Change Orders and Margin Drift: How to Stop Them From Quietly Killing Your Profit

Ask most contractors how a profitable-looking project ended up breaking even, and the honest answer is rarely one big mistake. It's usually a long list of small ones: a material substitution here, a few extra labour hours there, a change order that got verbally agreed on site and never formally priced. Individually, none of it looks dangerous. Added together over a project, it's called margin drift — and it's one of the most common reasons profitable contracts stop being profitable.

What Margin Drift Actually Looks Like

Margin drift is the gradual, often invisible erosion of a project's profit margin over time, as small unbudgeted costs accumulate faster than they're tracked. It rarely shows up as a single alarming number. It shows up as a margin that was 18% at the start of the job and is quietly 9% by the end, with no single event you can point to as the cause.

How Change Orders Drive It

• Verbal agreements that never get priced. The client asks for "just one small change" on site, it gets done, and the cost impact never makes it into any document.
• Change orders priced at cost, with no markup added. If your original quote had a margin built in and the change order doesn't, every variation quietly dilutes your overall percentage.
• Change orders tracked separately from the main budget, so nobody sees the cumulative effect until the project is closing out.

A Simple Way to Track It

The fix is structural, not about trying harder to remember. Every change order — however small — needs a written record with its cost impact, and that record needs to feed directly into the same budget you're tracking everything else against. When change orders and base costs live in the same system, margin drift becomes visible in real time instead of at project close.

Building It Into Your Weekly Routine

The habit that actually prevents margin drift is simple: before closing out each week, check current margin against your original target, not just your remaining budget. A remaining budget can still look fine while your margin percentage is already sliding — they're not the same signal, and relying on only one of them is how drift goes unnoticed.

Casual Legacy | Build tracks change orders alongside your base budget by design, so margin drift shows up on the dashboard the moment it starts — not three months later when it's too late to fix.