Earthworks – A Simplified Explanation – Part 3

Site & Earthworks - cut to fill average levels

Earthworks, what are they?

In this post, the second in the series, we explore more processes or site – earthworks items you may encounter.

Your contract quote should include all site – earthworks costs, however, some builders don’t finalise these costs until after works have commenced. Unlike other builders, Central Avenue Homes provides all costs for site – earthworks related items in our initial quote.

Service runs

On a rear strata lot, a house behind a house, all the services need to be connected to the rear house. They come from the supply location from the front house to the connection point of the rear home. These can include:-

  • Power,
  • Water,
  • Sewer,
  • Telephone,
  • Gas,
  • NBN, if included
  • or any other item specifically required for your site.

Generally, and if the site is managed well, the services are run in the same trench. Organising the service runs requires a great deal of coordination as all the trades need to be on site within a limited time. Building on a rear strata block requires even more coordination.


On smaller and rear strata blocks, piling is becoming more and more common. Piling can be required when:-

  • The block is subdivided
  • A new sewer line is created
  • To protect the old sewer line,
  • Difference in levels

Because, the Water Corporation may require an easement, piles must be installed. An easement is an area that is not allowed to be built on.

Sometimes piling is required when there is a difference in levels from one block to another. Retaining is not always an option. Piles, generally steel screw piles, are driven into the ground for support. They finish inside the footing they support, and a retaining wall is built on top of the ground.

An engineer designs a piling detail (a report) that the piling contractor follows. The piling detail ensures the piles are the correct size and installed to the correct depth.

Storm water disposal

Most shires (local authorities) now, require storm water disposal systems as part of their building permit conditions. Some shires require a report from a hydraulic engineer detailing the exact type, size and amount of stormwater disposal tanks, required for the block. Rainwater from the roof is calculated to work out the size or amount of stormwater disposal tanks. Storm water disposal can be either concrete tanks or more recent polypropylene modular systems. However, certain shires require connection to their own shire stormwater catchment system. And other shires require rainwater tanks as well as stormwater disposal.

Removal of excess soil

Digging the footings, drains (sewer) and stormwater systems creates a remarkable amount of excess soil that needs to be removed. On larger blocks, the earth worker digs a large hole in a clear space to dump some of the excess soil in. Because the soil doesn’t have to be taken away from site, this makes the earthworks cost cheaper for the client. However, on smaller lots, there isn’t  room to dig large holes, so it must be removed from site. Quite often there can be up to 20 cubic metres of excess soil that needs to be removed, because there is no room.

Limestone access track

In Perth there are a lot of sandy sites. Building at the rear of an existing home (rear strata or battle-axe lot) on a sandy site may require an access track. Because the lots are sandy, and difficult for trucks to drive on it’s necessary to place approximately 100mm of limestone on top of the access track. This in turn allows trades and suppliers to get their vehicles closer to the building site. The limestone track will compact the more it’s driven on.

No Surprises or additional unknown costs

With Central Avenue Homes, you are guaranteed:

  • All costs are provided upfront
  • There will be no unexpected or unknown costs.
  • The works are supervised by us as part of the building process.
  • All works are completed to Shire and Engineer requirements.


For a more specific idea of Site – earthworks for your block contact us at Central Avenue Homes.

Or call and speak to our in house designer 9456 3366 or email [email protected]

Posted by Lee Grainger

Check out our other blog posts in this series for more insights to site – earthworks:-

A simplified explanation of site – earthworks Part 1

A simplified explanation f site – earthworks Part 2

A simplified explanation of site – earthworks Part 4