Construction Cash Flow: Why Australian Builders Go Broke on Profitable Jobs
The most counterintuitive fact in residential construction finance: a builder with a full project pipeline and healthy profit margins can run out of money and collapse.
This happens in Australia every year. The ASIC insolvency data for construction is consistently among the highest of any industry — not because builders aren't making margin, but because cash flow timing kills companies that are profitable on paper.
This guide is about why that happens and what to do about it.
The fundamental problem: you spend before you get paid
In residential construction, the cash flow timing problem is structural.
You pay materials on delivery or within 30 days. You pay subbies within 30 days (or face SOPA consequences). You pay your employees weekly. You pay your site supervisor weekly. You pay insurance, levies, and compliance costs progressively.
But you get paid at milestones — slab, frame, lock-up, fix, completion — which can be weeks or months apart. Worse, milestone payments are defined in the contract and often don't track your actual spending curve.
The result: in every residential build, there are periods where you have spent significantly more than you have received. How much you've spent vs received at any point in the job is your cash flow exposure — and every builder carries it, whether they know it or not.
The S-curve: your spending profile on every build
The standard cash flow profile for a residential build follows an S-curve:
- Weeks 1–4: Relatively low spending. Site establishment, footings, slab. You're laying foundations; materials volumes are moderate.
- Weeks 5–10: Steep spending ramp. Frame, roof, windows, external cladding — materials costs spike rapidly.
- Weeks 11–18: Peak spending sustained. Fit-out phase. Electrical, plumbing, joinery, plastering, flooring, painting all happen concurrently. Multiple subcontractors paid simultaneously.
- Weeks 19–22: Spending tapers. Completing trades, finishing, cleaning, defect rectification.
Your inflow curve depends entirely on how your milestones are structured. The three most common milestone structures in AU residential HIA contracts create very different cash flow profiles.
The three milestone structures — and their cash flow traps
Structure 1: Standard HIA milestones (most common)
Deposit (5%) → Slab (15%) → Frame (20%) → Lock-up (25%) → Fix (10%) → Completion (25%)
The maths on a $700,000 contract:
| Milestone | Inflow | Cumulative inflow |
|---|---|---|
| Deposit | $35,000 | $35,000 |
| Slab | $105,000 | $140,000 |
| Frame | $140,000 | $280,000 |
| Lock-up | $175,000 | $455,000 |
| Fix | $70,000 | $525,000 |
| Completion | $175,000 | $700,000 |
In theory, this looks reasonable. In practice, your actual spending curve during the fit-out phase (between lock-up and completion) can outrun the fix payment significantly. You might spend $180,000 between lock-up and completion on trades and materials, but only receive $70,000 at the fix milestone and $175,000 at completion — with completion payment coming well after you've paid the trades.
Maximum cash flow exposure on a standard HIA milestone structure: typically $80,000–$130,000 at some point during fit-out on a $700,000 build.
Structure 2: Front-loaded milestones (risky but popular)
Some builders negotiate larger early-stage payments — higher deposit or a larger slab/frame payment. This reduces cash flow exposure in the early stages but creates legal and ethical risk:
- In VIC, residential building deposits are capped at 5% for contracts over $20,000. Exceeding this without proper authority is illegal.
- HIA and Master Builders contract terms define maximum milestone percentages. Departing significantly from those norms without good reason invites dispute.
- If the owner defaults mid-project on a front-loaded contract, you may find you've received more than you've spent — giving the owner grounds for a claim against you.
Front-loading is a cashflow fix that creates different risks. Understand what you're trading.
Structure 3: Progress billing on cost-plus contracts
Cost-plus contracts allow progress billing based on actual costs incurred, typically monthly. This gives the builder the best cash flow position — you claim what you've spent, roughly when you've spent it.
The downside: owners often resist cost-plus because they don't know the final price. Cost-plus is most viable for high-end custom builds where the design flexibility justifies the owner's exposure. See our guide on cost-plus vs fixed-price contracts for a full breakdown.
The three patterns that bankrupt profitable builders
Pattern 1: Running multiple jobs on the same float
A builder with three concurrent builds each with $100,000 cash flow exposure doesn't necessarily need $300,000 in float. Because the S-curves stagger, the peaks rarely coincide perfectly.
But when they do coincide — all three builds in fit-out simultaneously — the builder needs all $300,000. If they've been managing cash flow based on the "they don't usually overlap" assumption, they hit a wall.
The fix: model the aggregate cash flow position across all active projects monthly. You need to see the combined exposure curve, not just per-project.
Pattern 2: The retention trap
Some commercial and developer clients retain 5–10% of each milestone payment until practical completion. On a $700,000 contract with 5% retention, you're owed $35,000 at completion that you won't receive until all retention conditions are satisfied — which can be 3–12 months post-handover.
On two jobs simultaneously, that's $70,000 outstanding. On five jobs with staggered completions, you might have $150,000+ in retention receivables that don't appear on your bank balance but represent real earned money.
The fix: track retention separately, know when each retention is due for release, and never treat retention as "extra" margin — it's your money, just locked up temporarily.
Pattern 3: Variations not invoiced
Approved variations completed in week 8 that aren't invoiced until week 16. Materials variations that are absorbed and forgotten. Scope changes that "we'll sort out at completion."
Every unapproved, uninvoiced, or deferred variation is a cash flow problem in disguise. The work is done. The cost is incurred. The payment is missing.
On a custom build with significant variation activity, variation receivables of $50,000–$80,000 are common. Builders who manage variations casually are effectively lending their clients money at 0% interest while paying their own trade bills.
The fix: invoice variations within 5 business days of owner approval. Don't bundle them for end-of-job reconciliation.
A practical cash flow model for every project
Before you sign a contract, you should know:
- Expected build duration (in weeks)
- Approximate spending curve (when materials, subbies, and management costs are expected)
- Inflow dates (when each milestone is triggered and when payment is due)
- Maximum cash flow exposure (the largest negative gap between cumulative outflows and cumulative inflows)
- Your available float at contract start
If your maximum cash flow exposure exceeds your available float, you're taking a project you can't fund. That doesn't mean don't take it — it means arrange finance, negotiate better milestone terms, or time the start date against your other project cash flows.
Milestone timing: the levers you actually have
Most builders accept milestone structures as fixed. They're not, within limits.
Negotiate stage completion definitions
Milestone triggers don't have to be "practical completion of frame" — they can be "frame erected, tie-downs installed, and inspector certificate provided." Being specific about what constitutes completion reduces disputes over whether a milestone has been reached.
Add interim claims
HIA contracts allow for builder-initiated progress claims in addition to the standard milestones. For long fit-out phases, include a contractual provision for an interim progress claim at a defined point during fit-out. This can materially reduce your peak exposure.
Subcontractor payment terms
For major subbies, negotiate 30-day payment terms aligned with your own milestone receipts. If you receive your frame milestone on a Friday, you should be able to pay your framer on the following Friday — not before your milestone clears.
Materials accounts
Establish trade accounts with your major suppliers with 30-day terms. Cash purchasing of materials on a large build is an unnecessary cash flow drag.
What the numbers should look like
A well-managed residential builder should have:
- Maximum cash flow exposure per project: No more than 8–12% of contract value
- Work in progress (WIP): Tracked and reconciled monthly — the gap between work completed and amounts invoiced
- Debtors (receivables): Milestones triggered but unpaid should be chased within 14 days of trigger
- Retention receivables: Visible and dated — you know when each is due
If you don't know any of those numbers for your current projects, cash flow risk is invisible to you — which is exactly how it blindsides builders who are "doing well."
How Build Margin helps with construction cash flow
Build Margin's cash flow module projects the cumulative inflow and outflow curve for each project based on your contract milestones and cost schedule — showing your peak cash flow exposure before you start. The Progress Claims feature tracks milestone status, retention, and variation receivables across all active projects in a single dashboard.
Start a free 14-day trial and see your actual cash flow position across all active builds in one place.
Frequently asked questions
How much cash float should a residential builder carry?
A conservative rule of thumb: enough to cover 12–15% of your total contracted work in progress (WIP). On $2,000,000 in active contracts, that's $240,000–$300,000 in accessible working capital. Solo builders on lower volumes can operate with less, but the floor is your peak single-project exposure plus one month of fixed overheads.
What is work in progress (WIP) in construction?
WIP is the value of construction work that has been performed but not yet invoiced or claimed. On any active build, WIP grows between milestone claims and resets to zero when a milestone is claimed. High WIP with no near-term milestone means a cash flow crunch is approaching.
Why do builders go broke near completion?
Completion-stage cash flow is often the tightest point. All the fit-out trades have been paid. The completion milestone — often 25% of the contract — is being held back pending defects and final sign-off. If there are defect disputes, that final payment can be withheld for months while you continue to incur costs resolving them. Builders who've been operating without a float and counting on the completion payment to reset their position get caught here.
How does retention affect cash flow planning?
Retention is real money that you've earned and haven't received. It should appear in your cash flow model as a "delayed receivable" — positive, but with a specific future date. If you exclude retention from your cash flow model, your projected cash position will consistently understate your receivables.
Last updated November 2026. Cash flow figures and milestone percentages are illustrative examples based on standard HIA residential building contract structures. Your actual position depends on your specific contracts, cost profile, and project mix.