Cash Flow Forecasting for Contractors: The 13-Week Model That Prevents Emergencies

In 15 years of working with contractors, I've never seen one go under because they couldn't find work. They go under because they run out of cash. The project is profitable on paper, but the cash isn't there when payroll hits on Friday.

This is the fundamental challenge of construction: you spend money months before you collect it. Materials, labor, equipment — all paid upfront. Payment from the GC? 45-90 days after you bill. And that's if there are no disputes.

Why Standard Cash Flow Statements Don't Work for Contractors

Your accountant's cash flow statement (the one in your financial package) is backward-looking. It tells you what happened last month. For contractors, you need to know what's happening next week, next month, and 90 days from now.

That's where the 13-week cash flow forecast comes in.

The 13-Week Model

A 13-week (rolling quarter) cash flow forecast breaks your cash position into weekly buckets. Here's the structure:

Cash In (weekly):

• Progress billings expected to collect (based on billing schedule + historical collection time)
• Retention releases expected
• Change order payments
• Other income

Cash Out (weekly):

• Payroll (including burden)
• Materials & supplies (based on job schedules)
• Subcontractor payments
• Equipment payments/rentals
• Insurance premiums
• Overhead (rent, utilities, office)
• Tax payments (quarterly estimates, payroll taxes)
• Debt service

Net Position:

• Starting cash + Cash In − Cash Out = Ending cash each week

How to Build It

Week 1-4: High Confidence

You know what's billing this month. You know what payroll is. You know which subs are due. These weeks should be 90%+ accurate.

Week 5-8: Medium Confidence

Based on project schedules and billing cycles. You know the general timing but specifics may shift. 70-80% accuracy.

Week 9-13: Directional

Based on backlog, anticipated starts, and historical patterns. 50-60% accuracy — but still invaluable for spotting potential shortfalls.

The Rules

1. Update it every Monday. Roll forward one week, add a new week 13, and update actuals for the prior week.
2. Be conservative on collections. If the GC pays in 45 days on average, model 50 days. Hope for the best, plan for the worst.
3. Include everything. Quarterly tax payments, annual insurance renewals, equipment balloon payments — these "surprises" shouldn't be surprises.
4. Flag the danger zone. Any week where your ending cash drops below 2 weeks of payroll is a red flag. You need a plan before you get there.

What to Do When You See a Shortfall

The whole point of forecasting is early warning. When you see a cash crunch coming in 6-8 weeks, you have options:

• Accelerate billing: Can you bill earlier on any jobs? Front-load materials billing?
• Slow payments: Negotiate extended terms with key vendors (communicate early, not when you're already late)
• Line of credit: Draw on your LOC before you need it, not after
• Retention release: Push for early retention release on completed jobs
• Delay starts: If a new job will require significant upfront spend, can you push the start date?

None of these options exist if you discover the shortfall on Thursday when payroll is due Friday.

The Payroll Problem

For labor-heavy subcontractors, payroll is the #1 cash drain. You're paying your guys every week (or biweekly), but you're billing monthly and collecting 30-60 days after that. On a $500K job with 60% labor, you might have $150K in labor out the door before your first payment arrives.

This is why your billing schedule matters as much as your contract price. Net-30 vs. Net-45 on a labor-heavy job can be the difference between making payroll and not.

Get Help With Cash Flow Management

Cash flow forecasting is one of the core services in our fractional controller engagement [blocked]. We build and maintain your 13-week forecast, flag potential shortfalls 60+ days in advance, and help you make proactive decisions instead of reactive ones.

Related reading:

• Understanding construction accounting fundamentals → [blocked]
• The retainage trap and how to manage it → [blocked]
• Schedule a free consultation →