Spearin Doctrine / Implied Warranty of Plans
A foundational legal doctrine, from a 1918 U.S. Supreme Court case, holding that when an owner provides a contractor with design plans and specifications, the owner impliedly warrants those plans are adequate, and the contractor isn't liable for defects that result from following them exactly as designed.
Why it matters
The doctrine shifts real financial liability away from whoever built the design and onto whoever designed it, so identifying whether a defect came from faulty design or faulty construction isn't just a technical question, it decides who actually pays.
On a real project
A retaining wall fails after being built exactly to the structural engineer's specified dimensions and reinforcement, and the Spearin doctrine places responsibility on the design professional whose plans were inadequate, not on the contractor who built precisely what was designed.
Who this matters most to
A Construction Attorney relies on the Spearin doctrine constantly when a contractor is blamed for a defect that traces back to the plans it was given rather than to its own workmanship.
Where this goes wrong
A contractor swaps in a slightly different fastener spacing than the plans specify, assuming the substitution is close enough not to matter, and the resulting failure traces back to that deviation rather than to the original design. Because the contractor didn't actually follow the plans as designed, the Spearin doctrine's protection doesn't apply, and the contractor bears the liability it assumed the design would have covered.