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CornerStone - Installation Instructions

The following are the basic steps involved in constructing a conventional (non-geogrid reinforced) CornerStone wall. These steps are to be used in conjunction with all relevant details provided in the Technical Information section.

For construction of reinforced walls, please consult the details provided in the Technical Information section.


Step 1 - Plan:
With your final design in hand, begin to establish the wall location and proposed grades. Locate all utilities and contact local utility companies before digging. Mark a line where the front of the wall will be placed, keeping in mind the 5/8" (16 mm) setback per course.

Step 2 - Excavate:
Excavate a trench down to the foundation grades specified in the design. The front of the trench should be 6" (150mm) from the planned face of the block. The trench should be a minimum of 30" (750mm) wide (front to back) and 14" (350mm) deep. This depth assumes one unit is buried (unit height of 8" [203mm]) plus the compacted granular base minimum depth of 6" (150mm). As wall height increases, depth of embedment also increases, normally about 10% of the wall height. Greater embedment depths may be required to account for slopes more than 3H:1V in front of the wall, scour protection in water applications, global stability, or as specified in the design. The rear 6" (150mm) of the trench is excavated to account for the drainage layer. Excavations should be conducted in accordance with local codes.

Step 3 - Verify Foundation Subgrade:
Once the foundation trench has been excavated to the specified elevations, the native foundation soil must be checked to ensure that it has the required allowable bearing capacity specified in the design.

Step 4 - Prepare the Compacted Granular Base:
Start the base at the lowest elevation of the wall. The base should be composed of well-graded, free-draining (less than 8% fines), angular granular material (5/8 minus or 3/4 minus crushed rock), and compacted to a minimum of 98% SPD. The minimum base thickness is 6" (150mm) or as required to reach competent founding soil. Geotextile might be required under the granular base. The minimum base dimensions are 24" (600mm) wide (front to back) and 6" (150mm) deep. The additional 6" (150mm) trench width allows for the placement of the drain.

Step 5 - Step the Base:
When the grade in front of the wall slopes up or down, the base must be stepped to compensate. Working out the stepped base as the wall steps up in elevation, the foundation steps must be located to ensure the minimum embedment is achieved. The height of each step is 8" (203mm), the height of 1 course. The 5/8" (16mm) offset must be accounted for at each step.

Step 6 - Place Filter Cloth:
Lay the approved filter fabric (geotextile) along the bottom of the rear of the trench and extend up the exposed excavation to the proposed wall height. Leave adequate material at the top to fold back towards the wall (completely containing the drainage material). Stake the filter cloth against the slope during construction.

Step 7 - Place the Drain:
Various options for drain placement may exist, depending on how the pipe is to be outlet (refer to Water Protection available in the Design Considerations section). The drain may be outlet through the wall face or connected to a positive outlet (sewer). The drainage system is extremely important and outlets must be planned prior to construction. In the case of connecting to a positive outlet, the drain should be placed at the lowest possible elevation and sloped at a minimum of 2%. At the rear of the base, allow the granular material to slope down on the sides towards the drain trench. In the 6" (150mm) area behind the base, place the approved drain tile (perforated drain with filter sock) on top of the filter cloth and minimal granular coverage.

Step 8 - Place the First Course:
Position a level string to mark location of the back of the first course (should be 12" [300mm] from the proposed wall face). Place the first course of blocks side-by-side (touching) on the granular base - unless your wall curves, then space the blocks slightly apart to allow for the 5/8" (16mm) setback. Ensure units are level front to back and left to right. Extra care should be taken at this stage as it is critical for accurate alignment. Complete the entire base course before beginning the second course.

Step 9 - Second & Additional Courses:
Sweep top of underlying course and stack next course in a running bond pattern so that middle of the unit is above the joint between adjacent blocks below (9" [225mm] offset). Continue stacking courses to a maximum of 3 courses (24" [600mm]) before backfilling.

Step 10 - Backfill Drainage Material:
A free-draining, 3/4" (19mm) clear stone drainage material is placed immediately behind the wall facing and compacted with a light manual tamper. The drainage layer must be a minimum of 12" (300mm) thick and protected from the native material by the filter cloth.

Step 11 - Continue Stacking & Backfilling:
Continue stacking units and backfilling as described in Steps 10 & 11 until the desired height is reached, based on the design.

Step 12 - Place Cap Units:
A layer of concrete adhesive must be applied to the top course in order to fix the cap units in place. Place the cap unit firmly on top of the adhesive, ensuring both surfaces are free of debris, and apply pressure to secure. Follow adhesive installation guidelines.

Step 13 - Encapsulate the Drainage Layer & Finish Grading:
Fold the excess filter fabric over the top of the drainage layer and extend up the back face of the coping unit. Ideally, place an impervious layer of soil on top of the filter fabric and compact manually, providing for the required grading and/or swales. For other treatments such as pavers, concrete, or asphalt, care must be taken to ensure that heavy compaction/paving equipment remains a minimum of 40" (1.0m) from the back of the cap unit. Slope the surface above and below the wall to ensure water will flow away from and not accumulate near the wall units.