When looking at the cost of a timber retaining wall, make sure you consider what type of timber is best to use for the renovation project.

For those who don’t mind a retaining wall lasting less than 40 years, the following looks at the best timbers available, according to Home Improvement Pages:

• Treated hardwood sleepers last between 7-10 years.
• Creosote-treated railway sleepers can last for 100 years.
• HR5-treated pine sleepers can last for 20 years.
• Treated pine logs have an estimated lifespan of 7-10 years.

The weather and soil conditions in the local area can affect the lifespan of the timber, but a timber retaining wall can be free of maintenance for five years or longer.

The cost of a timber retaining wall will depend on whether the timber is plain hardwood, softwood or treated. Split logs, timber slabs and the thickness of the timber also affect the overall price. Here are some pricing examples of timber retaining walls:

• CCA-treated pine sleepers – $15-20 for a 200 x 50 mm timber with a length of 2.4 m.
• Treated pine logs – $35 for a diameter of 150 mm and a length of 2.4 m.
• CCA-treated hardwood sleepers – $25 for a 200 x 50 mm and 2.4 m-long timber.
• Used railway sleepers – $75 depending on availability.

If undertaking a DIY renovation, the total cost of the retaining wall will be included in the price of the timber. Fixing materials and concrete should also be accounted for.

When building a timber retaining wall that’s more than a metre high, obtain council approval and a building permit by hiring a professional to do the job. This will cost about $150-300 per square metre.