Reading Builder Quotes Side by Side: Provisional Sums, Prime Cost Items and the Gaps Outside Both

Reading Builder Quotes Side by Side: Provisional Sums, Prime Cost Items and the Gaps Outside Both

General information for South Australian landowners only. This is not legal, financial or quantity surveying advice. The meaning and effect of any contract term is for an SA property lawyer or a solicitor experienced in building contracts; whether an allowance is adequate for your actual scope is for a quantity surveyor (QS) or building consultant; tax treatment is for your registered tax agent; insurance questions are for your broker or insurer. Statutory requirements, thresholds and standard contract forms are amended over time and the terms of your own contract govern, so confirm the live position and have your own documents read before you rely on anything here.

Why the smaller number is not the answer

Two builders have quoted the same house on the same block. One total is lower. The natural next step is to work out why, and the natural assumption is that one builder is cheaper than the other.

Often they are not. Often the two documents are not pricing the same quantity of certainty.

A building quote is a statement about what is known, in three parts: what has been priced, what has been named but not priced, and what has been neither named nor priced. Typically only the first of those appears as a firm figure. The second appears as an allowance. The third does not appear at all — and it is a common place for the difference between two totals to be sitting.

This article is about reading that third category. It is not about pricing your project — what an allowance should be for your actual scope is a question for a quantity surveyor. It is not about how build costs move over a program either; where cost escalation and the risk of a builder failing belong in your numbers is covered in build-cost escalation and builder insolvency in your feasibility. This piece is narrower: two documents, on a table, today.

The two named categories

South Australian domestic building work is a regulated contracting environment, and both of these terms have published meanings.

A provisional sum is an allowance for an item of work that cannot be priced by the builder when the contract is entered into. Consumer and Business Services gives the example of footing costs where a soil report and engineer's design have not yet been completed. The published requirement worth holding onto is that provisional sums must be fair and reasonable estimates in the circumstances in which they are provided (source: CBS — Form 1: Your building contract, your rights and obligations).

That requirement cuts both ways, and it is the reason a low allowance is not automatically good news. An allowance set below what the work will plausibly cost makes a total look smaller without making a project cheaper. Whether a particular allowance meets the standard, and what follows if it does not, is a question for your lawyer against your own contract.

A prime cost item is an allowance for goods to be supplied — the published examples are things like kitchen stoves and bathroom tiling. If the standard of goods you select is higher than the contract provides for, you may pay the additional cost, plus a surcharge, with the surcharge capped by the regulations (source: CBS — Form 1; SA Law Handbook — Building Work Contracts). What the current cap is, and how it applies to your contract, is for your lawyer to confirm against the regulations in force — this article deliberately does not carry the figure, because a number reproduced from a general article is not a basis for a decision on your own contract.

Note what the surcharge means for comparison. A prime cost allowance may not behave like a budget you can spend freely up to — depending on your contract and the current rules, going above it can cost more than the difference alone. So two quotes with different prime cost allowances are not offering you the same flexibility, even where the totals are close.

The third category: what sits outside both

Provisional sums and prime cost items have one useful property in common: where a quote sets them out, they are visible. You can count them, compare them and ask what each is based on. Whether your own documents actually itemise them, and how clearly, is one of the first things to check in each quote.

The gap that moves totals is the work that appears in neither column because it is outside the scope entirely — excluded, assumed away, or simply not contemplated. Work of that kind, where the project genuinely needs it to finish, generally still has to be done and paid for by someone; what a quote's silence changes is who is expecting it.

The recurring candidates:

• Site works and earthworks beyond a stated allowance — cut and fill, rock, retaining. Where a level change meets a boundary, the question of who pays and who is liable is its own subject: see retaining walls on sloping blocks.
• Footings beyond an assumed site classification. A quote priced on an assumed class and a site that classifies worse are different jobs — reactive clay and site classification covers what drives that.
• Imported or uncontrolled fill discovered on the site, which is a different problem again: uncontrolled fill and Class P sites.
• Service connections and any network upgrade — the electricity leg in particular has its own program: planning the SA Power Networks leg.
• Stormwater beyond the boundary, and the levels it drives: legal point of discharge and detention.
• Council-side works and the conditions attached to an approval — kerb, crossover, reinstatement, and any security over them: the kerb, the crossover and the bond.
• Compliance with current building requirements, where energy and accessibility provisions have moved: the energy and accessible-housing changes adding to SA build costs.
• Driveways, fencing, landscaping, letterboxes, clotheslines — small individually, and routinely excluded together.
• Authority fees and charges, which are not the builder's work at all but are still your money: the statutory side is set out in the SA development application and land division fees guide.

The comparison question is therefore not "which total is lower" but "which of these does each document deal with, and by which of the three methods?" A line that is fixed in one quote, a provisional sum in the second, and absent from both is three different risk positions wearing the same word.

Making two documents comparable

Comparing them as issued tends not to tell you much. Normalising them first is largely a mechanical exercise rather than a judgement one.

A workable method:

1. Build one list of scope items — every item that will exist on the finished project, drawn from the plans and your own knowledge of the site, not from either quote. Using a quote as the list is the error: it can only contain what that builder thought of.
2. Mark each item against each quote: fixed, provisional sum, prime cost, explicitly excluded, or silent. Five states, not two.
3. Treat "silent" as the highest-attention category, not the lowest. An explicit exclusion at least tells you the builder considered it.
4. Compare like categories against like — the sum of provisional sums in each quote against the other, before comparing totals. Two projects with the same total and very different provisional-sum exposure are not the same offer.
5. Ask, in writing, what each allowance was based on — which report, which drawing, which assumed classification. An allowance with a stated basis can be tested. One without a basis is much harder to assess.
6. Have a QS or building consultant test the allowances that matter against your actual site, and your lawyer read the terms that govern how those allowances resolve.

Step 6 is the step most easily skipped, and it is what turns a tidy comparison into a tested one.

The contract terms that decide how the allowances resolve

An allowance is only half the arrangement. The other half is what happens when the real figure arrives, and that lives in the contract's machinery rather than in its price schedule.

South Australian domestic building contracts are regulated in ways worth knowing exist, even though the detail on your contract is your lawyer's to read. On the published general position: contracts above a stated value must be in writing and carry prescribed details, including the builder's licence number; a contract can generally only be varied if both parties agree in writing, although minor changes may occur without the owner's consent; a builder must not demand or request payment unless it is a genuine progress payment in respect of work already performed under the contract; advance payments and deposits are limited; and a building owner has a short cooling-off period after signing in which to terminate, by written notice (source: SA Law Handbook — Building Work Contracts). Pricing structures also differ in kind — a fixed-price lump sum, a rise-and-fall clause and a cost-plus arrangement distribute risk very differently, and cost-plus margins are limited in South Australia.

So the questions that decide what your allowances actually mean:

• How is a variation priced and approved, and does the process require your written agreement before the work proceeds?
• What happens if a provisional sum comes in under? Whether an adjustment runs in both directions is a matter of what the contract says, and is worth putting to your lawyer rather than assumed.
• Does a margin apply to the difference, and to which categories?
• When are progress claims payable, and against what evidence of work performed?
• Which pricing structure is this — and if it carries a rise-and-fall clause, what triggers it?

Ask them of both documents. The answers frequently separate two quotes more sharply than the totals do.

One thing to confirm before you sign, not after

Building indemnity insurance sits slightly outside the comparison exercise, but this is the moment it becomes relevant.

For domestic building work above a stated contract value that requires development approval, the builder is required to take out building indemnity insurance on the owner's behalf, and the published guidance is to check that you have been supplied with a copy of the certificate of insurance before work begins, and to check that the insurance is valid (source: SA.GOV.AU — Building indemnity insurance; SAFA — Building Indemnity Insurance).

The reason it belongs in an article about comparing quotes is that its value tends to become apparent only later, at a point when it can no longer be arranged. What that cover does, and the order in which an owner finds out where they stand when it is needed, is set out in when a builder enters liquidation mid-build. Whether it applies to your contract, and whether what you have been given is valid, are questions for your lawyer and the insurer.

Frequently asked questions

Is a quote with more provisional sums a worse quote? Not necessarily — it may simply be more honest about what is not yet known, particularly where the soil report or engineering is outstanding. What matters is whether each allowance has a stated basis and whether the basis is reasonable for your site. That is a QS question.

Can I ask a builder to convert a provisional sum to a fixed price? You can ask. Whether they will depends on whether the underlying unknown has been resolved — often the honest answer is that it cannot be fixed until the report exists. Getting the report first is sometimes the cheaper move.

Do the two quotes have to be on the same contract form to be compared? No, but the form matters to how the allowances resolve, so the comparison is incomplete without reading both sets of terms. Your lawyer, not the price schedule, answers that half.

What if the difference is mostly in the margin? Then you are comparing two businesses rather than two scopes, which is a legitimate comparison — but you can only see it once the scope difference has been normalised out. That is what the exercise above is for.

Should I just choose the lower quote and manage the extras as they come? That is a decision only you can make, and it depends on how much of the unknown you are able to carry. The point of the exercise is to make the size of what you would be carrying visible before you decide, rather than after.

Who reads what, and where Cyberate PM sits

• The meaning and effect of any contract term — your SA property lawyer or a solicitor experienced in building contracts.
• Whether an allowance is adequate for your actual scope — a quantity surveyor (QS) or building consultant.
• The site facts the allowances depend on — your geotechnical engineer, structural engineer and licensed surveyor.
• Whether the insurance you have been given is valid — the insurer or your broker.
• Tax treatment of any of it — your registered tax agent.

Cyberate PM does none of those. We do not price building work, prepare quantity estimates, give legal opinions on contracts, or certify insurance. We work owner-side: we assemble the scope list the comparison runs off, put the same written questions to each builder so the answers arrive in comparable form, route the allowances to a QS and the terms to your lawyer, and hold the resulting picture in one place so the price conversation and the risk conversation are not happening in two separate rooms. What that role covers is set out in what a development manager actually does, and where it sits against the builder's own management in project manager vs builder.

Before you sign

Get both documents out, side by side, with the plans.

• Have I built the scope list from the project rather than from either quote?
• For every item on it, do I know which of the five states it is in, in each quote?
• Which items are silent in both documents?
• What is the total provisional sum exposure in each, and what is each allowance based on?
• Has a QS tested the allowances that could move materially?
• Has a lawyer read the variation, progress payment and adjustment machinery in both?
• Which pricing structure is each quote, and what triggers any rise and fall?
• Have I been given a certificate of insurance, and has my lawyer, broker or the insurer confirmed it rather than my having filed it unread?

Once two quotes have been through that exercise, a price comparison between them starts to mean something. Before it, a difference in totals may be telling you about scope rather than about price.

Statutory thresholds, prescribed contract requirements and regulated caps are amended from time to time, and the terms of your own contract govern. Confirm the current position with your own adviser before acting. Reflects publicly available material as at August 2026.

Sources

• Consumer and Business Services — Form 1: Your building contract, your rights and obligations
• SA Law Handbook — Building Work Contracts
• SA.GOV.AU — Building indemnity insurance
• SAFA — Building Indemnity Insurance: Homeowners
• Consumer and Business Services — Rights and protections when home building