Most blown construction budgets do not come from one big surprise. They come from a slow drip of change orders — a relocated outlet here, an upgraded finish there, a "while we're at it" addition — each one small enough to wave through, all of them together adding 15 or 20 percent to a job that was supposedly fixed. By the time the pattern is obvious, the money is spent and the schedule has slipped. Change orders are not the enemy; uncontrolled change orders are.
The takeaway up front: a change order is a contract amendment, and it should be treated with the same discipline as the original contract. Price the time and cost before the work starts, separate genuine scope changes from defects you should not be paying for, and record every change in a running log the day it happens. The single trick that prevents most overruns is refusing to let any extra work proceed on a verbal "go ahead" — no signed change order, no work.
What a change order actually is
A change order is a written, agreed modification to the original construction contract. It alters the scope, the price, the schedule, or all three. Legitimately, it covers things like an owner-requested upgrade, an unforeseen site condition (rock where soft soil was assumed, asbestos behind a wall), or a design clarification that adds work nobody priced originally.
What a change order is not is a way to fix the contractor's mistakes at your expense. If the work was in the original scope and was done wrong, putting it right is rework — a warranty obligation — not a change. Confusing the two is where owners quietly overpay. The first question on any proposed change is therefore: was this in the original scope? If yes, it is not a change order, whatever it is labelled.
This control sits inside the wider project, so it helps to see where it fits in the overall sequence covered in our construction project guide.
The hard problem: changes feel small in the moment
Each change is presented in isolation and sounds reasonable. "It's only a few hundred to move the panel." "The upgraded tile is just the price difference." Individually, none of them is worth a fight. Collectively, they are the budget. The psychology works against you: there is social pressure to keep things moving, the contractor is standing there waiting for an answer, and saying "let me cost that first" feels like being difficult.
The discipline that beats this is mechanical, not heroic. You do not need to win an argument on the spot. You need a process that makes "price it and log it first" the automatic default, so the decision is never made under pressure with incomplete numbers.
A change-order process that holds
Use the same five steps for every proposed change, no matter how small it looks.
- Capture it in writing. Any change starts as a written request describing exactly what is changing and why. A verbal request becomes a written one before anything else happens.
- Price the full cost — labour, materials, and time. The hidden killer is schedule. A change that costs little in materials can add days of delay, idle other trades, and push completion. Demand a price that includes any schedule impact, stated in days.
- Check it against scope. Decide whether it is a true change, a clarification of something already implied, or rework that the contractor owes you. Only the first justifies extra payment.
- Approve in writing before work starts. No work proceeds until the change order is signed by both sides. This is the load-bearing rule.
- Log it immediately. Add it to a running change-order log the same day, with a running total of cost and schedule impact.
The order matters. Pricing before approval, and approval before work, is what keeps the leverage on your side. Once the work is done, you have lost all negotiating power — you cannot un-pour the concrete.
Worked example: how a 6 percent drift happens
Take a £200,000 renovation with a planned 16-week schedule. Over the job, the following changes come through, each waved past on the spot:
- Move two electrical points and add a circuit: £900, +1 day.
- Upgrade kitchen worktop to the next tier: £2,400, +2 days (lead time).
- Add recessed lighting to the hallway "while the ceiling's open": £1,500, +1 day.
- Unforeseen: rotten joist discovered, must be replaced (a legitimate unforeseen condition): £1,800, +2 days.
- Swap to a different tile after delivery: £2,100 restocking + difference, +3 days.
- Three smaller "while we're here" extras: £1,400 combined, +1 day.
Total: £10,100 — about 5 percent over budget — and +10 days, on a 16-week job that is now a 12-percent schedule slip. Only the joist (£1,800) was genuinely unavoidable. The rest were optional upgrades that felt free because each was approved without anyone watching the running total. A live log showing "£10,100 / +10 days" by change three would have changed the decision on changes four through six.
Common mistakes, and why people make them
- Approving on a handshake. People do it to keep momentum. But once work is done, the price is whatever the contractor invoices, and you have no leverage. Always sign first.
- Pricing materials but not schedule. The cost line is easy to see; the days are not. Schedule impact is where overruns and liquidated-damages disputes actually live. Always make the proposal state days.
- Paying for rework disguised as changes. It happens because owners do not re-read their own scope. Keep the original scope document handy and check every change against it.
- No running total. Each change is judged alone because nobody is looking at the cumulative figure. A log with a running total reframes every new request against what you have already spent.
- No contingency, so changes feel like failure. Build a contingency (commonly 5–10 percent, higher for renovations and unknowns) into the budget from day one. Then a change order spends a planned reserve instead of breaking the budget — and you decide deliberately when the reserve is getting thin.
Edge cases and caveats
Genuine unforeseen conditions — buried services, contamination, structural surprises in an older building — are real change orders and you should expect some on any renovation. The control there is not to refuse them but to require evidence (a photo, an inspector's note) and a priced impact before agreeing. On larger jobs, set a change-order threshold: changes under an agreed figure can be approved quickly by the site manager, while anything above it needs owner sign-off, so small items do not stall while big ones still get scrutiny. And remember that contract terms govern — read how your contract defines changes, notice periods, and pricing before a dispute, not during one. Where the contract or a potential dispute is significant, get professional or legal advice.
Frequently asked questions
What's the difference between a change order and rework?
A change order alters the agreed scope, price, or schedule — for example an upgrade you request or an unforeseen site condition. Rework is correcting work that was already in scope but done incorrectly, which the contractor should fix under warranty. You pay for change orders; you should not pay for rework. Check every proposed change against your original scope.
How much should I budget for change orders?
Set aside a contingency from the start — commonly around 5 to 10 percent of the contract value, higher for renovations and older buildings where surprises are more likely. The contingency is not spending money you have to use; it is a planned reserve so that a legitimate change spends a budgeted figure rather than breaking the budget.
Can I refuse a change order?
You can decline owner-optional changes outright. For genuine unforeseen conditions, you generally cannot avoid the work, but you can require evidence and a priced impact before agreeing, and you can ask whether a cheaper compliant solution exists. What you should never do is let disputed work proceed before the price and schedule impact are agreed in writing.
Why does my schedule slip even when changes are small?
Because cost and time are separate. A change can add little money but several days through material lead times, re-sequencing trades, or idle time while a decision is made. If your change orders only ever priced materials, the schedule impact accumulated invisibly. Insist that every change states its impact in days, not just pounds.
Who should approve change orders?
On smaller jobs, the owner. On larger ones, set a threshold: the site manager can approve minor changes quickly, while anything above an agreed figure needs owner sign-off. Either way, approval must be in writing and must happen before the work starts, because approval after the fact removes your ability to negotiate the price.
Next step
Change orders do not have to be where your budget goes to die. Treat each one as the contract amendment it is: price the cost and the days before any work begins, check it against your original scope so you are not paying for rework, and keep a running log so every new request is judged against the total, not in isolation. Do that, and a build stays on budget by design rather than by luck. For help setting up change control on a project before it starts drifting, talk to the team at ConstiCo.
