the desired shape and size.