New Product: Terralock

There is an old saying that “A good magician never reveals his secrets” and the same can be said among the design community. But we felt that this product was too good not to share with you. It’s a recently developed earth retaining system known as “Terralock” which is simple to use, cheap to buy, a truly sustainable product and best of all, it’s aesthetically pleasing.


Peter Harris, who is the Australian & New Zealand distributor of the product, introduced us to the Terralock system. At a time when so much emphasis is placed in sustainability and it seems that every product on the market has some kind of “green credentials”, it was refreshing to find a product that really is good for the environment.

Constructive Holdings Project - Main Road, QLD

The idea is simple. Terralock is not unlike sandbagging but it uses a man made geotechnical fabric instead of hessian material. The bags are then filled with a mixture of gravel, sand and compost in a special ratio to make them both stable and still act as a growing medium. It’s important that any organic matter is well composted so that the bags don’t subside. On remote or environmentally sensitive sites, existing site soil can also be reused along with gravel to reduce the impacts of transport and cartage.

Constructive Holdings Project

Once the site base is leveled and the bags are filled and tied, it’s simply a question of building them up like bricks. In between each layer sits a spiky plastic locking plate, which pierces into the bags and connects them. Spike on top of the locking plate then hold in place the next row of bags that are laid down. Irrigation can be placed between the bags as required depending on the type of plants you’re planning on using but in a lot of cases, natural seepage will do the trick.

Once the wall is built to its required height and angle, tube stock plants are either placed in between the layers or an incision is made in the bag and the plant is planted normally. About six plants per square metre gives full coverage quickly.

Constructive Holdings Residential Project

Then it’s a question of waiting and watching your retaining wall turn almost magically into a green wall.

The whole process is really easy.

E-GA project - Before retaining wall

It wasn’t hard to find the ideal project to try this product out – a young, environmentally aware couple who were building a new home and garden on the steep slopes of Kew. We were given a brief to turn the side of a hill into a series of functional outdoor spaces that still maintained a healthy balance of greenery amid hard surfaces. Our clients needed retaining walls to create terraces but didn’t want to be looking at walls of concrete everywhere. Another consideration for the design was an existing Peppercorn Tree that gave the garden an instant leafy appeal. We needed to be careful about encroaching on its root structure with retaining walls and offered Terralock as an ideal design solution.

Constructed Terralock retaining wall

Planting into the retaining wall

In this application, the Terralock wall had no engineering requirements, so the earthworks around the Peppercorn Tree were minimal. The permeable nature of this wall means that any roots that were severed during construction will have the ability to grow back through. We’re expecting that with three to six months, the planting will have completely covered the wall and it will look like a steeply ramped garden when in fact it is a structural retaining wall.

Three months after planting

Every council will have their own planning and building guidelines so check for permits and engineering requirements before you start. But as a guide, Peter from Terralock advises that no engineering is needed for vertical walls of up to one metre or for slopes of less than 60 degrees. If you do need engineering though, Terralock can provide it on request.

There is plenty of fly-by-night green technology about at the moment but Terralock looks like it will be here to stay.