Yes, lateral force on a wall would produce tensile stress on one side of the wall and compression stress on the other.  Concrete is very strong in compression but very weak in tension.  To compensate for the weakness, steel is added to the concrete.

Steel Reinforcement

The amount and placement of the steel reinforcements depends on the magnitude of the load and other factors.  However, there are some guidelines that we can use to preliminarily size and place steel in walls we propose.

But first, we need to know something about reinforcing steel or rebar.  It is mild, 60 grade (Minimum yield strength of 60,000 psi) billet steel, conforming to ASTM615.  You can see that it is ribbed (deformed) for good adhesion.  It is available in a range of sizes indicated by numbers that represent the eighths of an inch of diameter.  For example, the smallest rebar is #3 or 3/8" diameter.  For most landscape applications #3 and  #4 will be specified but very large diameters are available too.  You can see in the image that rebar rusts unless it is specified with galvanized or teflon coating.  The small amount shown in the image would be acceptable but the steel should be generally free of oils and rust.

Rebar is placed vertically and horizontally within cast-in-place elements.  It is held at least 2 inches from the surfaces of above ground, wall edges and at least 3" from below ground concrete surfaces.  This is to reduce the rusting of concrete inside the concrete that occurs when water migrates into the concrete.

 

Rebar Requirements for Free-Standing Walls and Retaining Walls

The tables below are provided as examples only.  If outside of this class, you need to specify rebar for walls, acquire engineered details from your local planning agency or consult an engineer.   The tables apply to concrete block walls but can be used for cast-in-place walls also.

Free Standing Walls with 6" or 8" Concrete Block
A pilaster is a structural column and serves the same purpose as a fence post.

Wall Height

Pilaster spacing

6 ft

12' - 0"  o.c.

5 ft

18' - 0" o.c.

4 ft

24' - 0" o.c.

 

Wall Height

Footing width

Vertical Reinforcement

6 ft

18"

#3  @ 32" o.c.

5 ft

15"`

#3 @ 48" o.c.

4 ft

12"

#3 @ 48" o.c.

3 ft

12" 

 ---

Specify 2 - #3 bar in wall bond beam (the top, horizontal course of block)- tie wall to pilaster.  Use 4 - #3 or 2 - #4 vertical bars in pilasters. Pilaster footing shall be 30" deep (or below frost line).

Retaining Walls with 6", 8" or 12" Concrete Blocks  (Uniform Load)

Wall Height

Block Size

Footing

Vertical Reinforcement

2 ft

8"

1' -11"

#3 @ 48" o.c.

3 ft

8"

2' - 6"

#3 @ 24" o.c.

4 ft

8"

3' - 0"

#4 @ 24" o.c.

5 ft

8"

3' - 8"

#4 @ 16" o.c.

Retaining Wall with Concrete Blocks   (Uniform Load)

Wall Height   

Block Size

Footing width

Vertical Reinforcement

Wall Footing Connection

Footing Reinforcement

3 ft

   6"

1' - 10" 

#3 @ 24" o.c.  

----

 #3 @ 48" o.c.

4 ft

   8"

2' - 6"      

#4 @ 32" o.c.  

----

 #4 @ 48" o.c.

5 ft

   8"

3' - 0"  

#4 @ 16" o.c. 

----

#4 @ 32" o.c.

6 ft

  12"

3' - 8" 

#4 @ 16" o.c.

#4 @ 24" o.c.

#4 @ 24" o.c.

7 ft

  12"

4' - 6"  

#4 @ 16" o.c.

#4 @ 16" o.c.

#4 @ 16" o.c.

8 ft

  12"

5' - 3"

#4 @ 16" o.c

#5 @ 16" o.c.

#5 @ 16" o.c.

Fill all cells with grout
Place 2- #4 bar in bond beam and 2-#4 bar near bottom of wall but above footing