Retaining walls must
be constructed according to engineering specifications!
Height Of wall |
Post length |
Hole Depth |
Footing Diameter |
0.30m |
0.6m |
0.30m |
0.35m |
0.45m |
0.9m |
0.45m |
0.35m |
0.60m |
1.2m |
0.60m |
0.35m |
0.75m |
1.5m |
0.75m |
0.35m |
0.90m |
1.8m |
0.90m |
0.35m |
1.05m |
2.1m |
1.05m |
0.45m |
1.20m |
2.4m |
1.20m |
0.45m |
1.35m |
2.7m |
1.35m |
0.45m |
1.50m |
2.7m |
1.20m |
0.45m |
Note: 1.35m and 1.50m walls require backing
panels
The following direction describe the stages
of a common method of installation
- Set up a string line between two stakes positioned at
each end of the required wall.
- Dig the first two post holes to the depth and diameter
indicated above, and with centres 1.13m apart. (It is better
to dig the holes too deep and add more sand than to dig
too shallow and have to lift the post out to deepen the
hole)
- Place a post in the first hole, ensure it is at the correct
height, and add the concrete footing. Check the post is
vertical with a slight tilt towards the rear, as described
in step #7. When the first post is positioned correctly
adjust the string, using a string level, so that the height
above the ground indicates the top of the wall and that
it is aligned along the front and rear face of the wall.
- Place a post in the second hole, using a measiuring stick
to ensure it is the correct distrance from the first post.
Check that the top of the second post is level with the
top of the first post (just touching the string line), and
that the posts are aligned correctly.
- Dig two or three more post holes as in step #2, and place
the posts in the hole with the correct separation. Some
installers insert the bottom panel at this stage, but the
use of a measuring jig is generally better.
- Add concrete for footings. One part cement to four parts
sand is adequate for walls up to 0.90m high. higher walls
require arggregate (blue metal) for stronger footings.
- Lean post slightly (2°) towards the load side for
increased effectiveness, and ensure that the posts are in
a line and that the tops of the posts are at the correct
level.
- Install the panels, making sure the top panels are flush
with the top of each post. Brush the top of each panel to
prevent particals of sand or grit from creating a gap between
the panels. For a better finish insert thin wedges at the
rear of each panel to force them forwards befoire backfilling.
- An effective method, particularly if intending to pave
afterwards, is to keep the tops of footings below ground
level and a brick to support each panel. THis allows for
easier adjustment of the panel heights and gives room for
paving later.
- Continue and complete the wall. This can be done in a
number of stages if more convenient.
- Where the wall is used to retain a garden bed, the use
of plastic sheeting between the soil and the wall will help
to prevent seepage of water and assist in retention of moisture
in the soil.
Builders/Owners should check with their local councils for
the regulations governing retaining walls and obtain a licence
when required.
Download
engineering specification drawing. |