During Construction
Your builder found something unexpected. What should happen next?
Almost every renovation runs into something nobody could see. The discovery isn't the problem — what happens in the next 48 hours is.
The correct sequence is: stop that work, get it assessed by whoever is qualified to assess it, put the fix in writing with a price and a schedule impact, and do not proceed until you approve it. Any step skipped is where projects go wrong.
The sequence that should happen
Work stops in that area
Not the whole job necessarily — but nothing gets covered up, and nothing gets built on top of the unknown while somebody decides what to do.
Somebody qualified assesses it
If it is structural, that means the engineer of record, not the crew's opinion and not the builder's. If it is soils, the geotechnical report governs. The point of calling them is that their answer is defensible to the building department later.
You get it in writing, with a price and a schedule impact
Both numbers. A change order with a cost but no timeline impact is half an answer, and on a job you are financing or living around, schedule is often the expensive half.
You approve it before work resumes
This is the step that protects you. If work has already happened, you were never offered the choice.
What this looks like in practice
On a room addition we're building in Milpitas, the approved plans called for building on an existing concrete slab. Cutting into it to dig the piers showed it was an unengineered slab poured over an old patio — sand between the pours, effectively no reinforcement, edges crumbling into loose soil.
We stopped, called the structural engineer of record, and he directed full removal and a rebuilt building pad. That went to the owners as a written, priced change order and did not proceed until they signed. There was a knock-on effect too: because the plans said we were working with existing construction, no property survey had been required — and once the slab was gone, the layout reference went with it, so a licensed surveyor had to come back out.
See the photos of what was under that slab →
The conversation that should have happened earlier
A builder who has done the work can usually tell you which part of your specific project carries the most unknown — the foundation, the panel, what's behind a particular wall. On the Milpitas job we told the owners at the start that the foundation was the likeliest place to find something. When it happened, it was a conversation they had already been prepared for rather than a surprise.
Hidden condition, or something that should have been caught?
| What happened | How to read it |
|---|---|
| Genuinely concealed — only visible once something was opened up | This is a real hidden condition. It is nobody's fault and it is what allowances and contingency exist for |
| Visible on a walkthrough, but nobody looked | Different conversation. A competent pre-construction walkthrough should have found it, and pricing it as a change order is weak |
| In the plans, but misread | That is a coordination failure, not a discovery |
| Discovered, then covered up without telling you | The serious one. If you suspect it, stop and get an independent look before anything else is built on top |
What you should insist on
- Photographs of the condition, taken before it is disturbed further. On the Milpitas job we measured and photographed the slab edge on the spot — that is what went to the engineer and into the change order.
- The name of whoever assessed it and what they directed.
- A written change order with cost and schedule, signed before work resumes.
- An explanation you can actually follow. If nobody will explain it in plain language, that is a signal in itself.
Common questions
What is a hidden or concealed condition in construction?
Should work stop when something unexpected is found?
Who should assess an unexpected structural condition?
Do I have to pay for a hidden condition?
Where to go next
Written by the team at Elusive Construction, a licensed California general contractor (B #1112902) building in Santa Clara and San Mateo counties. General information about how residential construction works — not legal advice. For your specific contract, talk to an attorney.
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