When you’re pricing a building job and the client hasn’t yet chosen their tapware, tiles or appliances, how do you quote for something nobody’s selected yet? The answer is prime cost items — a standard way of handling the supply of goods whose final choice, and therefore final price, isn’t known when the contract is signed. Getting prime cost items right is essential to fair, accurate building contracts, and misunderstanding them is a common source of disputes and budget surprises. Understanding how they work protects both builders and clients.
This guide explains what prime cost items are, how they differ from provisional sums, why they matter, and how to handle them — written in plain terms for Australian builders, contractors and clients. It’s general information, not legal or contract advice, so check your contract and seek advice on specifics.
WHAT ARE PRIME COST ITEMS?
Prime cost items are an allowance in a building contract for the supply of goods or materials that haven’t yet been selected when the contract is signed — things like tapware, tiles, appliances, door hardware or light fittings. Because the client hasn’t chosen the specific product yet, the builder includes an estimated allowance for the supply cost, to be adjusted once the actual item is selected.
The key feature of prime cost items is that they cover the supply of an item, not the labour to install it. They’re a way of pricing a job fairly when the exact goods, and their exact cost, aren’t yet known — giving a reasonable estimate now that gets trued-up to the real cost later.
PRIME COST ITEMS VS PROVISIONAL SUMS
Prime cost items are often confused with provisional sums, but they’re different, and understanding the distinction matters. These are an allowance for the supply of goods that haven’t been selected yet — the “what product” isn’t decided. A provisional sum, by contrast, is an allowance for a portion of work that hasn’t been fully designed or scoped yet — the “what work” isn’t fully defined, and it typically covers both labour and materials for that work.
In short: they are about supplying an unselected item, while provisional sums are about carrying out work that isn’t yet fully specified. Both are allowances that get adjusted to actual cost, but they deal with different kinds of uncertainty, and using the right one for the right situation keeps a contract clear and fair.
WHY PRIME COST ITEMS MATTER
Prime cost items matter because they are a common source of confusion, disputes and unexpected costs in building projects. When a client selects an item that costs more than the allowance, the difference is added to the contract price — and if that wasn’t clearly understood upfront, it can come as an unwelcome surprise and a source of conflict.
Clarity is therefore essential. Both builder and client need to understand that prime cost items are estimates that will be adjusted to the actual cost of whatever is selected — up or down. When that’s clear from the start, prime cost items work smoothly; when it isn’t, they become one of the more common friction points in a build.
HOW PRIME COST ITEMS ARE ADJUSTED
The heart of how prime cost items work is the adjustment process. When the contract is signed, the builder includes a reasonable allowance for each prime cost item based on an estimate of what the client is likely to choose. Then, once the client actually selects the specific product, the real supply cost is compared to the allowance, and the contract price is adjusted for the difference. If the chosen item costs more than the allowance, the extra is added; if it costs less, the contract price comes down. This is why the allowances need to be realistic in the first place — an allowance set too low to make a quote look cheaper simply creates a nasty surprise later when the client’s real selections push the price up, damaging trust and often sparking a dispute. Good practice is to set prime cost allowances at genuinely realistic levels for the quality of items the client is likely to want, so the final adjustments are modest and expected rather than large and shocking. Transparency about how the adjustment works, and realism in the allowances, are what make prime cost items fair to everyone.
HOW TO HANDLE PRIME COST ITEMS
1. Use them for unselected supply items
Apply prime cost items to goods not yet chosen, like fittings and appliances. This is exactly what they’re designed for.
2. Set realistic allowances
Base each allowance on what the client is genuinely likely to select. Realistic prime cost items avoid nasty surprises later.
3. Be clear they’ll be adjusted
Make sure the client understands the allowance trues up to actual cost. Clarity is what prevents prime cost items causing disputes.
4. Keep supply and install clear
Remember prime cost items cover supply; treat installation labour separately. Mixing them up creates confusion.
5. Document selections and adjustments
Record what’s chosen and how the price is adjusted. Good records keep prime cost items transparent and fair.
COMMON PRIME COST ITEMS MISTAKES TO AVOID
- Setting allowances too low. Understating prime cost items to look cheap creates painful adjustments and disputes later.
- Confusing them with provisional sums. Prime cost items are for unselected supply goods; provisional sums are for undefined work.
- Not explaining the adjustment. If clients don’t understand allowances true up to actual cost, surprises turn into conflict.
- Poor documentation. Failing to record selections and adjustments makes prime cost items hard to justify.
Getting building contracts and pricing right is core ACS Consulting territory. The Construction Estimation & Cost Consultancy service helps you handle prime cost items and provisional sums correctly so your contracts are clear, fair and dispute-free, while the Operations & Process Improvement service builds the documentation discipline that keeps adjustments transparent, and the Strategy & Business Planning service supports the client trust that clear pricing builds. The free Perth SME Operational Audit Checklist helps you tighten your estimating and contract processes. For authoritative guidance, the Australian Institute of Quantity Surveyors, Master Builders Australia, and the Australian Government’s managing money resources are useful references. As this isn’t contract advice, check your contract and seek advice on specific prime cost items.
FREQUENTLY ASKED QUESTIONS
What are prime cost items?
Prime cost items are an allowance in a building contract for the supply of goods or materials not yet selected when the contract is signed — things like tapware, tiles, appliances and fittings. The builder includes an estimated allowance for the supply cost, which is adjusted to the actual cost once the client selects the specific product.
What’s the difference between prime cost items and provisional sums?
A prime cost item is an allowance for the supply of goods not yet selected — the product isn’t chosen. A provisional sum is an allowance for work not yet fully designed or scoped, typically covering labour and materials for that work. Prime cost items deal with unselected supply items; provisional sums deal with undefined work.
Why do prime cost items matter?
Because they’re a common source of confusion and disputes. When a client selects an item costing more than the allowance, the difference is added to the contract price — and if that wasn’t clearly understood upfront, it’s an unwelcome surprise. Clarity that allowances adjust to actual cost is essential to keeping them fair.
How are prime cost items adjusted?
The builder sets a reasonable allowance at contract signing. Once the client selects the actual product, its real supply cost is compared to the allowance, and the contract price is adjusted for the difference — up if it costs more, down if it costs less. Realistic allowances keep these adjustments modest rather than shocking.
CONCLUSION
Prime cost items are allowances for the supply of goods not yet selected when a building contract is signed, adjusted to actual cost once the client chooses. Use them for unselected supply items, set realistic allowances, be clear they’ll be adjusted, keep supply and installation separate, and document selections carefully.
Because prime cost items are a frequent source of surprises and disputes, realism and transparency are everything — set honest allowances and explain how they adjust, and they become a fair, smooth part of a building contract rather than a friction point. As this isn’t contract advice, check your contract for specifics.
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