Definition of Terms:

  • core-fill:
    Concrete blocks are made with holes in them so the holes can be filled with masonry material (cement, crushed rock, foam, etc) so as to reinforce the block and create a solid structure.

  • excavate:
    To dig or shovel out the predetermined area for the leveling pad.

  • leveling pad:
    The leveling pad is the area of crushed rock that forms the base for the first course or bottom row of blocks.

  • lines:
    Lines are made of cord, rope, wire, string or even chalk to mark the ground or surface of the area to be excavated or built around.

  • grade:
    The grade is the degree of rise or descent of a sloping surface.

  • course:
    In architecture, a course is a continuous range of concrete blocks, stones or bricks on the face or roof of a building or wall creating a progressive pattern.

  • wall batter:
    Wall batter indicates a gentle backward slope increasing the depth thereby increasing the strength or stability of the wall.

  • range of action:
    The limits of possible variations of amount or degree of movement in a particular direction.


Materials Required:

  • gloves
  • line (string or wire)
  • shovel
  • hoe or rake
  • 3 ½" brick chisel
  • 3 lb. sledgehammer
  • 2-3 6' metal pipes or stakes
  • level
  • fine leveling sand
  • landscape fabric
  • exterior grade concrete adhesive


Please contact us for assistance in determining the quantity of block, crushed rock backfill or leveling sand necessary for your project.

Bring in the measurements of your project. Our experienced staff is available to assist you.

Installation Instructions

Core-fill, Gravity Retaining Wall - 3' Tall

Installation Notes:

Retaining wall installation is real quick and easy if you take care in correctly installing the first course.

The first course is the lowest row of blocks and likely won't show in your final project. However, maintaining a level first course is very important for a solid finished structure.

Each block needs to be set level by itself and level with the adjacent block. Once the base course is set, the rest of the wall goes together easily and quickly.

Core fill systems are stabilized by adding ½" crushed rock to inside of the block. The crushed rock works its way thru the wall and ties the whole wall together. It is recommended when filling each core to leave about a 1"-1/2" below the top of block, to ensure proper locking of material between courses. When you add the crushed concrete to the course above it falls into this additional space and locks that blocks together. The crushed rock is usually available at your local landscape supply distributor.

The taller the wall is being built, the more crushed rock will be required in the base. Please call us for specific recommendations or for calculating the necessary block required for your project.

Our experienced staff is available to assist you.


1) Excavate to the lines and grades required.
Dig a trench deep and wide enough to accommodate 2" to 4" of compactable, drainable leveling base and still be able to bury the bottom block. (For example: 4" of ½" crushed rock or recycled concrete depth + the 8" Cuesta wall block depth means your trench should be 10" to 12" deep.)

Note: If your property slopes, you may have to dig your foundation trench in a series of steps equal to the height of the blocks. Then, as you continue with construction, build up the lower sections with block until the stepped areas accept successive courses of blocks in a level and seamless wall.

2) Leveling pad in the trench bottom should be cut to a depth of 4".
To insure it is level, establish grades in the leveling pad by setting the tops of two 6' to 8' long "grade pipes" at each end of the wall. If the wall is long, a third pipe can be used in the center.

3) Mark the proper elevation.
To maintain the proper depth of the trench and keep it level while digging, tie a string or wire tightly between each "grade pipe". Use a plumb line to assist in determining the necessary depth. The string will also assist when leveling the ½" crushed rock base.

4) Line the trench with landscape fabric.
To prevent the soil from seeping through the spaces between the blocks, line the cavity with porous landscape fabric.

Leveling Pad / Base Preparation:

1) Spread leveling sand on the landscape fabric in the trench.
Use a rake or hoe to evenly distribute the sand to assist in leveling the crushed rock.

2) Distribute the ½" crushed rock in the trench.
Use a rake or hoe to evenly distribute the crushed rock between the poles in the trench to a depth of 4".

3) Level the pad.
The "grade pipes" and plumb line initially used for digging the trench are used again to insure the crushed rock in the bottom of the trench is level for the entire pad area. Use the string and plumb line to assist in leveling the ½" crushed rock along the entire length of the wall. (Another method of establishing the grade of the pad us to use a grade rod and transit or a laser level.)

4) Compact the ½" crushed rock.
Compact the crushed rock firmly so that it provides a level, drainable surface on which to place the first course of Cuesta block. A plate vibrating compactor may be used if the size of the project is extensive.

Wall Block Installation:

1) Start the wall at a fixed point.
Wall construction should start at a fixed point such as a building wall, 90° corner, or at the lowest elevation of the wall.

2) Place the first course of Cuesta on the base-leveling pad.
Repeatedly check the base course to ensure that each block is level from side to side and front to back and aligned perfectly with the neighboring block. Units must be in full contact with the base-leveling pad.

3) Carefully fill the unit cores.
Fill the unit cores and between the units, if working with curved walls, with core-fill material, (½" crushed rock is recommended). This technique helps lock the base block in place and maintain alignment. It is advised to fill the core just below 1" of the top of the block. This ensures a more secure interlocking of crushed concrete when you fill in the course above.

4) Re-check to be sure the first course is level.
Before backfilling, check to be sure the first course is level and the core fill material is packed tight. The top of the first course should be approximately equal to or below ground level.

Tip: After the entire foundation course is installed, set one block in position at each end on top of the foundation course. Use a pair of line blocks and a line level to make sure that the first and last blocks are level with each other. If they are not, adjust the retaining wall blocks until the foundation course is completely level.


1) Place core fill material behind Cuesta units.
The core fill material should extend a minimum of 8" to 12" behind wall. This allows free drainage of water, which reduces the pressures applied to the backside of the wall. Taller walls require more back fill.

2) Sweep excess material from top of units.
Once the surface is swept clear of any core fill material, begin to install the next course. A gas powered leaf blower works well for this step.

Successive Courses:

1) Start the second course.
Cut one block in half for the start of the second course. This will ensure that the first and second courses are staggered.

2) A ½" set back is recommended for each successive course.
Between courses, it is recommended to allow a minimum of a ½" set back, thus creating "wall batter" which anchors the wall into the slope creating better stability and drainage. Set the rest of the second course blocks in place and then fill the trench around the foundation course with soil.

3) Back fill after each course.
When each course is completely unit filled, back fill and compact behind the wall in 8" lifts before the installation of the next course.

4) Check alignment after each course.
Each course requires that the block be placed side-by-side and aligned perfectly. To help with alignment, use a string along the backside of the block.

5) Repeat these steps with each course.
As you repeat these steps, also check the level of blocks to the string guide.

Finishing the Top:

1) Installing the top row.
When installing the top row, turn the block over to create a flat surface. This is so you can adhere the cap to the flush surface of the top row of block. Use an exterior grade concrete adhesive to adhere the cap to the top wall block.

2) Backfill behind the wall.
Backfill behind the wall and compact to finished grade.

General Installation Tips:

• Gather all necessary materials and tools before beginning your project.

• To maximize efficiency, coordinate a plan of placing your work materials within a reasonable distance from the project to reduce unnecessary trips and expending extra time and energy. Keep in mind, when the blocks are delivered, do not have the pallets set on your driveway because they are extremely heavy and can cause damage.

• To accurately cut a block, score a line around it with a 3 ½" brick chisel and a 3 lb. sledgehammer. Place the cutting edge of the chisel in the center of the score line and strike the chisel sharply with the sledgehammer.

• After the first course is placed, two or three courses may be set in place before the core fill is added.

• Backfill materials should be installed in 8" lifts and compacted tightly for best drainage and stability.

• When building two-tiered walls, keep in mind, the "range of action" is twice the height of the bottom wall. This means, if the lower wall is 2' tall, the upper wall should be built 4' behind the lower wall.

•Before starting your project, check with local building codes as they can vary. Alleviate unpleasant surprises later.

For more information or further installation instructions on any of our wall systems, please contact us.

These instructions are provided as a service from St. Vrain Block. The information is intended to simplify your retaining wall building project. Since local regulations vary, St. Vrain Block assumes no liability for omissions, errors or the outcome of any project. Always exercise reasonable caution, follow current codes and regulations that may apply, and if in doubt about any procedure, consult with St. Vrain Block or another licensed professional.

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Installation Tips

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Glossary of Terms

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