What Are Latent Conditions?

Latent conditions turn up most often in groundwork and refurbishment, where what actually exists on site can differ from what the drawings and site history suggested. Common examples include:

• Unexpected rock or hard material encountered during excavation that was not indicated by available geotechnical information.
• Contaminated or unsuitable ground, such as fill containing debris, chemical contamination, or soil unable to bear the design loads.
• Groundwater at a level or volume not indicated by prior site investigation.
• Unrecorded or incorrectly located underground services — power, water, gas, telecommunications — not shown on any available service plan.
• Existing structures, footings or foundations from a previous building that were not documented and are only discovered during demolition or excavation.
• Hazardous materials, such as asbestos, found in an existing structure during refurbishment or demolition work.

Who bears the cost and time impact of a latent condition depends entirely on the contract — there is no universal rule. Many widely used commercial standard forms allocate the risk of a genuine latent condition to the client (the principal), on the basis that the contractor priced the job on the information the client made available, and it is not reasonable to expect the contractor to have priced for something nobody could have known about.

Other contract structures — particularly some design-and-construct or fixed-price residential arrangements — push more of the site risk onto the contractor, on the basis that the contractor took responsibility for its own site investigation as part of a fixed price. The table below is a general illustration only; the specific clause in your contract always governs.

A latent conditions claim generally starts the moment the contractor becomes aware of a condition it believes qualifies. Most contracts require written notice within a strict, often short, timeframe — sometimes just a matter of days — describing the condition and, where possible, before it is disturbed or covered up, so it can be independently verified.

The superintendent or client’s representative then assesses the claim against the reasonable foreseeability test: what information was available at tender, and could a competent contractor have anticipated the condition from it. If the claim is accepted, the additional time and cost are typically dealt with as a variation, priced against existing contract rates where they apply and by a fair and reasonable rate where they do not.

Because the reasonable foreseeability test looks back at what information was available at tender, the strength of a contractor’s due diligence before pricing the job directly affects both sides later. Thorough site investigation — geotechnical reports, service location searches, a proper physical inspection and a review of any available site history — genuinely reduces the risk of a costly surprise, and it also strengthens a contractor’s position if a real latent condition is later found.

Clients benefit from the same diligence: providing a complete and accurate set of site information at tender narrows what can later be argued as "unforeseeable," while gaps or omissions in that information tend to shift more risk toward the client if something unexpected turns up.

The contractor is responsible for identifying a suspected latent condition, documenting it — photographs and, where relevant, an independent report are valuable evidence — and giving notice within the contractual timeframe. The superintendent, principal’s representative or client then assesses the claim, often with input from a geotechnical engineer or other relevant consultant where the condition is technical in nature.

On larger projects, a quantity surveyor may be engaged to independently value the time and cost impact once the claim is accepted, in much the same way variations generally are assessed and priced.

Latent conditions sit alongside several related concepts, and it helps to keep them distinct:

• Latent conditions vs variation — a latent condition is one specific trigger for a variation; the variation itself is the mechanism used to price and time-adjust the resulting change in scope.
• Latent conditions vs patent defects — a patent condition or defect is one that is visible or reasonably discoverable at the relevant time; a latent condition, by definition, is not.
• Latent conditions vs provisional sums — a provisional sum is a known allowance for work that is not yet fully designed; a latent condition is an unknown, unpriced physical condition discovered only once work is under way.

Most latent conditions disputes trace back to a handful of avoidable missteps:

• Not documenting the condition — with photographs or an independent report — before it is disturbed or covered over, leaving little evidence to support the claim later.
• Missing the contractual notice period, which can forfeit the right to claim regardless of how genuine the condition was.
• Assuming any unexpected issue automatically qualifies as latent, without checking it against the reasonable foreseeability test and the information that was actually available at tender.
• Incomplete or inaccurate site information provided to tenderers, which widens what a contractor can later argue was unforeseeable.
• Treating a latent conditions claim informally, rather than raising and pricing it through the contract’s formal variation process.