Provisional sums, PC items and site costs: why the cheapest builder quote is not always the cheapest build

Ask any forum full of Australian first home buyers what caught them out, and the same three phrases come up again and again: provisional sums, PC items, and site costs. They are the parts of a builder quote that are estimates rather than fixed numbers, and they are the main reason a quote that looks cheap on paper can end up costing more than the one it beat.

None of this makes builders the bad guys. These allowances exist for a genuine reason: some costs cannot be known until work starts. What trips buyers up is not the allowances themselves. It is that no two builders write them the same way, so the numbers on two quotes are not measuring the same thing.

What these terms actually mean

A provisional sum is an allowance for work the builder cannot fully price yet. Site excavation is the classic example. Nobody knows exactly what is under your block until the machines arrive, so the quote carries an estimate. If the real cost comes in higher, you pay the difference.

A PC item (prime cost item) is an allowance for a product that has not been chosen yet, like tapware, tiles or an oven. The quote might carry $40 per square metre for tiles. If the tiles you fall in love with cost $75, the gap is yours.

Site costs cover getting your block ready to build on: cut and fill, soil conditions, service connections, retaining. On some quotes this is a fixed figure. On others it is an allowance that can move.

Where the comparison breaks

Here is the pattern buyers describe over and over. Quote A comes in $18,000 cheaper than Quote B. It wins on price, the contract gets signed, and then the allowances start landing at their real numbers. A low site cost allowance rises. Basic PC allowances get upgraded, because almost nobody builds their first home with the bottom-of-range oven. By handover, Quote A has grown past what Quote B promised as a firmer figure on day one.

The problem was never the price. The problem was that the two quotes were not comparable as written. One builder priced generously and fixed more of the number. The other carried lean allowances that were always going to move. Lining them up by the bottom-line figure compares the numbers, not the houses.

What you can actually do about it

You do not need to become a quantity surveyor. You need the two or three quotes in front of you translated to the same standard, so you can see which numbers are fixed, which are allowances, and how generous each allowance really is. That is a reading exercise, and it is exactly the reading most of us have never had to do before, because the builder writes quotes every day and most people read one, once.

That is the gap BuildScore™ was built for. Send us your competing quotes and a Builder Quote Comparison report comes back with each one scored across five categories, including Price & Value and Inclusions, against fixed criteria, with an experienced, real person finalising every score. We do not pick a winner, and we do not tell you what your contract terms mean legally. That is a question for your conveyancer or building solicitor. We show you what sits behind every number, side by side, so the conversation you have with your builder, your broker and your solicitor starts from level ground.

BuildScore™ is an independent information and comparison service. Reports are based on general industry data and analysis. Not financial, legal or building advice. Always engage qualified professionals before signing any contract.