Finance

What is sunk cost in construction?

A sunk cost is money already spent that you cannot get back no matter what you decide next, like labor installed, nonreturnable material, or estimating hours on a bid you lost.

An office manager and contractor review invoices with a calculator and laptop in a construction office.
Review invoices, committed costs, and cash timing together before making project decisions. AI-generated illustration.

A sunk cost is a cost that has already been incurred and cannot be recovered. On a construction job that includes crew hours already worked, custom material already fabricated, permit fees already paid, and design fees already billed. The key idea: since that money is gone either way, it should not change what you do next. Only future costs and future revenue should.

That sounds obvious on paper. In practice, sunk costs pull at owners and PMs all the time. "We already have $60,000 into this job" is a feeling, not a reason to keep going.

How sunk cost works on a real job

Say a concrete sub is three weeks into a $210,000 site package. A layout error put a section of footings in the wrong place. The crew has spent $18,000 in labor and $9,000 in concrete on the bad work. The foreman suggests building a workaround that saves the footings but adds $14,000 in extra forming and engineering. Tearing out and repouring would cost $16,000.

Example: deciding what to do about misplaced footings
OptionFuture costSunk cost
Engineered workaround$14,000 plus design risk$27,000 already spent
Tear out and repour$16,000$27,000 already spent

The $27,000 is in the same column for both options, so it does not help pick one. The real comparison is $14,000 plus risk against $16,000 with no risk. If the workaround needs a redesign review that could delay the slab two weeks, repouring may be the better call even though it "wastes" the original work. The job cost report will show the loss either way.

Where sunk costs show up for contractors

  • Lost bids. Estimating hours, plan room fees, and takeoff time on a job you did not win. They are overhead now, not a reason to chase a bad project on rebid.
  • Losing jobs. When cost to complete shows a job will lose money, the money spent so far is irrelevant to whether you should finish. The contract usually decides that for you, but it matters for how much effort and how many change orders you push.
  • Equipment. A loader you bought for $120,000 is sunk. Whether to use it, rent it to others, or sell it depends on what it can earn or fetch from here.
  • Software and systems. Two years of setup in a tool that no longer fits is sunk. Staying for that reason alone keeps costing.
  • Preconstruction. Design-build firms often have large precon investments before a GMP is signed. If the owner balks, those hours are gone unless the contract pays for them.

Sunk cost versus related cost terms

Sunk cost is a decision concept, not an accounting line. It overlaps with actual cost (money spent to date) but adds a test: can you get any of it back? Returnable material sitting in the yard is spent but not fully sunk, because a restocking fee is less than the purchase price. A committed cost under a signed PO is not yet spent, but if cancellation terms are harsh it may be effectively sunk.

Common mistakes

  1. Throwing good money after bad. Continuing a failing approach because of what it already cost.
  2. Pricing to recover old losses. Adding last job's overrun to this job's bid makes you less competitive and does not get the money back.
  3. Counting sunk cost twice in a claim. In delay and change claims, owners and reviewers look for costs that would have been spent anyway. Only costs caused by the change belong in the number.
  4. Ignoring salvage. Before calling something sunk, check whether material can be returned, reused on another job, or sold.

Related terms

See estimate at completion, job costing, and indirect costs. Smart Business Automator shows spent-to-date and forecast cost to complete side by side on each job, which keeps sunk costs where they belong: in the history.

Frequently asked questions

Is sunk cost the same as a loss?

Not always. A sunk cost is any spent money you cannot recover. It becomes a loss when the job or decision does not earn it back.

Should sunk costs be included in a change order price?

Only costs actually caused by the change belong in a change order. Work already done that the change makes useless can be part of the price if the change is what wasted it, but document it carefully.

Are estimating costs on lost bids sunk?

Yes. They are part of company overhead and should be recovered through your overhead rate across all jobs, not loaded onto one future bid.

How do I avoid the sunk cost trap?

Compare options using only future costs and future revenue. Write the sunk amount down once, acknowledge it, and leave it out of the comparison.

Written and edited by

Maurice Francois writes and edits construction operations guides for Smart Business Automator. More from Maurice on the Scaling Legends podcast.

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