Sending the same complete documents to builders so that the prices can be genuinely compared.
Three prices on the same renovation, tens of thousands apart, and no way to tell which one is right. That is the ordinary situation. It is rarely because one builder is greedy and another is generous — it is because each of them was asked to price a slightly different thing, and the differences are invisible in the totals.
A tender is only a comparison when every builder receives an identical set of documents at the same time and prices against it. If one gets a full drawing set with a specification and another gets plans plus a conversation on site, the numbers are not comparable. The low one belongs to whoever assumed the least, and the assumptions reappear later as variations, at a point where you have no competition and no leverage.
Three is the usual number on a house. Two gives you no middle. Five wastes the goodwill of builders who put real unpaid hours into pricing and lose. Tell them who else is pricing it — the good ones ask anyway.
The cheapest quote is usually just the one with the most left out of it.
A tender is only a comparison if everyone is pricing the same thing. Complete documents are what make three prices comparable — otherwise you are comparing three different scopes and the lowest number simply belongs to whoever assumed the least.
The moment of truth, and real fear. Everything up to now has been provisional. The client has spent a great deal of money to arrive at a number that might end the project.
Two verbal quotes for different scopes, compared on the bottom line. The cheaper builder wins by excluding things, and the excluded things reappear during construction as variations at a price nobody is in a position to argue with.
The same complete documents go to several builders, so what comes back is genuinely comparable. That matters more than it sounds. A like-for-like tender across three builders routinely returns a spread wider than the entire architectural fee. Compare two verbal quotes for different scopes and the lowest number simply belongs to whoever assumed the least — and you find out what they left out during construction, at a price you are in no position to argue with.
Three is the working number for a house. Two leaves you with a high and a low and no sense of the middle. More than three or four and you are asking a lot of people to spend days pricing a job most of them will not get, which is how a practice quietly loses access to good builders. Choose them deliberately rather than casting wide: similar work, similar suburb, similar size of job, currently licensed, and with capacity in roughly the window you need. A builder who is too busy will price to be busy.
Four reasons, usually. They priced different scopes, because the documents left room to. They carry different overheads and different margins. They are at different points in their own workload, and a full builder prices high on purpose. And they have made different judgements about risk — an old Queenslander with unknown stumps and unknown wiring gets a contingency baked in, and how big that contingency is depends on how much the drawings told them. Complete documentation narrows the spread. It cannot close it, because the last two reasons are commercial, not technical.
Fixed price for almost every domestic renovation. Under cost plus you pay actual costs plus a margin, with no ceiling, and the QBCC's own published warning is that owners routinely end up paying far more than they anticipated — in some cases more than double. Queensland also places limits on when cost plus can be used for domestic building work, so check the current position with the QBCC before agreeing to one. Cost plus has legitimate uses on genuinely unknowable work, but it transfers all the price risk to you, and you are the party least able to carry it.
Not on the bottom line. Put them side by side in the same trade order and compare the parts: preliminaries and site costs, each trade, the provisional sums, the prime cost allowances, the margin, and the program. Then make a separate column of exclusions and read only that. Most of the difference between three prices lives there. Also check that each price is against the same drawing revisions — if one builder priced revision C and another revision E, you are comparing two different houses. Ask every builder for the breakdown in writing before you compare anything.
Yes, and a negotiated contract with a builder you trust is a legitimate route — it is one of the two standard methods in the Institute's client architect agreement. What you give up is the benchmark. Without a competing price you have no way of knowing whether the number is fair, only whether you can afford it. If you go that way, you can still get an independent cost check on the documents, or ask the builder to open their trade quotes to you. And check their licence, class and history on the QBCC register regardless of who recommended them.
If you would rather start small, the First Sketch Session is two hours at your place. You keep the sketches, and there is no obligation afterwards.