Managing Subcontractors Without Losing Margin

General contractors lose 10 to 20 percent of margin per project to sub coordination mistakes. Sub shows up on the wrong day. Sub bills for scope you did not authorise. Sub misses an inspection deadline. Sub disappears at 80 percent complete. Every one of those events costs real money, and it happens because most GCs manage subs on text messages and memory. Here is the sub management playbook that keeps margin intact on every project.

Rule 1. Every sub gets a written scope with a fixed price

No hourly. No time and materials except in true emergency scenarios. A written scope of work with a fixed number gets signed before the sub sets foot on your job. This one rule prevents 60 percent of the margin leak that happens across the industry.

The scope needs to say. Exactly what is included. Exactly what is excluded (the classic "assumes existing framing is square" caveat). Materials responsibility (are you supplying or is the sub). Timeline with start and finish dates. Payment schedule tied to milestones. Warranty terms.

Rule 2. Pay subs on milestones, not on completion

Same milestone billing logic you use with clients. Deposit at signing (10 to 20 percent). Progress payments at physical milestones. Final 10 to 15 percent held back until punch list clear.

A sub who has 100 percent of their money before the punch list has zero incentive to come back. A sub with 10 to 15 percent still outstanding shows up next week. This is the single biggest lever on sub follow through.

Rule 3. Collect a Certificate of Insurance before every sub sets foot

The sub's Certificate of Insurance must name your business as additional insured for the duration of their scope. Non negotiable. If the sub's crew injures your homeowner client's dog and the sub is uninsured, you get sued personally and your GL is the only thing between you and losing your business.

Renovate ships a per sub COI attachment slot so every project record has the current COI stapled to it. When your umbrella carrier audits you, having every COI on file cuts audit friction to zero.

Rule 4. W9 collected before the first check

Every sub over 600 dollars in the tax year needs a 1099. Collect the W9 at contract signing so you never chase paperwork at tax time. Missing 1099s are how the IRS reclassifies subs as employees, which triggers back payroll taxes and penalties across multiple years.

Rule 5. One text thread per project, not per sub

Most GC sub communication is chaos across 8 separate text threads. Every question needs re asking on the right thread. Deadlines fall through cracks because the wrong sub was pinged.

Move sub coordination to your project record inside your CRM. Every sub for a given project sees the same schedule, the same punch list, the same due dates. When rough in inspection moves 3 days, every sub gets the notification.

Rule 6. Lock in sub availability before you sell the project

The classic mistake is selling a 10 week project without checking the plumber and electrician calendars. Halfway through demo you learn the sub cannot start for 4 weeks. Now you either eat the delay cost or scramble a second choice sub at a 20 percent premium.

The fix. Before you send the client the final estimate, text your top 3 subs across each trade with rough dates. Get verbal commitment. Only then quote the timeline.

Rule 7. Build a real bench of subs before you need it

The single best sub in any trade will eventually be booked, sick, or on vacation. If you only have one plumber you trust, the day they are unavailable is the day your schedule blows up. Build a bench of 2 to 3 reliable subs per trade before you need them. Give the primary sub 70 percent of your work, the secondary 20, the tertiary 10, so all three stay warm.

The paperwork trail per sub

Every subcontractor engagement should generate this trail. If you do not have all seven, you have exposure.

1. Signed written scope of work with fixed price
2. W9 tax form on file
3. Certificate of Insurance naming you additional insured
4. Signed milestone based payment schedule
5. Written change order for every scope change
6. Final punch list signed by both parties
7. Final invoice with completion date