What happens when unforeseen conditions are found during construction?

Refurbishment and upgrade work on existing public buildings finds things nobody documented. That is the nature of buildings that have been altered several times over decades.

What turns up most often

**Services that are not where the drawings show them,** or that are live when they were recorded as abandoned.

**Asbestos** outside the register, which is its own process and covered under [asbestos in refurbishment](/answers/asbestos-in-school-refurbishment).

**Structure that does not match the documentation,** including footings at a different depth, slabs of a different thickness, and beams nobody recorded.

**Ground conditions,** meaning rock, fill, contamination or groundwater at a level the geotechnical information did not indicate.

**Previous work done poorly,** including concealed water damage, unsupported penetrations and non-compliant electrical work.

**Drainage that does not go where it was thought to go,** which is common on sites that have been extended repeatedly.

The first response

Stop the work in that area. Not the whole site, and not that work face.

Then record it properly: photographs, dimensions, levels, the date, and who found it. That record is what determines whether the matter is resolved in a week or argued about for months.

Then notify, in writing, within the period the contract requires. Notice periods for latent conditions are usually short and the right to claim can be lost by missing them, which is a contract administration discipline rather than a construction one.

Whether it is a latent condition

That depends on the contract and on the information provided at tender.

A condition is generally latent where it was not disclosed, could not reasonably have been identified by a competent contractor from the information available, and differs materially from what a contractor was entitled to assume.

A condition that was in the documents, or that an inspection during the tender period would have revealed, is usually the contractor's risk. Which is one of the reasons the [tender information](/answers/what-a-client-should-provide-at-tender) a client provides matters to the price as well as to the programme.

Reducing how often it happens

**A dilapidation survey and a proper site investigation before work starts,** which is the single most effective control.

**Service location by a qualified locator** rather than by drawing, before any excavation, which is covered under [service location](/answers/service-location-and-utility-relocations).

**Intrusive investigation where the risk is high,** meaning opening up a small area under a controlled process rather than discovering it during demolition.

**Reading the building's history,** including previous approvals, as-built drawings and the asbestos register, before pricing.

None of that eliminates the unknown in a sixty year old building. It reduces the number of times it stops the programme.

How it is resolved

The condition is assessed, the options are priced, the time effect is stated, and the client decides. That decision goes through the [variation](/answers/how-variations-are-managed) process with its own instruction rather than being absorbed quietly and argued about at the end.

On a live site the time effect is frequently the larger issue, because the work may be in a fixed holiday window.

Why the record matters most

Almost every dispute about a latent condition is a dispute about what was there and when it was found.

A contractor who photographs, dimensions, dates and notifies the same day is in a position to resolve it on the facts. One who mentions it verbally and keeps going has no position at all.