What Fixed Price Really Means Macarthur Building Contracts
What "Fixed Price" Really Means, and How to Make Sure Yours Is
A plain guide before you sign a building contract, from a Macarthur builder who has watched where they go wrong.
If you have built or renovated before, you already know the feeling.
You signed a contract that said fixed price at the top. You did your homework, or thought you did. You compared quotes. You picked the builder who seemed the most reasonable. Then the bills started to climb. A bit here for something they "found." A bit there for a choice you did not know you still had to make. A variation for site works nobody mentioned when you signed. By the end, the home cost far more than the number you signed, and there was nothing you could do about it, because every extra charge was technically allowed under the contract.
Here is the good news. That is almost always avoidable. And it usually comes down to a few words in the contract that most people do not know to look for.
This guide shows you those words. It also shows you the questions to ask, the site costs nobody talks about, and the one thing you can do before construction starts that kills the most common regret of all. Read it before you sign anything, with any builder, including us.
A fixed price with allowances is not a fixed price
We will say that again, because it is the most important line in this guide.
If a contract has an allowance in it, it is not a fixed price.
An allowance is just a guess. The builder does not know the real cost yet, so they drop a number in to get the contract signed. It looks precise. It sits inside a document with fixed price written at the top. But it is a placeholder, and placeholders move.
Here is how that plays out in real life.
The contract says you have $20,000 allowed for your kitchen. Great. You sign. Then you sit down and choose your actual kitchen, with the benchtop you want, the appliances you want, the finish you want, and it comes to $50,000. Now you owe the extra $30,000. Nobody lied. Nobody broke the contract. The word "allowance" did the work, and it did it quietly, months after you had committed.
Allowance
a guessed price for something you have not chosen yet.
Provisional sum
a guessed price for work the builder has not fully worked out yet, often site works.
Prime cost
a set amount for a product you will pick later, like taps or appliances.
One or two of these is normal in the industry, and their presence alone does not mean a builder is dishonest. But every single one is a number that can still go up after you have signed, and the risk of that increase sits with you, not the builder. If a contract is full of them, the fixed price is not fixed. It is an estimate wearing a nicer name.
Why paying for a proper quote actually saves you money
Most people think paying for a quote only helps the builder. It is the other way around.
Doing the work up front is the only way a builder can give you a real fixed price and stand behind it. There is no shortcut. Either the unknowns get found and priced before you sign, or they get found and charged after.
At Highwater Homes we do that in what we call the preliminary stage. Before you sign a build contract, we get your selections locked in and we investigate the block. We get real, fixed prices from our kitchen company, our electrician, our suppliers, not guesses. We do the site reports, the drawings, the engineering. We sit with you while you make the decisions most builders leave until after the contract, precisely because leaving them until after the contract is what makes prices blow out.
For a design and build, that stage can cost up to $40,000, which includes council approval fees. This amount isn't an extra cost — it's part of your overall build price regardless of when it's paid. If you already have approved plans and just need a price, we charge a tender fee of $5,000.
Yes, that is money spent before you have a contract. But here is what it buys you: when we hand you the fixed price, the surprises have already been found and priced. The soil has been tested. The slope has been surveyed. The kitchen has been quoted by the people who will actually build it. The only thing that changes the number after that is you, if you change your mind on something.
A free quote pushes the cost of the unknowns to after you sign, when you can least afford to say no. A paid preliminary deals with them before, when you still have every option on the table. Only one of those lets you plan.
The costs that never show up in a quick quote
The ground you build on is where a price runs away fastest. Three things drive it, and you cannot see any of them when you walk the block.
Slope. A block that looks flat often is not. We do a contour survey, and a block the owner swore was level can have a metre to a metre and a half of fall across it. That does not sound like much when you say it out loud. It adds real cost, in retaining, in fill, in engineering, in the slab design itself.
Soil. We do a soil test, where a machine digs test holes to see if you are building on sand, clay or rock. That decides your foundations, and foundations are not a place where anyone should be guessing. Two identical homes on two different soil types can carry very different price tags before a single wall goes up.
And here is the one that catches people out most. Soil removal is the biggest waste of money in the building game. If your block slopes and you want a flat home, that soil has to go. Taking it away can cost thousands of dollars. You are paying for the machine, the trucks and the tip, and it adds nothing to your finished home. Not a better kitchen, not an extra room, nothing you can see or touch. Council rules on floor height can force you to dig out even more than the slope alone would suggest.
Estate rules. Around Camden and Macarthur, the trickiest part now is not council, it is the developer. Newer estates have design guidelines that tell you what colours, style and size you are allowed, and you often have to get their approval before council even sees the plans. Those guidelines can add cost by dictating materials and finishes you would not otherwise have chosen.
A builder who checks all of this before the contract can price it properly. A builder who has not will reach for an allowance, and you will meet the real number later.
The questions to ask before you sign
Take these to any builder. Write the answers down.
- Does this contract have any allowances, provisional sums or prime costs? Show me every one.
- If the real cost of any of them comes in higher, who pays, me or you?
- Have you done a contour survey and a soil test? Is the site cost a fixed figure or a guess?
- Are there estate design guidelines on my block, and does this design meet them?
- What will I actually pay if I change nothing? Show me in writing.
If the answers are vague, the price is not fixed. If they are specific, you have found a builder who did the work up front. It really is that simple. The quality of the answers tells you the quality of the preparation, and the quality of the preparation is what protects your number.
One more kind of regret, and how we kill it early
Even a price that holds does not protect you from the other regret: a home that is the wrong size for how you live.
You cannot feel a floor plan. A room looks fine on paper, then the walls go up and it is too tight. By then, changing it means demolition, redesign and real money.
So before we build, we set your plans out at full size and walk you through them, with fake kitchen benches, a dining table and lounges in place. Suddenly you can see that there is not enough room between the lounge and the dining table, or the lounge is too close to the wall with the TV. We have made rooms bigger off the back of that walk. In the bedrooms we check the bed, the bedside tables, the doorways and the windows all fit the way you live, not the way a floor plan template assumed you would.
Change it then and it costs almost nothing. Change it after the plasterboard is on and it costs twice as much.
Our clients tell us they were nervous to speak up because they had signed a contract. Please speak up. There is no silly question. If a change can be done at a fair cost, we would much rather do it than have you live with a regret for the next twenty years.
What to do next
If you are close to signing with anyone, run their contract through the three words and the five questions first. Do it before you sign, not after. Ten minutes with a highlighter now is worth more than any argument you could win later.
If you would like a second set of eyes, call Toby directly on 0483 943 309, or book a time here: https://highwaterhomes.com.au/book-in-a-call-with-toby/(opens in new tab). We will look over the fixed price you have been given and point out any allowances hiding in it, whether or not you ever build with us.
One honest tip while you are researching online. AI generated images of homes often look amazing and cannot actually be built. Treat them as a mood board, not a plan.
Highwater Homes. Builder licence BLN 110940C. Custom homes across Macarthur, Camden, the Illawarra and the Southern Highlands.
Where to start
If you are about to sign, take this article to the table with you and ask the five questions above. Any builder worth signing with will answer all five without hesitating.
If you are earlier than that and still choosing a block, talk to a builder before you buy. It costs nothing and it prevents the most expensive mistake in the whole process.
And if you want to go deeper on any part of this, each section above has its own article: what makes a contract genuinely fixed, why a paid preliminary saves money, how to read a block before you buy, and how to choose a builder you will not have to manage.
Frequently Asked Questions
Still planning your build? Learn more about our approach to custom home building and our step-by-step building process. Below are the questions we hear most often about fixed-price building contracts.