Retaining Wall Construction Building A Block Retaining Wall

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Retaining Wall Construction Building A Block
Retaining Wall

• Developed by
• Dr. Teri Hamlin
• Georgia Department of Education

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Purpose

• To level a steep slope
• Enclose an area for a decorative garden
• Elevate Beds

A block retaining wall can dress up the
landscape.
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Equipment Needed

• Tools
• Chisel
• 3 lb. sledgehammer
• Torpedo level
• Line blocks
• Mason's line
• Line level
• Flat-pointed shovel
• Hand tamper
•  Materials     
• Retaining wall blocks
• Porous plastic landscape fabric
• Gravel (optional)

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AdvantagesConcrete Interlocking Blocks

• Most concrete blocks interlock and require no
  mortar.
• If you make mistakes or change your mind about
  the location or shape of your wall, just
  dismantle it and start over.

Each block has a lip that locks it to the
previous row.
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Uses

• Terraces with low walls
• Using a system of terraces, you can create a
  pleasant, stepped slope that is safer than a
  single, tall wall.

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How These Block Systems Work

• Mortarless systems have a lip on the bottom rear
  side to lock the blocks together and create a
  step effect
• When the cavity behind the wall is filled with
  soil, the blocks are pushed forward,
  strengthening the joints between the lips and the
  underlying blocks

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How many do I need?

• Determine the height and width of the wall. 
• Calculate the square footage of the wall by
  multiplying the estimated length by the estimated
  height (which should include the base course) of
  the wall.
• Example 25' L x 2' H 50 sq/ft.
• number of blocks you need depends on the pattern
  you choose and the square footage of the wall
  above grade.

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How many do I need?

• Number of blocks needed depends on the pattern
  you choose and the square footage of the wall
  above grade
• Example
• Each block covers approximately 1/3 of a sq/ft
  (.33), therefore, for 50 sq/ft you will need
  approximately 152 blocks. (50 divided by .33
  sq/ft per block)

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Getting Started

• When figuring how many blocks you'll need for
  your wall, remember that curves require more
  blocks than straight runs.

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How many blocks do I need for a curve?

• The number of blocks needed will depend on the
  style of block used and the size of the curve.
• The formula to calculate the number of blocks
  needed for a specific curve is
• (2 x 3.14 x radius of curve) divided by the width
  of block. 
• The radius needs to be measured in inches (number
  of feet x 12").
• Example One course of a 10' diameter tree ring.
  Radius is 5' x 12" 60".

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Getting Started

• To accurately cut a block, score a line around it
  with a 3 1/2" 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.

Use a brick chisel to score and cut your block.
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Dig the Trench

• Measure out your prospective wall, using stakes
  and string to mark off the key points, or use a
  garden hose to mark off its perimeter.
• Starting at the lowest point, use a flat-pointed
  shovel to dig a trench for the foundation course.
  The dimensions of the trench will vary depending
  on the size of your block, but the foundation
  course should be below ground level.
• Tamp the trench with a hand tamper to compact the
  underlying soil.

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Sloping Property

• If your property slopes, you may have to dig your
  foundation trench in a series of steps equal to
  the height of the blocks.
• 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.

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Lay the Courses

• Set the first block in place.
• Check for level. If the block isn't level, tap it
  with the butt end of your sledgehammer to adjust
  it.

Check the level of the foundation course before
you start the second course.
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Lay the Courses

• If your property is relatively flat, continue
  laying the foundation course, making sure that
  all blocks are level with each other and below
  ground.
• If not, use the stepped approach mentioned in
  previous slide.

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Lay the Courses

• After the entire foundation course is installed,
  set one block in position at each end of the
  foundation course.
• The lip of each block should fit against the back
  of the foundation course block.
• 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.

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Lay the Courses

• Cut one block in half for the start of the second
  course.
• This will ensure that the first and second
  courses are staggered.
• Set the rest of the second course blocks in place
  and then fill the trench around the foundation
  course with soil.
• Continue placing the blocks, making sure each
  course is staggered over the previous one.

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Fill the Cavity

• To prevent the soil from seeping through the
  spaces between the blocks, line the cavity behind
  the wall with porous, plastic landscape fabric.

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Fill the Cavity

• Start at the base of the cavity and unroll the
  fabric until it overlaps the top course of block.
  
• Cut the fabric and continue along the length of
  the wall until the entire cavity is lined.

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Completing the Job

• Fill the cavity.
• If the wall is 2 1/2' or higher, fill the area
  closest to the block with gravel. You should have
  gravel to a width of about 6" from the block. The
  rest of the cavity can be filled with soil. This
  will facilitate drainage.
• Trim the excess landscape fabric. You can top off
  the terraces with decorative stone or mulch.