Very few construction projects finish at the price in the signed contract. The difference is almost never one dramatic event. It is the accumulation of change orders, each of them reasonable on its own, approved under schedule pressure and priced without competition.
Owners tend to treat change orders as bad luck. The evidence points the other way: most of them originate before the first bid is submitted, which means most of them can be designed out. This guide covers what a change order is, how much it typically adds, how it should be priced and where the real prevention happens.
What a change order is and what it is not
| Instrument | When it is used | Effect on price |
| Change order | Owner and contractor agree on a change in scope, price and time | Contract sum is adjusted on signature |
| Change directive | Owner orders the work before the price is agreed | Price is settled afterwards from cost records |
| Allowance adjustment | The actual cost of an allowance item differs from the figure carried in the bid | The difference is added or credited |
| Minor field change | A clarification with no cost or time impact | None |
The distinction matters because each instrument shifts risk differently. A signed change order closes the question. A directive keeps the job moving but leaves the owner exposed to whatever the cost records later show, which is why it should be the exception and should always carry a not to exceed figure.
How much change orders really add
Published figures vary with project type and with how complete the design was at bid time.
| Context | Reported increase over contract value |
| Reviews of United States building projects | 5 to 10 percent |
| Range often quoted as the industry norm in public audits | 8 to 14 percent |
| Programs with early scope definition and constructability review | Under 5 percent |
| Renovation of older buildings | Upper end of the range or beyond |
Renovation sits at the top for a simple reason: nobody can price what is hidden behind a wall. That is why contingency guidance differs so sharply, with 5 to 10 percent treated as adequate for new construction and 15 to 20 percent as prudent for older buildings, including most New York apartments and brownstones.
Where change orders come from
| Cause | Typical weight | Who can prevent it |
| Design errors and omissions | The largest source in most studies | Owner and design team, before bidding |
| Owner driven scope changes | Close to a third | Owner |
| Unforeseen site conditions | Around 5 to 10 percent | Investigation before design is final |
| Code, inspection and supply issues | The remainder | Design team and contractor |
One widely cited analysis attributes roughly two thirds of changes to design errors and omissions, close to a third to scope changes requested by the owner and about five percent to conditions nobody could have foreseen. The exact shares move from study to study, but the pattern is stable: the great majority of change orders are created by documents and decisions, not by surprises in the ground.
What a valid change order contains
- A description of the change that refers to specific drawings or specification sections
- The reason for the change and who initiated it
- A price broken down into labor, materials, equipment and markup
- The effect on the schedule, stated in days
- The effect on allowances and on the remaining contingency
- Signatures from both parties before the work proceeds
In New York the last point is a legal requirement and not just good practice for residential work: amendments to a home improvement contract above 500 USD must be in writing and signed by all parties. On commercial projects the same rule usually comes from the contract itself. Courts have sometimes enforced verbal changes where both sides had ignored the written requirement, which is an argument for following it every time.
Pricing: markup, credits and unit prices
A change order is priced without competition, so the rules have to be fixed while competition still exists, in the original contract.
| Element | Common practice |
| Markup on work by the contractor | 10 to 15 percent for overhead and profit combined |
| Markup on subcontracted work | 10 percent for the subcontractor plus 5 percent for the general contractor |
| Credits for deleted work | Actual net cost, with overhead and profit often retained unless the contract says otherwise |
| Additions and credits in one change | Markup applied to the net increase only |
| Unit prices | Agreed in the bid for predictable variables such as added outlets or feet of pipe |
| Time and material work | Daily signed tickets and a not to exceed amount |
The stacking matters more than the headline rate. On 20,000 USD of subcontractor cost, a ten percent subcontractor markup followed by five percent for the general contractor produces 23,100 USD. If the contract is silent, each tier may apply its full rate and the same work can cost several thousand dollars more.
Prevention happens before the bid
- Finish the drawings and finish selections before asking for prices
- Open walls and ceilings in a few places to check concealed conditions
- Replace vague allowances with real quantities and realistic figures
- Ask every bidder to list exclusions and assumptions in writing
- Include unit prices and markup rates in the bid form
- Answer bidder questions in writing and share the answers with all bidders
A bid that comes in far below the others is frequently a bid that expects to recover the difference through changes. The defense is to make every contractor price the same documents and to compare the returns line by line. A construction tendering platform is built around that discipline: the scope is issued once, every bidder responds in the same structure and gaps between offers become visible before a contract is signed instead of after.
Qualifying bidders belongs in the same phase. For work in the city, a shortlist drawn from a public directory of New York City general contractors with license numbers and active status removes one source of trouble before prices are even requested.
Managing changes during the job
- Keep a change log with a running total measured against the contingency
- Require pricing within a fixed number of days from the request
- Allow no extra work without a signed order, except for genuine safety emergencies
- Photograph concealed conditions before they are covered again
- Review open changes at every weekly meeting so that none ages into a dispute
When the running total passes half of the contingency before the project is half built, the budget is already in trouble. That is the moment to reduce scope elsewhere, not the final month.
Frequently asked questions
What is a normal amount of change orders on a project?
Between 5 and 10 percent of the contract value on a well documented new build, and more on renovations of older buildings. A project that stays under 5 percent has usually invested in complete drawings and early investigation.
What markup is fair on a change order?
Ten to fifteen percent for overhead and profit on work the contractor performs directly, and about five percent on top of the subcontractor price for work that is passed through. The rates should be written into the original contract.
Who pays for unforeseen conditions?
Generally the owner, when the condition differs materially from what the contract documents showed and could not have been found in a reasonable site inspection. Where a normal inspection would have revealed it, the cost usually stays with the contractor.
Can a contractor stop work until a change order is signed?
It depends on the contract. Under the standard forms used on larger projects, the owner can direct the contractor to proceed and settle the price afterwards. On smaller residential jobs the contractor is normally entitled to a signed agreement first.
Do change orders have to be in writing?
For New York home improvement contracts above 500 USD, yes, by law. Elsewhere it is a contract requirement, and it should be treated as absolute. Verbal approvals given on site are the main source of disputed final invoices.
How large should the contingency be?
Plan for 5 to 10 percent on new construction with complete drawings and 15 to 20 percent on renovation of older buildings. The contingency belongs to the owner, and unused funds should stay with the owner at the end of the job.
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