The cut and fill method of construction is very popular for sloping building sites. It involves cutting back into a hillside and moving the soil to the lower side of the site to create a level building site. A retaining wall is then required to hold back the earth.
Problem wall
Don recently looked at a retaining wall that had cracked and needed replacing. The cost of this work would run to many thousands of dollars. The wall was made of brick and the backfill consisted of a clay fill with rubber tyres buried into it.
The problems seen on this site bring up matters you should consider before building a retaining wall. If the wall is correctly built from the beginning it will save a lot of time and money in the long run.
Check list
It is vital that you use the services of a structural engineer if you’re considering building a wall over one metre (3′) tall (that is if it is higher than you can step over). The engineer will consider the following points. These points can be used when appraising a block of land or an existing retaining wall.
Ascertain whether the site has been levelled by the cut and fill method.
Look at the type of soil or filling material behind the wall. Clay expands in the wet and shrinks during dry periods. If not properly handled this will lead to cracking in construction work.
Include weep holes at the base of a retaining wall to allow any excess water to escape. Lack of weep holes and drainage will lead to cracking and deterioration of existing retaining walls.
Strength of wall needed. A gentle arc shape will give great strength to a retaining wall.
Further information
Check with your local council for any building restrictions and whether you need council permission to build the wall. Contact a structural engineer for walls over one metre (3′) tall.
