What a change order is
A contract fixes the scope, the price and the time. A change order amends one or more of the three. Both parties sign it. Work done on a verbal promise is a common source of unpaid bills.
What causes a real change
- The owner adds or removes work.
- The design team revises the drawings after the contract.
- A hidden condition is found that the documents did not show.
- A conflict in the documents is resolved in a way that adds work.
- A code official requires something the documents did not.
When a missed item is a change order
The test is the contract documents. If the item was not shown or specified at bid time, added work is a change. If your proposal clearly excluded the item, and the subcontract carried that exclusion, it is a change. Check that your exclusions made it into the signed subcontract. A proposal the contract does not reference may not protect you.
When a missed item is not a change order
If the item was in the documents and you did not count it, you own it. The same is true for an addendum you did not read. Many subcontracts bind the sub to all of the contract documents for its trade. A takeoff error is the estimator's cost, not the owner's.
How to protect yourself
- List the drawings, the spec sections and the addenda in your proposal.
- Write specific exclusions.
- Read the subcontract scope exhibit against your proposal before you sign.
- Give written notice as soon as you see a change. Contracts set notice deadlines.
- Do not start changed work without written direction.
- Keep your takeoff. It shows what you priced.
Contract terms differ by job and by state. For a dispute, read your contract and ask a construction attorney.
Bidding and estimating · Updated 11 Nov 2026