Three questions. Straight answers.
Most people planning a major renovation have the same three questions and struggle to get a straight answer to any of them. What will it actually cost. How long will it actually take. And how do I know this builder is not going to hurt me.
This guide answers all three. It also goes through the five decisions that cost homeowners the most money, which in our experience are almost never the ones people worry about.
We renovate homes across the Redlands and South East Brisbane. Cleveland, Capalaba, Mount Cotton, Tingalpa, Point Lookout and the surrounding bay side suburbs. Everything below comes from work we have actually done in this region, not from a textbook.
What a major renovation actually costs
A major renovation or extension is not a kitchen and it is not a bathroom. It is structural work that changes how the house functions. Opening up the back of a house, adding a second storey, extending the footprint, reworking the whole layout.
That number matters less than the gap between the quote and the final invoice. That gap is where people lose money, and it is almost always caused by the contract rather than by the building.
Two things drive it.
The first is a cost plus contract, where you pay the actual cost of the work plus the builder's margin. You sign without knowing the final number, and you find out as you go.
The second, and far more common, is a fixed price contract that is full of allowances. It looks fixed. It says fixed price at the top. But every allowance inside it is a guess, and every guess is a place where the price can move after you have signed.
How to tell if a fixed price is really fixed
Watch for three words in any building contract.
Allowance.
A guessed price for something you have not chosen yet. The contract says you have $20,000 allowed for your kitchen. You sign. Then you choose the actual kitchen, with the benchtop you want and the appliances you want, and it comes to $50,000. You owe the extra $30,000. Nobody lied. Nobody broke the contract. The word allowance did the work quietly.
Provisional sum.
A guessed price for work the builder has not fully scoped yet. Often site works, drainage, or anything underground.
Prime cost.
A set amount for a product you will pick later, like tapware or appliances.
One or two of these is normal in the industry, and their presence does not mean a builder is dishonest. But every one is a number that can rise after you have signed, and the risk 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.
We do not do vague quotes or shifting allowances. We scope the job properly first, price the real thing, and put a fixed number on it before work starts. That takes longer up front. It is the only way the number at the end matches the number at the start.
How long a major renovation takes
Two stages, and people usually only think about the second one.
4–5
months
Design, approvals & pricing
5–8
months
Construction
We commit to a completion date and we back it. Almost nobody in this industry will put a date in writing, which should tell you something about how often dates get missed. Your completion date is set out in your construction contract, and if we miss it because of something on our end, we pay you for every day we run over. The only exception is a delay you've caused, like changes you ask for partway through the build.
The five decisions that cost people the most
1. Choosing on price alone
We are not the cheapest. We do not aim to be. That sounds like something every builder says, so here is what it actually means. When three builders quote the same job and one is well below the others, the low number is almost never because that builder found efficiencies. It is because they have priced less work, made more assumptions, or intend to recover the difference through variations later.
The cheapest quote and the cheapest project are rarely the same thing. The quote is a number on a page. The project is what you actually pay by the end.
Ask any builder who comes in low what they have assumed. Then ask what happens when those assumptions turn out to be wrong.
2. Cutting scope to fit the quote
instead of fixing the scope
When a quote comes back higher than expected, the instinct is to start removing things. Take out the ensuite. Downgrade the windows. Skip the deck.
Sometimes that is the right call. Often it is not, because the things people cut first are the structural and fabric items that are cheap to do now and expensive to do later. Insulation, glazing, waterproofing, the framing to allow a future opening. Nobody sees them and they decide the next twenty years.
The better sequence is to look at the scope before the finishes. A layout change that removes structural work saves more than three rooms' worth of downgraded fittings, and you do not live with the compromise.
3. Not getting the house properly
investigated before pricing
An existing home hides things. Old footings, previous work done without approval, drainage that does not go where the plans say, termite damage, asbestos in a wet area, a wall that turns out to be structural.
If a builder prices your renovation without investigating properly, they are guessing, and you carry the cost of every wrong guess as a variation.
This is why the concept and feasibility stage matters and why it is not free. For a fee of $950, you get a concept plan for your renovation and a cost estimate you can rely on, based on what's actually in your home rather than what we assume is there.
Investigating properly costs money up front and saves multiples of it later.
4. Not reading the contract properly
Most people read the price and the completion date and skim the rest. The parts that matter most are the parts nobody reads.
The allowance schedule, and how much of the total it represents. What triggers an extension of time, and whether the list is so broad that no date is really committed. What happens to the price if the soil classification comes back worse than assumed. The progress payment schedule, and whether the amounts match the work actually completed at each stage. The defects liability period, and what happens after it ends.
If your builder will not walk you through those line by line before you sign, that is the answer to a different question you were also asking.
5. Not spotting a difficult builder early
You can usually tell in the first fortnight, well before any money changes hands, and the tell is almost always communication.
Watch what happens when you ask a question with an uncomfortable answer. Do you get a straight response quickly, or a reassuring non answer slowly. Watch whether you have to chase for things you were promised. Watch whether the person selling to you is the person who will run your job.
Then ask the question that sorts most of it. What happens on my build when the person running it is on holiday for a fortnight. If the honest answer is that things stop, you have found your risk, because that business runs on one person's memory rather than on a system.
Where to start
If you are about to sign something, take this article to the table 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 working out whether the project is viable, talk to a builder before you spend money on drawings. It costs nothing and it prevents the most expensive mistake in the process, which is designing something that was never going to work on your block or your budget.
We are happy to have that conversation whether or not you build with us. Call the office on 0489 080 958 or book a discovery call.
Winner, 2025 Master Builders Brisbane Region Award for Best Renovation/Remodelling Project ($300,000–$450,000).
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