Start retaining wall at the lowest elevation
How to Build the Base Course (First Course)
Begin the base course at the lowest wall elevation. More information on retaining walls where the wall steps up a slope.
- Place all blocks with the raised front lip facing up and forward on the base material near the front of the base trench.
- Check and adjust each block for level and alignment as it is installed. Check the blocks for level frequently from side-to-side and front-to-back. Verify the proper position of all the retaining wall blocks by examining a string line across the back of the blocks or by sighting down the back of the raised front lip.
Install the first (base) course
Level and align the blocks
Backfill wall rock & infill soils
Compact the retaining wall
Install next course
Level and align the next course
backfill and compact
- Make minor adjustments by tapping the retaining wall blocks with a dead blow hammer or by placing up to 13 mm of coarse sand under the blocks.
- Irregularities in the base course become larger as the wall stacks up. Careful attention to a straight and level base course will ensure a quality finished wall.
Video: How to build the base course
Backfilling and Compaction
- Fill in the area in front of the blocks with on-site soils. This will keep the base course blocks from shifting while filling and compacting.
- Fill the hollow cores of the base course and 300 mm behind the block with wall rock to the height of the block.
Video: Backfilling and Compaction
- Use infill or approved on-site soils to backfill behind the wall rock in lifts of no more than 200 mm.
- Use a plate compactor to consolidate the wall rock directly behind the block then compact in a path parallel to the wall, working from the back of the block to the back of the excavated area with a minimum of 2 passes. More information on compacting your retaining wall.
- Check the base course for level and adjust as necessary.
- Every course after the first course requires compaction starting on the block.
Learn more on building a patterned retaining wall.
- Remove all excess material from the top surface of all blocks. This can be done when installing the next course of block, by sliding the blocks into place.
Stack Blocks with vertical seams offset
- If reinforcement is needed, go to reinforced walls to continue the installation process.
- Stack the next course of blocks so that the vertical seams are offset from the blocks below by at least 1/4 the length of the block.
- Check each block for level and alignment and make adjustments as needed.
- Fill the hollow cores and 300 mm behind the block with wall rock to the height of the block.
- Use infill or approved on site soils to backfill behind the wall rock in lifts of no more than 200 mm.
Video: How to build a gravity wall
- From the 2nd course and above use a plate compactor to compact directly on the blocks as well as the area behind the blocks. Compact in lifts of 200 mm or less.
- Repeating these steps, complete the wall to the desired height. On the last course, fill behind the blocks with organic soils in place of infill or approved on-site soils. This will assist in any plantings above the wall and also to direct water from running behind the blocks. More information on finishing your retaining wall.