The bill came in over the contract — what a written change order clause actually decides

The clause is doing two jobs at once, which is why it fails so often. It is a pricing control — the owner wants the number before committing — and an evidentiary rule, deciding whose account of a site conversation wins. Courts enforce the second readily. They are far less willing to use it to hand an owner work it asked for and received, for nothing.

Three instruments, and only one of them needs both signatures

Standard forms already anticipate the standoff. Under AIA A201–2017 § 7.1.1 a change can be made three ways. A change order under § 7.2.1 is signed by owner, contractor and architect and states the change, the adjustment to the contract sum and the adjustment to the contract time. A construction change directive under § 7.3.1 is signed by the owner and architect only and directs the change *before* the price is agreed: the contractor must proceed under § 7.3.6 and the money follows. A minor change is ordered by the architect alone, and § 7.4 makes a contractor who proceeds with one, without giving notice that the sum or time is affected, waive the claim. Most of these disputes are avoidable here and are not, because nobody reaches for the middle instrument.

Waiver by course of conduct: when the owner’s own behaviour defeats the clause

The commonest way a written-only clause loses is that the parties spent nine months ignoring it. Where extras were repeatedly directed, performed, invoiced and paid with no form in sight, the owner is asking a court to enforce a requirement it dispensed with itself. California puts that to a jury in CACI 4522: the contractor must show the owner freely and knowingly relinquished the requirement, and "a waiver may be oral or written or may arise from conduct". The standard is clear and convincing evidence — which is why one unanswered email is thin and a paid history of unsigned extras is not.

Authority is the other half. In *Patriot Constr., LLC v. VK Elec. Servs., LLC*, 290 A.3d 1108 (Md. App. 2023) a project manager orally directed a subcontractor to perform extra work although he was not the person the subcontract named as able to approve modifications. The Appellate Court of Maryland let the recovery stand: he had negotiated the subcontract, was the sole day-to-day contact and had never treated written authorisation as a condition. Apparent authority comes from the principal’s conduct. It does not always run the contractor’s way — an Iowa appeal in 2022 held a guaranteed-maximum-price contractor to its unsigned change orders on work the owner had orally requested.

The change nobody called a change

A constructive change is extra work nobody labelled as extra: a rejected submittal forcing a costlier method, an inspector’s reading of a drawing, an instruction to sequence the job differently. Federal construction contracts write the doctrine down. FAR 52.243-4(b) treats "any other written or oral order" that causes a change as a change order, provided the contractor gives written notice identifying the date, circumstances and source. The price of that is in the same clause: nothing recoverable that was incurred more than 20 days before the notice, and the right asserted within 30 days. Private contracts rarely name the doctrine but reproduce its mechanics in their claim provisions, and the working rule is identical — the belief that an instruction has changed the work has to leave your head and land in writing the same day.

Differing site conditions, and the notice you give before digging further

What sits under a slab or behind a wall is the one variable neither side priced, and the standard allocation splits it in two. FAR 52.236-2 covers subsurface or latent conditions differing materially from those indicated in the contract, and unknown conditions of an unusual nature differing materially from those ordinarily encountered in work of that character. A201 § 3.7.4 mirrors it for private work. The first is a documents question; the second is an industry-expectation question, and much harder to win.

Both hang on a trigger that is not a deadline in the ordinary sense: notice is due before the conditions are disturbed. Break out the unexpected footing and photograph the rubble afterwards and the evidence is gone — and under FAR 52.236-2(c) no adjustment is allowed at all without the notice.

Allowances and unit prices: the number that was never a price

This is where the homeowner’s surprise usually comes from, and it is not extra work at all. An allowance is a placeholder for something not yet chosen, and A201 § 3.8.2 draws its edges narrowly: it covers the contractor’s cost of materials and equipment delivered to site plus required taxes, less trade discounts. Installation labour, overhead and profit sit in the contract sum but outside the allowance. A $6,000 tile allowance spent on $8,000 of tile therefore does not produce a $2,000 overrun — it produces $2,000 plus the extra cost of laying it, adjusted by change order either way.

Unit prices behave differently. A rate agreed per cubic yard is a price for a quantity nobody knew, so the quantity moving is not by itself a change. A201 § 9.1.2 reopens the rate only where quantities are "materially changed" so that applying it "causes substantial inequity".

What "cost" means, and why time is priced alongside it

Time is the half people forget, and the expensive half. A201 § 7.2.1 puts the adjustment to the contract time inside the change order alongside the money. One signed with the figure filled in and the days left blank is, on its face, an agreement that the work absorbs no delay — and where the contract carries liquidated damages, the contractor has just bought them.

On a house, the statute usually beats the clause

Residential home-improvement work is regulated separately in most states, and those rules point the other way: they exist to protect the homeowner, and they put the paperwork risk on the contractor.

• California. Business and Professions Code § 7159 applies above $500 and requires the contract and any changes to be in writing and signed before work commences. A change order becomes part of the contract only if signed in advance, and must give the scope, the cost added or subtracted, and the effect on the schedule of progress payments.
• New Jersey. N.J.A.C. 13:45A-16.2 requires every home improvement contract over $500 and "all changes in the terms and conditions thereof" to be in writing and signed by all parties — a consumer-fraud regulation, so a breach reaches the Consumer Fraud Act.
• New York. General Business Law § 771 requires a home improvement contract "and all amendments thereto" to be evidenced by a writing signed by all the parties.
• Virginia. 18VAC50-22-260 makes "failure to obtain written change orders, which are signed by both the consumer and the licensee" a prohibited act carrying licence consequences.

The relief valve matters as much as the rule. California’s § 7159 adds that failing to comply "does not preclude the recovery of compensation for work performed based upon legal or equitable remedies designed to prevent unjust enrichment". A homeowner who directed the work and now points at the missing form is usually arguing about the *measure* of what is owed. But not every state writes that saving in, and the same failure can be an independent consumer-protection violation.

What each side should take from this

For the homeowner holding the surprise invoice: the clause is worth something, but less than it reads. Ask three questions. Was this inside the original scope, or genuinely additional? Did I, or someone I let run the job, direct it? Have I already paid unsigned extras here? If the answers are additional, yes and yes, the argument is about price rather than liability — so ask in writing for the itemised basis of the charge, and send a demand only where the numbers do not survive it.

For the contractor holding the unpaid extra: everything you need existed on the day and nowhere else. Waiver is provable, apparent authority is provable, a constructive change is provable — each out of a contemporaneous record, none out of a recollection produced eight months later. The fix is administrative rather than legal, and cheap. One email on the day, a directive where the price will take a week, and a change order that fills in time as well as money. Projects that do this argue about how much. Projects that do not argue about whether, which costs more than the tile did.