What is the 1-10-100 rule?
A defect that costs $1 to fix at source costs $10 once it is built in, and $100 once it has been delivered. The ratio is a quality-cost convention rather than a precise measurement, but the shape of it is structural — and in construction the escalation is unusually brutal, because the building is a sequence of concealments.
Why construction makes the ratio worse
Construction is a sequence of concealments. Concrete goes over rebar. Blockwork goes over waterproofing. Ceilings go over ductwork. Every trade that follows makes the last one harder to reach.
So the jump from $1 to $10 is not a metaphor about diligence — it is the cost of demolition and rebuild to get back to something that was visible and accessible a week ago. And the jump to $100 adds the things that only exist after handover: the occupied building, the disrupted tenant, the delay claim, the defects-liability dispute, the reputational cost of being the firm that built it.
What follows from it
The entire case for inspection sequencing, hold points and the observation layer is this ratio. An observation — someone noticing a deviation forming and photographing it with a due date — is the $1 intervention. It is the cheapest thing you will ever do, and almost nobody resources it properly.
It also explains why quality programmes that are measured only on defects found at handover are measuring the wrong end. By then everything found is a $100 problem. The number worth watching is how much you are catching while it is still $1.
And the total is larger than the rework line
The Get It Right Initiative puts the total cost of avoidable error at 10–25% of project cost once indirect and latent effects are counted — roughly seven times the UK sector’s annual profit.
That is a different measurement from the roughly 5% of contract value that gets directly reported as rework, and the two should never be read as two ends of one range. Most rework is never coded as rework, which is exactly why the total is so much larger than the line item.
References
- module: /modules/site-observations/ — the 1-10-100 quality-cost rule; Get It Right Initiative
Zepth is the construction project delivery platform — it runs construction, procurement and asset management on one record, and does the work: reading the drawings, reviewing the submittals, matching the invoices and flagging the risks, with a human sign-off on anything consequential.
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