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Where do you start with building a custom home?

A pre-build feasibility is the place to start when building a custom home. This calculates the cost to prepare your land, as well as the cost of design and construction.

So you’ve decided to build a custom-designed home that’s a perfect fit for you and your family. You know what you need, and also what you like (maybe you even have a Pinterest board full of inspirations). Great! Now, what’s the first step in turning your home dreams into reality?

The first thing you need is a pre-build feasibility. This is an assessment of the costs associated with preparing a particular block for construction. It will also give you a ballpark figure for the costs of designing and constructing your dream home.

“The pre-build feasibility is when you get a ballpark figure for how much it’s going to cost to build your custom home.”

You can do a pre-build feasibility for the land you’ve already bought, or for the land you’re considering, as part of your pre-purchase research.

A pre-build feasibility is the first time your dream-home ideas are professionally assessed in the context of a real building site, and the first time figures can be attached to your project.

You might decide to contact a few different companies for a pre-build feasibility. Different businesses have different approaches. At Algin we ensure both an architect and builder are involved, so we can provide professional advice for both design and construction.

Why do I need a pre-build feasibility?

The pre-build feasibility is a critical step in determining the budget for your custom build. During this assessment, the site and external costs are estimated – things like excavation, tree removal, and service connection. These costs are mostly fixed, no matter what kind of house you ultimately build on the site.

After the site and external costs are calculated, the builder and architect can provide you with an idea of the size and complexity of the home you can achieve within your budget, and give you examples of similar designs.

Site and external costs are one of the four components of a home-build budget, alongside design fees, construction costs, and the cost of design consultants. For a deep dive into these four cost components, see our blog post How Much Does it Cost to Build a House?

What happens on a pre-build feasibility?

Listed below are the things that we at Align look at when we do a pre-build feasibility assessment – we call it a Project Possibilities meeting.


The steeper the site, the more expensive it will be to build on it. We assess the slope, but also look at the potential to build along with a contour in the land to save on the cost of earthworks.

Rough budget: $10,000 per metre of fall over the house site.


It’s obviously preferable to keep established trees wherever possible, but if there is a danger to the house, or you need to let in sunlight, they need to be removed. The danger posed by trees depends on the age and species of tree, some trees are more likely to fall or burn than others.

The cost of getting the labour and equipment to the site is a large part of the cost. It will cost less per tree to clear a number of trees than just one or two. The size of the tree can also affect the cost of removal. A tree from 4m to 10m high could range from $500 to $1200 (to give you an idea, power poles are usually 10m to 12m high). A tree 10m to 30m high could range from $1200 to $5000. Bushy trees cost more because they require more work to clean up for felling.

The cheapest way to remove trees is to fell them with a chainsaw and clear them with an excavator before the building begins. If they can’t be removed in this way, a tree climber with an elevated work platform will be required, the day rate for which is about $2500.

It’s important to think about which trees you want to remove before you build. It costs about three times more to remove a tree once the home is built, as the tree removalists need to work around the building.

Rough budget: $500-5000 per tree depending on how many must be cleared.


A pre-build feasibility will look at the best road access point for the house and the cost of excavating and surfacing a road.

Rough budget: $20 to $25 per square metre for driveway construction with 200mm thick gravel; the price per metre decreases over a long distance. A plain concrete drive costs around $120 to $170 per square metre.


This won’t be a big issue if you’re building on a serviced block, but one of the biggest costs of building on a bush block is the cost of connecting services. It’s important to determine right from the start which services are available at the block and where they can be accessed. If the services are located a long distance from the block, it may well be worth looking at other options, such as going off the grid. For example, it can cost $30,000 to dig in a power connection over a long distance, but it’s only about $30,000 for a good, off-grid solar-power system.

If your block is unserviced, you may need to budget for:

  • Water tanks
  • Access road
  • Wastewater system
  • Stormwater system
  • Fire tank
  • Power connection
  • NBN wire connection

Rough budget: $50,000 for connecting services to an unserviced block.

“It can cost $30,000 to dig in a power connection over a long distance, but it’s only about $30,000 for a good solar-power system."


If you would like extra buildings on the site, such as sheds, garages, or workshops, these should be taken into account during the pre-build feasibility.

Rough budget: A 12m x 7m prefabricated shed, including shed supply, concrete slab, erection, power connection, and plumbing downpipes is about $40,000.


The amount and type of fencing must be considered, as well as any gates or entry structures that may be required.

Rough budget: An 1800mm high, double-sided colour fence on a concrete plinth costs around $150 per linear metre.

Ideal Location

On a larger block, there may be a few options for sitting, and orienting, the home. A pre-build feasibility will consider the options, taking into account factors such as views, the direction of the sun, other buildings on the site, the road access, wind strength and direction, boundaries, neighbours, and privacy.

Soil Type

Soil type has an enormous impact on the concrete footings of a home. Clay soils tend to move, expanding when wet and shrinking or cracking when dry, which requires design adjustments. However, some foundations can be poured directly onto sandy soils, which is a lot less expensive.


The landscaping plans for the site must be taken into account, whether they will be initiated at the time of the home construction, or handled later.

Planning Overlays

The architect will assess the planning overlays for the site that will impact the design. These include regulatory restrictions such as zoning, bushfire attack level, and allowable wastewater system designs. The architect will be able to give a good assessment of the various regulatory restrictions that will apply to the particular site.

Doing the sums to build a custom home

Once the builder and architect have assessed the site and external costs, they can provide a figure and calculate the budget available for your design and build costs.

For example, a pre-build feasibility might determine that you are looking at $90,000 in site and external costs to develop your block. if you have a home-build budget of $600,000, you know you’ll have $510,000 left for design, construction, and consultants costs.

The architect and builder will give you an idea of the design consultants you’ll need on the project, for example, a site surveyor, bushfire assessor, or building surveyor, and the budget to allocate for this.

They’ll also discuss the size of the home you’re planning to build, such as the number of bedrooms, bathrooms, and living spaces, and will be able to advise you on the complexity of the design you'll be able to achieve within your budget. They’ll calculate an initial square metre rate for your project. Many factors feed into the square-metre rate equation, which we’ve looked at in detail in the blog post: How to calculate the square-metre rate to build your home.

After the feasibility

Once you have an idea of the budget available for design and construction, you can begin to research home designs in your ballpark. At Align, we look over similar projects featured on our website, which range in budget from under $300,000 to over $2 million.

The next step is for the architect and builder to put together a design proposal with a fixed fee. The architect will double-check the numbers and come back to clients with a fixed fee, it’s unusual for this to differ from the design fee quoted at the project feasibility stage.

Find out more about the steps in designing your dream home in our 7 Steps to Design + Build Your Dream Home Guide.

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