Reality Anchor: The Assumption Trap 解説

シナリオ

英国の測量士が、湿気対策や隠れた状態に関する未検証の前提により、物件のすべての欠陥に対して責任を問われた事例。

The surveyor inspected a property and noted that the rendered external walls appeared in good condition. Based on this visual observation alone, the surveyor assumed that adequate damp-proof membranes (DPMs) were present behind the render.

Critically, the surveyor did not recommend that the buyer obtain a Professional Consultant Certificate (PCC) from a specialist to verify the hidden damp-proofing system.

技術的エラー

The surveyor's error was treating a visual assumption as equivalent to verified fact. The rendered walls hid the true condition of the damp-proof membranes. Without invasive testing or specialist consultation, there was no way to confirm their presence or effectiveness.

This parallels coordinate/elevation errors in surveying: just because a measurement looks right on a plan doesn't mean the underlying data (datum, transformation, or physical monument) is correct. The surveyor failed to apply the principle: "If you can't see it, you can't certify it."

結末

After purchase, the buyer discovered extensive damp problems. The property required significant remedial work, far beyond what a simple DPM failure would suggest.

The Court of Appeal ruled:

• Surveyor Liable for All Defects: The surveyor was held responsible not just for the visible issues, but for all property defects that a proper investigation would have revealed.
• Inadequate Suspicion Trail: The court found that the surveyor should have been suspicious of hidden defects and recommended further investigation (PCC).
• Diminution in Value: Damages were calculated based on the full reduction in property value, not just the cost of the specific damp-proofing repair.

専門家への教訓

Assumptions Are Liabilities.